SIST-TP ISO/TR 18811:2019
Cosmetics - Guidelines on the stability testing of cosmetic products
Cosmetics - Guidelines on the stability testing of cosmetic products
This Standard gives guidelines for the stability testing of cosmetic products. It reviews readily available bibliographic references that provide a resource for the assessment of the stability of cosmetic products. This review of the available guidelines that assess the stability of cosmetic products can serve as a technical/scientific framework to identify the most suitable methods for the assessment of the stability of cosmetic products. This document does not aim to specify the conditions, parameters or criteria of stability testing. Considering the wide variety of cosmetic products, storage and use conditions, it is not possible to define a single way to assess product stability. Therefore, it is up to the manufacturer to specify and justify the stability protocol to cover test methods, specifications and conditions at which products will be tested.
Cosmétiques - Lignes directrices relatives aux essais de stabilité des produits cosmétiques
ISO/TR 18811:2018 fournit des lignes directrices pour les essais de stabilit� des produits cosm�tiques. Il examine des r�f�rences bibliographiques facilement accessibles qui offrent une ressource pour l'�valuation de la stabilit� des produits cosm�tiques. Cette revue des lignes directrices disponibles qui �valuent la stabilit� des produits cosm�tiques peut �tre utilis�e comme cadre technique/scientifique afin d'identifier les m�thodes les plus appropri�es pour l'�valuation de la stabilit� des produits cosm�tiques.
Le pr�sent document n'est pas destin� � sp�cifier les conditions, les param�tres ou les crit�res des essais de stabilit�.
Compte tenu de la grande diversit� des produits cosm�tiques, des conditions de stockage et d'utilisation, il est impossible de d�finir un moyen unique d'�valuer la stabilit� des produits. Par cons�quent, il appartient au fabricant de sp�cifier et de justifier le protocole de stabilit� r�gissant les m�thodes d'essai, leurs sp�cifications et les conditions dans lesquelles les produits seront soumis � essais.
Kozmetika - Smernice za preskušanje stabilnosti kozmetičnih izdelkov
Ta standard podaja smernice za preskušanje stabilnosti kozmetičnih izdelkov. Ponuja pregled nad lahko dostopnimi bibliografskimi referencami, ki zagotavljajo sredstvo za oceno stabilnosti kozmetičnih izdelkov. Ta pregled razpoložljivih smernic, ki ocenjujejo stabilnost kozmetičnih izdelkov, se lahko uporabljajo kot tehnični/znanstveni okvir za prepoznavanje najustreznejših metod za ocenjevanje stabilnosti kozmetičnih izdelkov. Cilj tega dokumenta ni opredeliti pogoje, parametre ali merila za preskušanje stabilnosti. Glede na raznolikost kozmetičnih izdelkov, pogoje skladiščenja in uporabe ni mogoče opredeliti enotnega načina ocenjevanja stabilnosti izdelkov. Zato mora proizvajalec opredeliti in utemeljiti protokol stabilnosti, ki zajema preskusne metode, specifikacije ter pogoje za preskušanje izdelkov.
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TECHNICAL ISO/TR
REPORT 18811
First edition
2018-02
Cosmetics — Guidelines on the
stability testing of cosmetic products
Cosmétiques — Lignes directrices relatives aux essais de stabilité des
produits cosmétiques
Reference number
ISO/TR 18811:2018(E)
©
ISO 2018
---------------------- Page: 1 ----------------------
ISO/TR 18811:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 18811:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic principles of cosmetic stability . 2
5 Aspects to be addressed during stability testing . 3
5.1 General . 3
5.2 Stage/scale of tested batches . 3
5.3 Test procedures and conditions . 4
5.3.1 Principle . 4
5.3.2 Temperature and humidity . 4
5.3.3 Cycling of temperature and/or humidity . 5
5.3.4 Vibration . 6
5.3.5 Centrifugation . 6
5.3.6 Exposure to light (photostability) . 6
5.4 Physical, physico-chemical and chemical alterations . 7
5.4.1 Physical destabilization phenomena of different product types . 7
5.4.2 Chemical destabilization processes . 8
5.4.3 Destabilization phenomena . 9
5.4.4 Specific test methods .10
5.5 Microbiological aspects .12
5.5.1 General.12
5.5.2 Microbiological parameters .12
5.5.3 Testing conditions .12
5.5.4 Microbiological specifications .13
5.5.5 Interpretation of results .13
5.6 Interaction with packaging .13
5.6.1 General information .13
5.6.2 Types of packing materials and main possible evaluations .13
5.6.3 Pressure vessels (aerosols) .14
6 Stability test conclusions .14
6.1 Evaluation .14
6.2 Report .14
Bibliography .15
© ISO 2018 – All rights reserved iii
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ISO/TR 18811:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 217, Cosmetics.
iv © ISO 2018 – All rights reserved
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ISO/TR 18811:2018(E)
Introduction
Stability studies are aimed at assessing the ability of a product to maintain the desired physical,
chemical and microbiological properties, as well as functionality and sensorial properties when stored
and used under appropriate conditions by the consumer. More simply, the objective of a stability study is
to determine the shelf life of a product and to evaluate whether a product in the package is stable when
subjected to the market conditions in which it is sold and used. The “market conditions” encompass
distribution (transportation), warehouse storage and conditions during use.
Thus, the stability study may be seen as a prerequisite for ensuring product quality. Stability tests on
cosmetic products are required for
— obtaining a guidance on the formulation of the product, and the appropriate packaging material,
— optimizing the formulation and manufacturing process,
— determining conditions of transportation, storage, display and manner of use,
— estimating and confirming shelf life, and
— ensuring customer safety.
This document identifies readily available references to assess the stability of cosmetic products on the
market. Its purpose is to provide a resource for the selection of the appropriate stability tests. Although
these guidelines provide a helpful starting point to evaluate new products and technologies, adapting
the testing to reflect differences between product types and formulations may still be necessary.
© ISO 2018 – All rights reserved v
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TECHNICAL REPORT ISO/TR 18811:2018(E)
Cosmetics — Guidelines on the stability testing of cosmetic
products
1 Scope
This document gives guidelines for the stability testing of cosmetic products. It reviews readily
available bibliographic references that provide a resource for the assessment of the stability of cosmetic
products. This review of the available guidelines that assess the stability of cosmetic products can
serve as a technical/scientific framework to identify the most suitable methods for the assessment of
the stability of cosmetic products.
This document does not aim to specify the conditions, parameters or criteria of stability testing.
Considering the wide variety of cosmetic products, storage and use conditions, it is not possible to
define a single way to assess product stability. Therefore, it is up to the manufacturer to specify and
justify the stability protocol to cover test methods, specifications and conditions at which products will
be tested.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
accelerated stability evaluation
study designed to speed up naturally occurring destabilization processes due to intrinsic or extrinsic
factors and which predicts the behaviour over the long term
Note 1 to entry: Typically, physico-chemical, mechanical or thermal procedures are employed.
3.2
real time stability evaluation
study that monitors the state of a product to determine the time course of any alteration to it under
reasonably expected conditions of storage and use
Note 1 to entry: Often called “long term test” or “standard stability test”.
3.3
stability
ability of a cosmetic product to resist change or variation of its initial properties over time under stated
or reasonably foreseeable conditions of storage and use
Note 1 to entry: See Reference [1].
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ISO/TR 18811:2018(E)
3.4
stability criteria
deviations from initial properties or behaviour at production state, which are acceptable
Note 1 to entry: See Reference [1].
3.5
stability metrics
properties/parameters of the state or behaviour of a cosmetic product which should be monitored
according to demanded, specific product qualities
Note 1 to entry: See Reference [1].
3.6
shelf life
recommended time period that a cosmetic product can be kept after its production, during which the
defined quality of the product remains acceptable under expected conditions of distribution, storage,
display and usage
Note 1 to entry: See Reference [1].
4 Basic principles of cosmetic stability
Design, formulation and the manufacturing process of cosmetic products have to fulfil general and
specific demands and requirements of distribution pathways, and especially of customers. Specification,
functionality and aesthetics have to be preserved, i.e. have to be stable, over the entire life cycle of a
product.
Processed cosmetic products are complex matrixes which undergo spontaneous alterations to reach the
[2]
free energy minimum in accordance with the second thermodynamic law. These so-called intrinsic
[3]
causes may be of physical, physico-chemical or chemical origin. Many reactions and processes may
lead, under the condition of the “market”, to a deviation from the initial, original product properties
at the date of manufacturing. Departure may be caused by thermodynamically driven internal or
[1] [4][5] [6]
externally driven effects, microbiological impact or interactions with packaging and may
finally lead to a loss of specified product functionality or/and aesthetic attributes. This impacts
usability, shelf life and marketability. Destabilization processes of the original product may also be
provoked, enhanced or magnified due to extrinsic (external) factors. For example, state changes may
be triggered by thermal energy loss or gain, light and UV irradiation, mechanical energy input (such
as vibration or pressure), oxygen uptake, humidity, interaction by or with container/closure system
[3]
(packaging), and proliferation of microorganisms.
Cosmetics are of different natures and some consist of several phases, dispersed ones and a continuous
one, and may be classified as suspensions or emulsions. Suspensions are solid particles dispersed in a
liquid phase. Emulsions are composed of two liquid phases, typically oil-in-water (o/w) or water-in-oil
(w/o). Cosmetic dispersions are usually very complex and may contain several phases.
A stability test aims at providing information on the state/behaviour of the cosmetic products in
the container/enclosure under the different conditions to which they may be subjected from their
[7][8][9]
manufacturing date until the end of their recommended period of use. The state of a cosmetic
product and its stability depend upon numerous interrelated physical, physico-chemical and chemical
parameters as well as interaction with environment, and its nature is therefore very complex. In
general, they may be roughly classified as mechanical-driven, thermal- or diffusion-driven, interaction-
[1][7][10][11]
force- driven or externally provoked processes. There is no universal method or technique to
quantify all stability aspects due to the complexity of different pathways of destabilization. Therefore,
it is always necessary to specify precise stability metrics and acceptance criteria.
After determination of the stability metric(s), it is necessary to select appropriate stability test methods
to monitor the alteration of the product over time. It is recommended to select methods that do not
require sample preparation (e.g. dilution) and quantify kinetics of the product destabilization based
[1]
on defined metric(s) in a direct way. Real time measurements can be made by traditional visual
2 © ISO 2018 – All rights reserved
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ISO/TR 18811:2018(E)
observations, sensory techniques or use of different measuring techniques which are advantageous
[1]
in being quantitative, objective, traceable, reproducible and retrievable. Scanning and spatially
resolving techniques are appropriate in particular to detect phase separation and help to discriminate
[1][7][10][11]
between phase separation and phase changes.
In the case of very stable products, analytical techniques having high resolution/sensitivity should be
used and procedures can be required in order to accelerate the alteration to shorten the detection time
[1][11]
to meet the predefined stability criteria. Typical acceleration approaches are mechanical ones
(e.g. high gravity by centrifugation) or elevated storage temperatures for a given time. Preservation
[3]
efficacy testing (challenge-test) aims to test microbiological attributes under accelerated conditions.
[5]
However, because of the interrelated physical, physico-chemical and chemical properties of cosmetic
emulsions or suspensions, adequate acceleration methods may be chosen and verified in the context of
[1][11]
a specific product.
Beside direct methods, correlative test methods are utilized focusing on determination of a single
[1]
parameter of the state of a product that is known to correlate with product stability. Typical
parameters measured and compared with pre-defined acceptable values are, for example, mean
particle/droplet size or zeta-potential. These quantities reflect the state at the time of the measurement
and do not yield kinetic information. Such test procedures may be used for quality assessment of a
specified product but, due to the complexity of the state of cosmetic products, currently no theoretical
basis exists to predict the time course of any product alteration based on a single parameter obtained
at any single time point. In addition, most of these measuring techniques demand sample preparation
[1]
and often product dilution.
Due to the cosmetic product formulation’s complexity overall, caution should be employed in stability
assessment and predicting its shelf life, and the properties of the constituents should be considered and
[11]
understood, as well as the product’s behaviour and the factors which influence it.
5 Aspects to be addressed during stability testing
5.1 General
The key aspects to consider when assessing the stability of cosmetics products are listed in 5.2 to 5.6.
Guidance is provided based on the review of relevant sources cited in the text.
5.2 Stage/scale of tested batches
When working on a brand new product (new formula, new manufacturing process, new packaging) and
therefore where no significant body of knowledge is available, it might be appropriate to carry multiple
independent stability studies, usually referred as “preliminary tests”. It is up to the manufacturer to
decide on the number of batches, the scale of their manufacture that are subject to stability testing and
[7][12][9][13]
at what stage of the project development cycle this takes place.
The stability of the final product (final formula, final manufacturing process, final packaging) may be
demonstrated before its commercialization. Accelerated stability evaluation may be conducted prior to
commercialization to predict product shelf life. Following commercialization, the shelf life confirmation
is obtained by long term stability testing on representative formulations.
Minor variations between products subjected to stability testing versus final commercial product can
be acceptable if they are deemed as not having an impact on product characteristics and integrity, but
[9]
need to be documented and justified.
Common acceptable practices include but are not limited to
— usage of formulation samples from the development stage for preliminary tests,
— usage of pilot batches instead of production scale, for some specific non-scale up products and where
[13][14]
the manufacturing process is considered equivalent, and
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ISO/TR 18811:2018(E)
— usage of unlabelled packaging, or packaging of different shape, when packaging size, closure system
and material remain unchanged, or when decorative material remains of same nature but with
different design (e.g. same ink versus different print).
[14]
Additionally, matrixing and bracketing are acceptable practices but should be documented and
justified to ensure that the stability study protocol will cover the entire product portfolio and provide
[13][14][15]
enough information (e.g. multiple shade, packaging size).
5.3 Test procedures and conditions
5.3.1 Principle
The general objective of a stability test is to determine whether a given product, in the container in
which it is being marketed, has an adequate shelf life, under the conditions of the market in which it is
[16]
being sold.
Stability testing may be of sufficient duration to cover storage, shipment and subsequent use, and to
guarantee safety and quality.
Manufacturers may, for each formula type, select the pertinent test criteria according to their experience
and evaluate these test criteria at one or more temperatures.
Because of the wide variety of cosmetic products and their inherent complexity, standard stability tests
[7]
cannot always be prescribed. Both real time and accelerated test procedures are used to provide
the desired information. Most cosmetics, due to their short development cycles, require accelerated
test protocols to help predict stability parameters in a shorter period of time. To achieve these end
points, some samples are kept under test conditions designed to accelerate changes that may occur and
some are stored at normal conditions. Test conditions refer to the various manufacturing or storage
[10]
conditions (e.g. batch) or combination of conditions (e.g. container closures) to be studied. The
recommended shelf life may be estimated by accelerated stability tests and can be confirmed by real
[13]
time (long term stability) tests.
While shelf life is determined by the stability of the product, the overall stability profile is made up of
several components, such as
— the inherent chemical and physical stability of the product, and
— the possible interactions between the product (contents) and its primary packaging.
In order to generate the desired information recommended, standard/long term and accelerated test
parameters are outlined in 5.3.2 to 5.3.6.
5.3.2 Temperature and humidity
NOTE See References [10] and [16].
Accelerated and long term conditions can be used. The long term condition is conducted at regular
storage conditions (e.g. controlled room temperature), while the accelerated testing is conducted under
stress conditions (e.g. elevated temperature) which aims to increase the rate of potential degradation.
[3][7][8][9][10][12][13][16]
Throughout this document it is assumed that all temperature and humidity storage conditions might
experience a variation, for example ±3 °C and ±5 % RH.
Accelerated test conditions may vary and should be established based on correlations to real time
storage conditions for the specific region or market. References to commonly used accelerated test
conditions for testing cosmetic products are provided in the Bibliography. The temperature used and
[3][7][10][13][16][17][18][19]
the duration will depend on the product type.
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ISO/TR 18811:2018(E)
Samples stored at elevated temperatures represent a more constant degree of acceleration and
render stability predictions as being more accurate. Cosmetic stability guidelines list various storage
[3][16][17][19]
conditions and durations for accelerated stability testing:
— (30 ± 2) °C;
— (37 ± 2) °C;
— (40 ± 2) °C;
— (45 ± 2) °C;
— (50 ± 2) °C.
[16]
Durations range from one week to three months. Relative humidity may be ambient or controlled,
[9][17]
such as 37 °C to 40 °C/75 % to 80 % RH.
Alternative temperature and humidity conditions may be used, including an intermediate condition of
[9][14][20]
(30 ± 2) °C and 65 % RH. Test conditions and durations may be adjusted where justified to
[9][18]
cover the product’s distribution and storage conditions.
Instability can be caused by either chemical reactions or physical processes and often a combination of
both. These alterations proceed at a faster rate at higher temperatures but the degree of acceleration
is variable as it depends on the specific rate constants, which are often unknown. Care should be taken
in the interpretation of results when using temperatures far removed from ambient, as the observed
changes may never occur at normal in market temperatures. Use of moderate elevated temperature, e.g.
[10][17]
37 °C to 40 °C, is a more realistic condition for predicting in market stability.
Tests at low or elevated relative humidity are normally tests of the package and not of the product.
They serve either to show the effect of storage at varying humidity on the container or as a measure of
the barrier properties of the container. Products may be adversely affected by atmospheric humidity
but if this happens in the product in its sale package it indicates that the package provides inadequate
protection from the atmosphere.
Tests at elevated humidity are less likely to accelerate changes at normal storage conditions compared
to tests at elevated temperatures and ambient humidity. If absorption of water vapour presents a risk to
the packaged product’s properties, then testing at elevated humidity may accelerate changes. If the risk
is loss of water or other volatile constituents (such as in permeable packaging), then elevated humidity
may actually retard changes, and testing at low humidity may be more appropriate.
It may be appropriate to consider low temperature storage during stability testing.
— Refrigeration at 5 °C (2 °C to 8 °C) / ambient humidity: This condition may be used to store samples
[3]
to be used as reference samples.
— Freezer at −5 °C to −10 °C: This condition may be used to determine the effects of extreme low
[3]
temperature, for example during transportation.
5.3.3 Cycling of temperature and/or humidity
Tests in which the temperature and/or humidity are changed at regular intervals, and which subject
the package to variations other than static stresses, are sometimes more severe tests than continuous
storage at one condition. These tests provide evidence of emulsion stability, tendency to crystallization,
deposition or clouding, and whether the reaction is reversible. This data are also applicable to
determining how robust a product is to extreme fluctuations in temperature during distribution and
[3][10][16][19]
storage.
Freeze/thaw tests are applicable to
— liquid products as a measure of the potential to develop crystallization or cloud formation, and
— emulsions or creams as an indicator of emulsions stability.
© ISO 2018 – All rights reserved 5
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ISO/TR 18811:2018(E)
Freeze/thaw tests may be carried out on all solutions, emulsions, creams and all other liquid or
semi-solid products. These tests provide evidence of emulsion stability, tendency to crystallization,
deposition or clouding, and whether the reaction is reversible.
Typical conditions for freeze/thaw cycling are: 12 h to 24 h at freezing temperatures (e.g. −5 °C)
followed by 12 h to 24 h at thawing temperatures (e.g. 25 °C) or elevated temperatures (e.g. 45 °C) for a
[10] [3]
specified number of cycles. Suggested cycling conditions include the following limits:
— 24 h at (25 ± 2) °C and 24 h at (−5 ± 2) °C;
— 24 h at (40 ± 2) °C and 24 h at (4 ± 2) °C;
— 24 h at (45 ± 2) °C and 24 h at (−5 ± 2) °C;
— 24 h at (50 ± 2) °C and 24 h at (−5 ± 2) °C.
[3]
The number of cycles may vary, for example six cycles can be used.
5.3.4 Vibration
Testing is conducted in order to examine the changes in quality under severe conditions that may be
encountered during distribution such as temperature extremes, shipping and light. One example of
stress testing would be vibration tests. Vibration tests may be needed to determine if emulsions or
powders are going
...
SLOVENSKI STANDARD
SIST-TP ISO/TR 18811:2019
01-november-2019
Kozmetika - Smernice za preskušanje stabilnosti kozmetičnih izdelkov
Cosmetics - Guidelines on the stability testing of cosmetic products
Cosmétiques - Lignes directrices relatives aux essais de stabilité des produits
cosmétiques
Ta slovenski standard je istoveten z: ISO/TR 18811:2018
ICS:
71.100.70 Kozmetika. Toaletni Cosmetics. Toiletries
pripomočki
SIST-TP ISO/TR 18811:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST-TP ISO/TR 18811:2019
---------------------- Page: 2 ----------------------
SIST-TP ISO/TR 18811:2019
TECHNICAL ISO/TR
REPORT 18811
First edition
2018-02
Cosmetics — Guidelines on the
stability testing of cosmetic products
Cosmétiques — Lignes directrices relatives aux essais de stabilité des
produits cosmétiques
Reference number
ISO/TR 18811:2018(E)
©
ISO 2018
---------------------- Page: 3 ----------------------
SIST-TP ISO/TR 18811:2019
ISO/TR 18811:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 4 ----------------------
SIST-TP ISO/TR 18811:2019
ISO/TR 18811:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic principles of cosmetic stability . 2
5 Aspects to be addressed during stability testing . 3
5.1 General . 3
5.2 Stage/scale of tested batches . 3
5.3 Test procedures and conditions . 4
5.3.1 Principle . 4
5.3.2 Temperature and humidity . 4
5.3.3 Cycling of temperature and/or humidity . 5
5.3.4 Vibration . 6
5.3.5 Centrifugation . 6
5.3.6 Exposure to light (photostability) . 6
5.4 Physical, physico-chemical and chemical alterations . 7
5.4.1 Physical destabilization phenomena of different product types . 7
5.4.2 Chemical destabilization processes . 8
5.4.3 Destabilization phenomena . 9
5.4.4 Specific test methods .10
5.5 Microbiological aspects .12
5.5.1 General.12
5.5.2 Microbiological parameters .12
5.5.3 Testing conditions .12
5.5.4 Microbiological specifications .13
5.5.5 Interpretation of results .13
5.6 Interaction with packaging .13
5.6.1 General information .13
5.6.2 Types of packing materials and main possible evaluations .13
5.6.3 Pressure vessels (aerosols) .14
6 Stability test conclusions .14
6.1 Evaluation .14
6.2 Report .14
Bibliography .15
© ISO 2018 – All rights reserved iii
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SIST-TP ISO/TR 18811:2019
ISO/TR 18811:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 217, Cosmetics.
iv © ISO 2018 – All rights reserved
---------------------- Page: 6 ----------------------
SIST-TP ISO/TR 18811:2019
ISO/TR 18811:2018(E)
Introduction
Stability studies are aimed at assessing the ability of a product to maintain the desired physical,
chemical and microbiological properties, as well as functionality and sensorial properties when stored
and used under appropriate conditions by the consumer. More simply, the objective of a stability study is
to determine the shelf life of a product and to evaluate whether a product in the package is stable when
subjected to the market conditions in which it is sold and used. The “market conditions” encompass
distribution (transportation), warehouse storage and conditions during use.
Thus, the stability study may be seen as a prerequisite for ensuring product quality. Stability tests on
cosmetic products are required for
— obtaining a guidance on the formulation of the product, and the appropriate packaging material,
— optimizing the formulation and manufacturing process,
— determining conditions of transportation, storage, display and manner of use,
— estimating and confirming shelf life, and
— ensuring customer safety.
This document identifies readily available references to assess the stability of cosmetic products on the
market. Its purpose is to provide a resource for the selection of the appropriate stability tests. Although
these guidelines provide a helpful starting point to evaluate new products and technologies, adapting
the testing to reflect differences between product types and formulations may still be necessary.
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TECHNICAL REPORT ISO/TR 18811:2018(E)
Cosmetics — Guidelines on the stability testing of cosmetic
products
1 Scope
This document gives guidelines for the stability testing of cosmetic products. It reviews readily
available bibliographic references that provide a resource for the assessment of the stability of cosmetic
products. This review of the available guidelines that assess the stability of cosmetic products can
serve as a technical/scientific framework to identify the most suitable methods for the assessment of
the stability of cosmetic products.
This document does not aim to specify the conditions, parameters or criteria of stability testing.
Considering the wide variety of cosmetic products, storage and use conditions, it is not possible to
define a single way to assess product stability. Therefore, it is up to the manufacturer to specify and
justify the stability protocol to cover test methods, specifications and conditions at which products will
be tested.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
accelerated stability evaluation
study designed to speed up naturally occurring destabilization processes due to intrinsic or extrinsic
factors and which predicts the behaviour over the long term
Note 1 to entry: Typically, physico-chemical, mechanical or thermal procedures are employed.
3.2
real time stability evaluation
study that monitors the state of a product to determine the time course of any alteration to it under
reasonably expected conditions of storage and use
Note 1 to entry: Often called “long term test” or “standard stability test”.
3.3
stability
ability of a cosmetic product to resist change or variation of its initial properties over time under stated
or reasonably foreseeable conditions of storage and use
Note 1 to entry: See Reference [1].
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3.4
stability criteria
deviations from initial properties or behaviour at production state, which are acceptable
Note 1 to entry: See Reference [1].
3.5
stability metrics
properties/parameters of the state or behaviour of a cosmetic product which should be monitored
according to demanded, specific product qualities
Note 1 to entry: See Reference [1].
3.6
shelf life
recommended time period that a cosmetic product can be kept after its production, during which the
defined quality of the product remains acceptable under expected conditions of distribution, storage,
display and usage
Note 1 to entry: See Reference [1].
4 Basic principles of cosmetic stability
Design, formulation and the manufacturing process of cosmetic products have to fulfil general and
specific demands and requirements of distribution pathways, and especially of customers. Specification,
functionality and aesthetics have to be preserved, i.e. have to be stable, over the entire life cycle of a
product.
Processed cosmetic products are complex matrixes which undergo spontaneous alterations to reach the
[2]
free energy minimum in accordance with the second thermodynamic law. These so-called intrinsic
[3]
causes may be of physical, physico-chemical or chemical origin. Many reactions and processes may
lead, under the condition of the “market”, to a deviation from the initial, original product properties
at the date of manufacturing. Departure may be caused by thermodynamically driven internal or
[1] [4][5] [6]
externally driven effects, microbiological impact or interactions with packaging and may
finally lead to a loss of specified product functionality or/and aesthetic attributes. This impacts
usability, shelf life and marketability. Destabilization processes of the original product may also be
provoked, enhanced or magnified due to extrinsic (external) factors. For example, state changes may
be triggered by thermal energy loss or gain, light and UV irradiation, mechanical energy input (such
as vibration or pressure), oxygen uptake, humidity, interaction by or with container/closure system
[3]
(packaging), and proliferation of microorganisms.
Cosmetics are of different natures and some consist of several phases, dispersed ones and a continuous
one, and may be classified as suspensions or emulsions. Suspensions are solid particles dispersed in a
liquid phase. Emulsions are composed of two liquid phases, typically oil-in-water (o/w) or water-in-oil
(w/o). Cosmetic dispersions are usually very complex and may contain several phases.
A stability test aims at providing information on the state/behaviour of the cosmetic products in
the container/enclosure under the different conditions to which they may be subjected from their
[7][8][9]
manufacturing date until the end of their recommended period of use. The state of a cosmetic
product and its stability depend upon numerous interrelated physical, physico-chemical and chemical
parameters as well as interaction with environment, and its nature is therefore very complex. In
general, they may be roughly classified as mechanical-driven, thermal- or diffusion-driven, interaction-
[1][7][10][11]
force- driven or externally provoked processes. There is no universal method or technique to
quantify all stability aspects due to the complexity of different pathways of destabilization. Therefore,
it is always necessary to specify precise stability metrics and acceptance criteria.
After determination of the stability metric(s), it is necessary to select appropriate stability test methods
to monitor the alteration of the product over time. It is recommended to select methods that do not
require sample preparation (e.g. dilution) and quantify kinetics of the product destabilization based
[1]
on defined metric(s) in a direct way. Real time measurements can be made by traditional visual
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observations, sensory techniques or use of different measuring techniques which are advantageous
[1]
in being quantitative, objective, traceable, reproducible and retrievable. Scanning and spatially
resolving techniques are appropriate in particular to detect phase separation and help to discriminate
[1][7][10][11]
between phase separation and phase changes.
In the case of very stable products, analytical techniques having high resolution/sensitivity should be
used and procedures can be required in order to accelerate the alteration to shorten the detection time
[1][11]
to meet the predefined stability criteria. Typical acceleration approaches are mechanical ones
(e.g. high gravity by centrifugation) or elevated storage temperatures for a given time. Preservation
[3]
efficacy testing (challenge-test) aims to test microbiological attributes under accelerated conditions.
[5]
However, because of the interrelated physical, physico-chemical and chemical properties of cosmetic
emulsions or suspensions, adequate acceleration methods may be chosen and verified in the context of
[1][11]
a specific product.
Beside direct methods, correlative test methods are utilized focusing on determination of a single
[1]
parameter of the state of a product that is known to correlate with product stability. Typical
parameters measured and compared with pre-defined acceptable values are, for example, mean
particle/droplet size or zeta-potential. These quantities reflect the state at the time of the measurement
and do not yield kinetic information. Such test procedures may be used for quality assessment of a
specified product but, due to the complexity of the state of cosmetic products, currently no theoretical
basis exists to predict the time course of any product alteration based on a single parameter obtained
at any single time point. In addition, most of these measuring techniques demand sample preparation
[1]
and often product dilution.
Due to the cosmetic product formulation’s complexity overall, caution should be employed in stability
assessment and predicting its shelf life, and the properties of the constituents should be considered and
[11]
understood, as well as the product’s behaviour and the factors which influence it.
5 Aspects to be addressed during stability testing
5.1 General
The key aspects to consider when assessing the stability of cosmetics products are listed in 5.2 to 5.6.
Guidance is provided based on the review of relevant sources cited in the text.
5.2 Stage/scale of tested batches
When working on a brand new product (new formula, new manufacturing process, new packaging) and
therefore where no significant body of knowledge is available, it might be appropriate to carry multiple
independent stability studies, usually referred as “preliminary tests”. It is up to the manufacturer to
decide on the number of batches, the scale of their manufacture that are subject to stability testing and
[7][12][9][13]
at what stage of the project development cycle this takes place.
The stability of the final product (final formula, final manufacturing process, final packaging) may be
demonstrated before its commercialization. Accelerated stability evaluation may be conducted prior to
commercialization to predict product shelf life. Following commercialization, the shelf life confirmation
is obtained by long term stability testing on representative formulations.
Minor variations between products subjected to stability testing versus final commercial product can
be acceptable if they are deemed as not having an impact on product characteristics and integrity, but
[9]
need to be documented and justified.
Common acceptable practices include but are not limited to
— usage of formulation samples from the development stage for preliminary tests,
— usage of pilot batches instead of production scale, for some specific non-scale up products and where
[13][14]
the manufacturing process is considered equivalent, and
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— usage of unlabelled packaging, or packaging of different shape, when packaging size, closure system
and material remain unchanged, or when decorative material remains of same nature but with
different design (e.g. same ink versus different print).
[14]
Additionally, matrixing and bracketing are acceptable practices but should be documented and
justified to ensure that the stability study protocol will cover the entire product portfolio and provide
[13][14][15]
enough information (e.g. multiple shade, packaging size).
5.3 Test procedures and conditions
5.3.1 Principle
The general objective of a stability test is to determine whether a given product, in the container in
which it is being marketed, has an adequate shelf life, under the conditions of the market in which it is
[16]
being sold.
Stability testing may be of sufficient duration to cover storage, shipment and subsequent use, and to
guarantee safety and quality.
Manufacturers may, for each formula type, select the pertinent test criteria according to their experience
and evaluate these test criteria at one or more temperatures.
Because of the wide variety of cosmetic products and their inherent complexity, standard stability tests
[7]
cannot always be prescribed. Both real time and accelerated test procedures are used to provide
the desired information. Most cosmetics, due to their short development cycles, require accelerated
test protocols to help predict stability parameters in a shorter period of time. To achieve these end
points, some samples are kept under test conditions designed to accelerate changes that may occur and
some are stored at normal conditions. Test conditions refer to the various manufacturing or storage
[10]
conditions (e.g. batch) or combination of conditions (e.g. container closures) to be studied. The
recommended shelf life may be estimated by accelerated stability tests and can be confirmed by real
[13]
time (long term stability) tests.
While shelf life is determined by the stability of the product, the overall stability profile is made up of
several components, such as
— the inherent chemical and physical stability of the product, and
— the possible interactions between the product (contents) and its primary packaging.
In order to generate the desired information recommended, standard/long term and accelerated test
parameters are outlined in 5.3.2 to 5.3.6.
5.3.2 Temperature and humidity
NOTE See References [10] and [16].
Accelerated and long term conditions can be used. The long term condition is conducted at regular
storage conditions (e.g. controlled room temperature), while the accelerated testing is conducted under
stress conditions (e.g. elevated temperature) which aims to increase the rate of potential degradation.
[3][7][8][9][10][12][13][16]
Throughout this document it is assumed that all temperature and humidity storage conditions might
experience a variation, for example ±3 °C and ±5 % RH.
Accelerated test conditions may vary and should be established based on correlations to real time
storage conditions for the specific region or market. References to commonly used accelerated test
conditions for testing cosmetic products are provided in the Bibliography. The temperature used and
[3][7][10][13][16][17][18][19]
the duration will depend on the product type.
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Samples stored at elevated temperatures represent a more constant degree of acceleration and
render stability predictions as being more accurate. Cosmetic stability guidelines list various storage
[3][16][17][19]
conditions and durations for accelerated stability testing:
— (30 ± 2) °C;
— (37 ± 2) °C;
— (40 ± 2) °C;
— (45 ± 2) °C;
— (50 ± 2) °C.
[16]
Durations range from one week to three months. Relative humidity may be ambient or controlled,
[9][17]
such as 37 °C to 40 °C/75 % to 80 % RH.
Alternative temperature and humidity conditions may be used, including an intermediate condition of
[9][14][20]
(30 ± 2) °C and 65 % RH. Test conditions and durations may be adjusted where justified to
[9][18]
cover the product’s distribution and storage conditions.
Instability can be caused by either chemical reactions or physical processes and often a combination of
both. These alterations proceed at a faster rate at higher temperatures but the degree of acceleration
is variable as it depends on the specific rate constants, which are often unknown. Care should be taken
in the interpretation of results when using temperatures far removed from ambient, as the observed
changes may never occur at normal in market temperatures. Use of moderate elevated temperature, e.g.
[10][17]
37 °C to 40 °C, is a more realistic condition for predicting in market stability.
Tests at low or elevated relative humidity are normally tests of the package and not of the product.
They serve either to show the effect of storage at varying humidity on the container or as a measure of
the barrier properties of the container. Products may be adversely affected by atmospheric humidity
but if this happens in the product in its sale package it indicates that the package provides inadequate
protection from the atmosphere.
Tests at elevated humidity are less likely to accelerate changes at normal storage conditions compared
to tests at elevated temperatures and ambient humidity. If absorption of water vapour presents a risk to
the packaged product’s properties, then testing at elevated humidity may accelerate changes. If the risk
is loss of water or other volatile constituents (such as in permeable packaging), then elevated humidity
may actually retard changes, and testing at low humidity may be more appropriate.
It may be appropriate to consider low temperature storage during stability testing.
— Refrigeration at 5 °C (2 °C to 8 °C) / ambient humidity: This condition may be used to store samples
[3]
to be used as reference samples.
— Freezer at −5 °C to −10 °C: This condition may be used to determine the effects of extreme low
[3]
temperature, for example during transportation.
5.3.3 Cycling of temperature and/or humidity
Tests in which the temperature and/or humidity are changed at regular intervals, and which subject
the package to variations other than static stresses, are sometimes more severe tests than continuous
storage at one condition. These tests provide evidence of emulsion stability, tendency to crystallization,
deposition or clouding, and whether the reaction is reversible. This data are also applicable to
determining how robust a product is to extreme fluctuations in temperature during distribution and
[3][10][16][19]
storage.
Freeze/thaw tests are applicable to
— liquid products as a measure of the potential to develop crystallization or cloud formation, and
— emulsions or creams as an indicator of emulsions stability.
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ISO/TR 18811:2018(E)
Freeze/thaw tests may be carried out on all solutions, emulsions, creams and all other liq
...
RAPPORT ISO/TR
TECHNIQUE 18811
Première édition
2018-02
Cosmétiques — Lignes directrices
relatives aux essais de stabilité des
produits cosmétiques
Cosmetics — Guidelines on the stability testing of cosmetic products
Numéro de référence
ISO/TR 18811:2018(F)
©
ISO 2018
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ISO/TR 18811:2018(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2018
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en oeuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
Publié en Suisse
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ISO/TR 18811:2018(F)
Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principes de base de la stabilité cosmétique . 2
5 Aspects à prendre en compte au cours des essais de stabilité . 3
5.1 Généralités . 3
5.2 Étape/taille des lots soumis à essai . 3
5.3 Modes opératoires d’essai et conditions . 4
5.3.1 Principe . 4
5.3.2 Température et humidité . 5
5.3.3 Cycle de température et/ou d’humidité . . 6
5.3.4 Vibration . 6
5.3.5 Centrifugation . 7
5.3.6 Exposition à la lumière (photosensibilité) . 7
5.4 Altérations physiques, physico-chimiques et chimiques . 8
5.4.1 Phénomènes de déstabilisation physique de différents types de produits . 8
5.4.2 Processus de déstabilisation chimique . 9
5.4.3 Phénomènes de déstabilisation .10
5.4.4 Méthodes d’essai spécifiques .11
5.5 Aspects microbiologiques .13
5.5.1 Généralités .13
5.5.2 Paramètres microbiologiques .13
5.5.3 Conditions d’essai .14
5.5.4 Spécifications microbiologiques .14
5.5.5 Interprétation des résultats .14
5.6 Interaction avec l’emballage .15
5.6.1 Informations générales .15
5.6.2 Types de matériaux d’emballage et principales évaluations possibles .15
5.6.3 Récipients sous pression (aérosols) .15
6 Conclusions de l’essai de stabilité .15
6.1 Évaluation .15
6.2 Rapport .16
Bibliographie .17
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ISO/TR 18811:2018(F)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes
nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est
en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.
L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de
brevets reçues par l'ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir le lien suivant: www .iso .org/ avant -propos.
Le présent document a été élaboré par le comité technique ISO/TC 217, Cosmétiques.
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ISO/TR 18811:2018(F)
Introduction
Les études de stabilité sont destinées à évaluer la capacité d’un produit à conserver ses propriétés
physiques, chimiques et microbiologiques, ainsi que sa fonctionnalité et ses propriétés sensorielles
souhaitées lorsqu’il est stocké et utilisé dans des conditions appropriées par le consommateur. Plus
simplement, l’objectif d’une étude de stabilité est de déterminer la durée de conservation d’un produit
et d’évaluer si un produit contenu dans son emballage est stable lorsqu’il est soumis aux conditions
de commercialisation dans lesquelles il est vendu et utilisé. Les « conditions de commercialisation »
comprennent la distribution (le transport), le stockage en entrepôt et les conditions d’utilisation.
Par conséquent, l’étude de stabilité peut être considérée comme indispensable pour garantir la qualité
du produit. Des essais de stabilité sur les produits cosmétiques sont requis pour:
— obtenir des recommandations relatives à la formulation du produit et au matériau d’emballage
approprié;
— optimiser la formulation et le processus de fabrication;
— déterminer les conditions de transport, de stockage, de mise en rayon et d’utilisation;
— estimer et confirmer la durée de conservation;
— assurer la sécurité de l’utilisateur.
Le présent document identifie des références facilement accessibles pour évaluer la stabilité des
produits cosmétiques sur le marché. Son objectif est de fournir une ressource pour la sélection des essais
de stabilité appropriés. Bien que les présentes lignes directrices offrent un bon point de départ pour
évaluer les nouveaux produits et technologies, une adaptation des essais peut encore être nécessaire
pour tenir compte des différences entre les types de produits et leurs formulations.
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RAPPORT TECHNIQUE ISO/TR 18811:2018(F)
Cosmétiques — Lignes directrices relatives aux essais de
stabilité des produits cosmétiques
1 Domaine d’application
Le présent document fournit des lignes directrices pour les essais de stabilité des produits cosmétiques.
Il examine des références bibliographiques facilement accessibles qui offrent une ressource pour
l’évaluation de la stabilité des produits cosmétiques. Cette revue des lignes directrices disponibles qui
évaluent la stabilité des produits cosmétiques peut être utilisée comme cadre technique/scientifique
afin d’identifier les méthodes les plus appropriées pour l’évaluation de la stabilité des produits
cosmétiques.
Le présent document n’est pas destiné à spécifier les conditions, les paramètres ou les critères des
essais de stabilité.
Compte tenu de la grande diversité des produits cosmétiques, des conditions de stockage et d’utilisation,
il est impossible de définir un moyen unique d’évaluer la stabilité des produits. Par conséquent,
il appartient au fabricant de spécifier et de justifier le protocole de stabilité régissant les méthodes
d’essai, leurs spécifications et les conditions dans lesquelles les produits seront soumis à essais.
2 Références normatives
Le présent document ne contient aucune référence normative.
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions suivants s’appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/
— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp
3.1
évaluation de la stabilité accélérée
étude qui accélère les processus de déstabilisation naturels sous l’effet de facteurs intrinsèques ou
extrinsèques et qui permet de prédire le comportement à long terme
Note 1 à l'article: En règle générale, des modes opératoires physico-chimiques, mécaniques ou thermiques sont
utilisés.
3.2
évaluation de la stabilité en temps réel
étude qui surveille l’état d’un produit afin de déterminer l’évolution temporelle de toute altération de ce
dernier dans des conditions raisonnablement prévisibles de stockage et d’utilisation
Note 1 à l'article: Souvent appelée « essai à long terme » ou « essai de stabilité normalisé ».
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3.3
stabilité
capacité d’un produit cosmétique à résister aux changements ou variations de ses propriétés initiales au
fil du temps dans des conditions déclarées ou raisonnablement prévisibles de stockage et d’utilisation
Note 1 à l'article: Voir Référence [1].
3.4
critères de stabilité
écarts par rapport aux propriétés initiales ou comportement au stade de la production considérés
comme acceptables
Note 1 à l'article: Voir Référence [1].
3.5
paramètres de mesure de la stabilité
propriétés/paramètres de l’état ou du comportement d’un produit cosmétique qu’il convient de
surveiller conformément aux qualités spécifiques exigées pour le produit
Note 1 à l'article: Voir Référence [1].
3.6
durée de conservation
période recommandée durant laquelle un produit cosmétique peut être conservé après sa production
et pendant laquelle la qualité définie du produit reste acceptable dans les conditions prévues de
distribution, de stockage, de mise en rayon et d’utilisation
Note 1 à l'article: Voir Référence [1].
4 Principes de base de la stabilité cosmétique
La conception, la formulation et le processus de fabrication des produits cosmétiques doivent satisfaire
à des demandes et exigences générales et spécifiques de voies de distribution, et plus particulièrement
d’utilisateurs. Les spécifications, la fonctionnalité et l’esthétique doivent être préservées, c’est-à-dire
être stables tout au long du cycle de vie d’un produit.
Les produits cosmétiques manufacturés sont des matrices complexes qui subissent des altérations
spontanées pour atteindre le minimum d’énergie libre conformément à la deuxième loi de la
[2]
thermodynamique . Ces « causes intrinsèques » peuvent être d’origine physique, physico-chimique
[3]
ou chimique . De nombreux processus et réactions peuvent conduire, dans les « conditions de
commercialisation », à un écart par rapport aux propriétés initiales du produit cosmétique au
moment de sa fabrication. Cet écart peut être causé par des effets thermodynamiques internes ou
[1] [4][5] [6]
externes , un impact microbiologique ou des interactions avec l’emballage et peut, à terme,
conduire à une perte de la fonctionnalité spécifiée du produit et/ou de ses attributs esthétiques. Cela
influe sur l’aptitude à l’utilisation, la durée de conservation et la mise sur le marché. Les processus
de déstabilisation du produit original peuvent également être induits, renforcés ou amplifiés par des
facteurs extrinsèques (externes). Par exemple, des changements d’état peuvent être déclenchés par une
perte ou un gain d’énergie thermique, la lumière et le rayonnement UV, un apport en énergie mécanique
(tel qu’une vibration ou une pression), une consommation d’oxygène, l’humidité, une interaction avec
[3]
un contenant/système de fermeture (emballage), et la prolifération de micro-organismes .
Les cosmétiques sont de différentes natures; certains sont constitués de plusieurs phases, des
phases dispersées et une phase continue, et peuvent être classés comme suspensions ou émulsions.
Les suspensions sont des particules solides dispersées dans une phase liquide. Les émulsions sont
composées de deux phases liquides, habituellement huile dans l’eau (H/E) ou eau dans l’huile (E/H). Les
dispersions cosmétiques sont généralement très complexes et peuvent contenir plusieurs phases.
Un essai de stabilité vise à fournir des informations sur l’état/le comportement des produits cosmétiques
dans un contenant/emballage dans les différentes conditions auxquelles ils peuvent être soumis à
[7][8][9]
compter de leur date de fabrication jusqu’à la fin de leur période d’utilisation recommandée . L’état
2 © ISO 2018 – Tous droits réservés
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d’un produit cosmétique et de sa stabilité dépend de nombreux paramètres physiques, physico-chimiques
et chimiques interdépendants, ainsi que de l’interaction avec l’environnement; par conséquent, sa
nature se révèle d’une grande complexité. En général, ils peuvent être globalement classés en processus
[1][7][10][11]
mécaniques, thermiques, de diffusion, induits par une force d’interaction ou externes . Il
n’existe aucune méthode ou technique universelle pour quantifier tous les aspects de la stabilité en
raison de la complexité des différents modes de déstabilisation. Par conséquent, il est toujours nécessaire
de spécifier des paramètres de mesure de la stabilité et des critères d’acceptation précis.
Après détermination du ou des paramètres de mesure de la stabilité, il est nécessaire de sélectionner
des méthodes d’essai de stabilité appropriées pour surveiller l’altération du produit au fil du temps. Il
est recommandé de sélectionner des méthodes qui ne requièrent pas de préparation d’échantillons (par
exemple, dilution) et qui quantifient la cinétique de la déstabilisation du produit d’une manière directe
[1]
en s’appuyant sur un ou plusieurs paramètres de mesure . Des mesurages en temps réel peuvent être
réalisés à l’aide d’observations visuelles classiques, de techniques sensorielles ou en utilisant différentes
techniques de mesure qui présentent des avantages de par leur caractère quantitatif, objectif, traçable,
[1]
reproductible et accessible . Les techniques de scannerisation et de résolution spatiale sont notamment
appropriées pour détecter la séparation de phases et aider à faire la distinction entre séparation de
[1][7][10][11]
phases et changements de phase .
Dans le cas de produits très stables, il convient d’utiliser des techniques analytiques présentant une
haute résolution/sensibilité et des modes opératoires peuvent être requis pour accélérer l’altération
[1]
dans le but de réduire le temps de détection et de répondre ainsi aux critères de stabilité prédéfinis
[11]
. Les approches d’accélération typiques sont des approches mécaniques (par exemple, haute
gravité par centrifugation) ou des températures de stockage élevées pendant un temps donné.
L’essai d’efficacité de conservation (challenge test) est destiné à soumettre à essai les propriétés
[3][5]
microbiologiques dans des conditions accélérées . Cependant, en raison de l’interdépendance des
propriétés physiques, physico-chimiques et chimiques des émulsions ou suspensions cosmétiques, des
méthodes d’accélération appropriées peuvent être sélectionnées et vérifiées dans le cadre d’essai d’un
[1][11]
produit spécifique .
Outre les méthodes directes, des méthodes d’essai corrélatives sont utilisées, lesquelles se concentrent
sur la détermination d’un paramètre unique de l’état d’un produit qui est connu pour être en corrélation
[1]
avec la stabilité du produit . La taille moyenne des particules/gouttelettes ou le potentiel zêta sont
des exemples de paramètres typiques mesurés et comparés à des valeurs acceptables prédéfinies.
Ces quantités représentent l’état au moment du mesurage et ne donnent aucune information d’ordre
cinétique. Ces modes opératoires d’essai peuvent être utilisés pour l’évaluation de la qualité d’un
produit spécifié, mais, en raison de la complexité de l’état des produits cosmétiques, aucune base
théorique n’existe à l’heure actuelle pour prédire l’évolution temporelle de toute altération d’un produit
en s’appuyant sur un paramètre unique obtenu à un moment donné quelconque. En outre, la plupart de
[1]
ces techniques de mesure exigent la préparation d’échantillons et, souvent, la dilution de produits .
En raison de la complexité globale de la formulation du produit cosmétique, il convient de faire preuve
de prudence lors de l’évaluation de la stabilité et de la prédiction de sa durée de conservation, et il
convient que les propriétés des constituants soient prises en compte et comprises, de même que le
[11]
comportement du produit et les facteurs qui l’influencent .
5 Aspects à prendre en compte au cours des essais de stabilité
5.1 Généralités
Les principaux aspects à prendre en compte lors de l’évaluation de la stabilité des produits cosmétiques
sont énumérés de 5.2 à 5.6. Des recommandations sont fournies sur la base de l’étude des sources
pertinentes citées dans le texte.
5.2 Étape/taille des lots soumis à essai
En travaillant sur un nouveau produit d’une marque (nouvelle formule, nouveau processus de
fabrication, nouvel emballage) pour lequel aucun ensemble de connaissances substantiel n’est donc
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ISO/TR 18811:2018(F)
disponible, il peut être approprié de réaliser plusieurs études de stabilité indépendantes, généralement
appelées « essais préliminaires ». Il appartient au fabricant de décider du nombre de lots, du volume
de leur production à soumettre aux essais de stabilité et à quelle étape du cycle de développement du
[7][12][9][13]
projet ceux-ci sont réalisés .
La stabilité du produit final (formule finale, processus de fabrication final, emballage final) peut être
démontrée avant sa commercialisation. Une évaluation de la stabilité accélérée peut être réalisée avant
la commercialisation afin de prédire la durée de conservation du produit. Suite à la commercialisation,
la confirmation de la durée de conservation est obtenue par des essais de stabilité à long terme sur des
formulations représentatives.
Des variations mineures entre les produits soumis aux essais de stabilité et le produit commercialisé
peuvent être acceptables s’il est considéré qu’elles n’ont pas d’impact négatif sur les caractéristiques et
[9]
l’intégrité du produit, mais il est nécessaire que cela soit documenté et justifié .
Les pratiques courantes acceptables comprennent, sans toutefois s’y limiter:
— l’utilisation d’échantillons de formulation dès l’étape de développement pour les essais préliminaires;
— l’utilisation de lots de taille pilote au lieu d’échelle de production pour certains produits spécifiques
ne pouvant pas être mis à l’échelle et pour lesquels le processus de fabrication est considéré comme
[13][14]
équivalent ;
— l’utilisation d’un emballage non étiqueté ou d’un emballage de forme différente, lorsque la taille
de l’emballage, le système de fermeture et le matériau restent inchangés ou lorsque le matériau
décoratif reste de la même nature, mais avec une conception différente (par exemple, même encre,
mais avec une impression différente).
[14]
Les méthodes des extrêmes et de la matrice sont également des pratiques acceptables, mais
il convient de les documenter et de les justifier afin de garantir que le protocole d’étude de stabilité
couvrira l’ensemble du portefeuille de produit et fournira suffisamment d’informations (par exemple,
[13][14][15]
teintes multiples, taille de l’emballage) .
5.3 Modes opératoires d’essai et conditions
5.3.1 Principe
L’objectif général d’un essai de stabilité est de déterminer si un produit donné, dans le contenant dans
lequel il est commercialisé, présente une durée de conservation appropriée dans les conditions de
[16]
commercialisation dans lesquelles il est vendu .
Les essais de stabilité peuvent être d’une durée suffisante pour couvrir le stockage, le transport et
l’utilisation ultérieure, ainsi que pour garantir la sécurité et la qualité.
Pour chaque type de formule, les fabricants peuvent sélectionner les critères d’essai pertinents en
fonction de leur expérience et évaluer ces critères à une ou plusieurs températures.
En raison de la grande diversité des produits cosmétiques et de leur complexité intrinsèque, des essais
[7]
de stabilité normalisés ne peuvent pas toujours être prescrits . Des modes opératoires d’essai en
temps réel et accélérés sont utilisés pour obtenir les informations désirées. Du fait de leurs cycles de
développement courts, la plupart des cosmétiques requièrent des protocoles d’essai accélérés pour
permettre de prédire les paramètres de stabilité dans un délai plus bref. Pour atteindre ces critères
d’évaluation, certains échantillons sont maintenus dans des conditions d’essai conçues pour accélérer
les changements qui peuvent se produire et certains sont conservés dans des conditions normales. Les
conditions d’essai renvoient aux différentes conditions de fabrication ou de stockage (lot par exemple)
[10]
ou à la combinaison de conditions (par exemple, fermetures de contenant) à étudier . La durée
de conservation recommandée peut être estimée à l’aide d’essais de stabilité accélérés et peut être
[13]
confirmée par des essais en temps réel (de stabilité à long terme) .
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Tandis que la durée de conservation est déterminée par la stabilité du produit, le profil de stabilité
global est constitué de plusieurs composants, tels que:
— la stabilité chimique et physique inhérente au produit; et
— les possibles interactions entre le produit (contenu) et son emballage primaire.
Afin d’obtenir les informations souhaitées telles qu’elles sont recommandées, des paramètres d’essai
normalisés/à long terme et accélérés sont exposés de 5.3.2 à 5.3.6.
5.3.2 Température et humidité
NOTE Voir Références [10] et [16].
Des conditions accélérées et à long terme peuvent être utilisées. La condition à long terme est réalisée
dans des conditions de stockage normales (par exemple, température ambiante contrôlée), tandis que
les essais accélérés sont réalisés dans des conditions de contrainte (par exemple, température ambiante
[3][7][8][9][10][12][13][16]
élevée), avec l’objectif d’augmenter la vitesse de dégradation potentielle .
Dans le présent document, il est supposé que toutes les conditions de température et d’humidité de
stockage peuvent subir une variation, par exemple de ±3 °C et ±5 % HR.
Les conditions d’essai accélérées peuvent varier et il convient de les établir en s’appuyant sur des
corrélations avec les conditions de stockage en temps réel pour la région ou le marché spécifique. Des
références aux conditions d’essai accélérées couramment utilisées pour soumettre à essai les produits
cosmétiques sont disponibles dans la Bibliographie. La température utilisée et la durée dépendront du
[3][7][10][13][16][17][18][19]
type de produit .
Les échantillons conservés à des températures élevées représentent un degré d’accélération plus
constant et rendent les prédictions de stabilité plus précises. Les lignes directrices relatives à la
stabilité des cosmétiques énumèrent différentes conditions de stockage et durées pour les essais de
[3][16][17][19]
stabilité accélérés :
— (30 ± 2) °C;
— (37 ± 2) °C;
— (40 ± 2) °C;
— (45 ± 2) °C;
— (50 ± 2) °C.
[16]
Les durées varient d’une semaine à trois mois. L’humidité relative peut être ambiante ou contrôlée,
[9][17]
telle que 37 °C à 40 °C / 75 % à 80 % HR .
Des conditions alternatives de température et d’humidité peuvent être utilisées, y compris une
[9][14][20]
condition intermédiaire de (30 ± 2) °C et 65 % HR . Les conditions d’essai et les durées peuvent
être ajustées lorsque cela se justifie pour couvrir les conditions de distribution et de stockage du
[9][18]
produit .
Une instabilité peut être causée soit par des réactions chimiques, soit par des processus physiques,
et souvent par une combinaison des deux. Ces altérations se produisent plus rapidement et à des
températures plus élevées, mais le degré d’accélération est variable, car celui-ci dépend des constantes
de vitesse spécifiques, qui sont souvent inconnues. Il convient d’accorder une attention particulière
à l’interprétation des résultats en cas d’utilisation de températures très éloignées de l
...
SLOVENSKI STANDARD
oSIST-TP ISO/TR 18811:2018
01-november-2018
.R]PHWLND6PHUQLFH]DSUHVNXãDQMHVWDELOQRVWLNR]PHWLþQLKL]GHONRY
Cosmetics - Guidelines on the stability testing of cosmetic products
Cosmétiques - Lignes directrices relatives aux essais de stabilité des produits
cosmétiques
Ta slovenski standard je istoveten z: ISO/TR 18811:2018
ICS:
71.100.70 .R]PHWLND7RDOHWQL Cosmetics. Toiletries
SULSRPRþNL
oSIST-TP ISO/TR 18811:2018 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST-TP ISO/TR 18811:2018
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oSIST-TP ISO/TR 18811:2018
TECHNICAL ISO/TR
REPORT 18811
First edition
2018-02
Cosmetics — Guidelines on the
stability testing of cosmetic products
Cosmétiques — Lignes directrices relatives aux essais de stabilité des
produits cosmétiques
Reference number
ISO/TR 18811:2018(E)
©
ISO 2018
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oSIST-TP ISO/TR 18811:2018
ISO/TR 18811:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
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oSIST-TP ISO/TR 18811:2018
ISO/TR 18811:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic principles of cosmetic stability . 2
5 Aspects to be addressed during stability testing . 3
5.1 General . 3
5.2 Stage/scale of tested batches . 3
5.3 Test procedures and conditions . 4
5.3.1 Principle . 4
5.3.2 Temperature and humidity . 4
5.3.3 Cycling of temperature and/or humidity . 5
5.3.4 Vibration . 6
5.3.5 Centrifugation . 6
5.3.6 Exposure to light (photostability) . 6
5.4 Physical, physico-chemical and chemical alterations . 7
5.4.1 Physical destabilization phenomena of different product types . 7
5.4.2 Chemical destabilization processes . 8
5.4.3 Destabilization phenomena . 9
5.4.4 Specific test methods .10
5.5 Microbiological aspects .12
5.5.1 General.12
5.5.2 Microbiological parameters .12
5.5.3 Testing conditions .12
5.5.4 Microbiological specifications .13
5.5.5 Interpretation of results .13
5.6 Interaction with packaging .13
5.6.1 General information .13
5.6.2 Types of packing materials and main possible evaluations .13
5.6.3 Pressure vessels (aerosols) .14
6 Stability test conclusions .14
6.1 Evaluation .14
6.2 Report .14
Bibliography .15
© ISO 2018 – All rights reserved iii
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oSIST-TP ISO/TR 18811:2018
ISO/TR 18811:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 217, Cosmetics.
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Introduction
Stability studies are aimed at assessing the ability of a product to maintain the desired physical,
chemical and microbiological properties, as well as functionality and sensorial properties when stored
and used under appropriate conditions by the consumer. More simply, the objective of a stability study is
to determine the shelf life of a product and to evaluate whether a product in the package is stable when
subjected to the market conditions in which it is sold and used. The “market conditions” encompass
distribution (transportation), warehouse storage and conditions during use.
Thus, the stability study may be seen as a prerequisite for ensuring product quality. Stability tests on
cosmetic products are required for
— obtaining a guidance on the formulation of the product, and the appropriate packaging material,
— optimizing the formulation and manufacturing process,
— determining conditions of transportation, storage, display and manner of use,
— estimating and confirming shelf life, and
— ensuring customer safety.
This document identifies readily available references to assess the stability of cosmetic products on the
market. Its purpose is to provide a resource for the selection of the appropriate stability tests. Although
these guidelines provide a helpful starting point to evaluate new products and technologies, adapting
the testing to reflect differences between product types and formulations may still be necessary.
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oSIST-TP ISO/TR 18811:2018
TECHNICAL REPORT ISO/TR 18811:2018(E)
Cosmetics — Guidelines on the stability testing of cosmetic
products
1 Scope
This document gives guidelines for the stability testing of cosmetic products. It reviews readily
available bibliographic references that provide a resource for the assessment of the stability of cosmetic
products. This review of the available guidelines that assess the stability of cosmetic products can
serve as a technical/scientific framework to identify the most suitable methods for the assessment of
the stability of cosmetic products.
This document does not aim to specify the conditions, parameters or criteria of stability testing.
Considering the wide variety of cosmetic products, storage and use conditions, it is not possible to
define a single way to assess product stability. Therefore, it is up to the manufacturer to specify and
justify the stability protocol to cover test methods, specifications and conditions at which products will
be tested.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
accelerated stability evaluation
study designed to speed up naturally occurring destabilization processes due to intrinsic or extrinsic
factors and which predicts the behaviour over the long term
Note 1 to entry: Typically, physico-chemical, mechanical or thermal procedures are employed.
3.2
real time stability evaluation
study that monitors the state of a product to determine the time course of any alteration to it under
reasonably expected conditions of storage and use
Note 1 to entry: Often called “long term test” or “standard stability test”.
3.3
stability
ability of a cosmetic product to resist change or variation of its initial properties over time under stated
or reasonably foreseeable conditions of storage and use
Note 1 to entry: See Reference [1].
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3.4
stability criteria
deviations from initial properties or behaviour at production state, which are acceptable
Note 1 to entry: See Reference [1].
3.5
stability metrics
properties/parameters of the state or behaviour of a cosmetic product which should be monitored
according to demanded, specific product qualities
Note 1 to entry: See Reference [1].
3.6
shelf life
recommended time period that a cosmetic product can be kept after its production, during which the
defined quality of the product remains acceptable under expected conditions of distribution, storage,
display and usage
Note 1 to entry: See Reference [1].
4 Basic principles of cosmetic stability
Design, formulation and the manufacturing process of cosmetic products have to fulfil general and
specific demands and requirements of distribution pathways, and especially of customers. Specification,
functionality and aesthetics have to be preserved, i.e. have to be stable, over the entire life cycle of a
product.
Processed cosmetic products are complex matrixes which undergo spontaneous alterations to reach the
[2]
free energy minimum in accordance with the second thermodynamic law. These so-called intrinsic
[3]
causes may be of physical, physico-chemical or chemical origin. Many reactions and processes may
lead, under the condition of the “market”, to a deviation from the initial, original product properties
at the date of manufacturing. Departure may be caused by thermodynamically driven internal or
[1] [4][5] [6]
externally driven effects, microbiological impact or interactions with packaging and may
finally lead to a loss of specified product functionality or/and aesthetic attributes. This impacts
usability, shelf life and marketability. Destabilization processes of the original product may also be
provoked, enhanced or magnified due to extrinsic (external) factors. For example, state changes may
be triggered by thermal energy loss or gain, light and UV irradiation, mechanical energy input (such
as vibration or pressure), oxygen uptake, humidity, interaction by or with container/closure system
[3]
(packaging), and proliferation of microorganisms.
Cosmetics are of different natures and some consist of several phases, dispersed ones and a continuous
one, and may be classified as suspensions or emulsions. Suspensions are solid particles dispersed in a
liquid phase. Emulsions are composed of two liquid phases, typically oil-in-water (o/w) or water-in-oil
(w/o). Cosmetic dispersions are usually very complex and may contain several phases.
A stability test aims at providing information on the state/behaviour of the cosmetic products in
the container/enclosure under the different conditions to which they may be subjected from their
[7][8][9]
manufacturing date until the end of their recommended period of use. The state of a cosmetic
product and its stability depend upon numerous interrelated physical, physico-chemical and chemical
parameters as well as interaction with environment, and its nature is therefore very complex. In
general, they may be roughly classified as mechanical-driven, thermal- or diffusion-driven, interaction-
[1][7][10][11]
force- driven or externally provoked processes. There is no universal method or technique to
quantify all stability aspects due to the complexity of different pathways of destabilization. Therefore,
it is always necessary to specify precise stability metrics and acceptance criteria.
After determination of the stability metric(s), it is necessary to select appropriate stability test methods
to monitor the alteration of the product over time. It is recommended to select methods that do not
require sample preparation (e.g. dilution) and quantify kinetics of the product destabilization based
[1]
on defined metric(s) in a direct way. Real time measurements can be made by traditional visual
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observations, sensory techniques or use of different measuring techniques which are advantageous
[1]
in being quantitative, objective, traceable, reproducible and retrievable. Scanning and spatially
resolving techniques are appropriate in particular to detect phase separation and help to discriminate
[1][7][10][11]
between phase separation and phase changes.
In the case of very stable products, analytical techniques having high resolution/sensitivity should be
used and procedures can be required in order to accelerate the alteration to shorten the detection time
[1][11]
to meet the predefined stability criteria. Typical acceleration approaches are mechanical ones
(e.g. high gravity by centrifugation) or elevated storage temperatures for a given time. Preservation
[3]
efficacy testing (challenge-test) aims to test microbiological attributes under accelerated conditions.
[5]
However, because of the interrelated physical, physico-chemical and chemical properties of cosmetic
emulsions or suspensions, adequate acceleration methods may be chosen and verified in the context of
[1][11]
a specific product.
Beside direct methods, correlative test methods are utilized focusing on determination of a single
[1]
parameter of the state of a product that is known to correlate with product stability. Typical
parameters measured and compared with pre-defined acceptable values are, for example, mean
particle/droplet size or zeta-potential. These quantities reflect the state at the time of the measurement
and do not yield kinetic information. Such test procedures may be used for quality assessment of a
specified product but, due to the complexity of the state of cosmetic products, currently no theoretical
basis exists to predict the time course of any product alteration based on a single parameter obtained
at any single time point. In addition, most of these measuring techniques demand sample preparation
[1]
and often product dilution.
Due to the cosmetic product formulation’s complexity overall, caution should be employed in stability
assessment and predicting its shelf life, and the properties of the constituents should be considered and
[11]
understood, as well as the product’s behaviour and the factors which influence it.
5 Aspects to be addressed during stability testing
5.1 General
The key aspects to consider when assessing the stability of cosmetics products are listed in 5.2 to 5.6.
Guidance is provided based on the review of relevant sources cited in the text.
5.2 Stage/scale of tested batches
When working on a brand new product (new formula, new manufacturing process, new packaging) and
therefore where no significant body of knowledge is available, it might be appropriate to carry multiple
independent stability studies, usually referred as “preliminary tests”. It is up to the manufacturer to
decide on the number of batches, the scale of their manufacture that are subject to stability testing and
[7][12][9][13]
at what stage of the project development cycle this takes place.
The stability of the final product (final formula, final manufacturing process, final packaging) may be
demonstrated before its commercialization. Accelerated stability evaluation may be conducted prior to
commercialization to predict product shelf life. Following commercialization, the shelf life confirmation
is obtained by long term stability testing on representative formulations.
Minor variations between products subjected to stability testing versus final commercial product can
be acceptable if they are deemed as not having an impact on product characteristics and integrity, but
[9]
need to be documented and justified.
Common acceptable practices include but are not limited to
— usage of formulation samples from the development stage for preliminary tests,
— usage of pilot batches instead of production scale, for some specific non-scale up products and where
[13][14]
the manufacturing process is considered equivalent, and
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— usage of unlabelled packaging, or packaging of different shape, when packaging size, closure system
and material remain unchanged, or when decorative material remains of same nature but with
different design (e.g. same ink versus different print).
[14]
Additionally, matrixing and bracketing are acceptable practices but should be documented and
justified to ensure that the stability study protocol will cover the entire product portfolio and provide
[13][14][15]
enough information (e.g. multiple shade, packaging size).
5.3 Test procedures and conditions
5.3.1 Principle
The general objective of a stability test is to determine whether a given product, in the container in
which it is being marketed, has an adequate shelf life, under the conditions of the market in which it is
[16]
being sold.
Stability testing may be of sufficient duration to cover storage, shipment and subsequent use, and to
guarantee safety and quality.
Manufacturers may, for each formula type, select the pertinent test criteria according to their experience
and evaluate these test criteria at one or more temperatures.
Because of the wide variety of cosmetic products and their inherent complexity, standard stability tests
[7]
cannot always be prescribed. Both real time and accelerated test procedures are used to provide
the desired information. Most cosmetics, due to their short development cycles, require accelerated
test protocols to help predict stability parameters in a shorter period of time. To achieve these end
points, some samples are kept under test conditions designed to accelerate changes that may occur and
some are stored at normal conditions. Test conditions refer to the various manufacturing or storage
[10]
conditions (e.g. batch) or combination of conditions (e.g. container closures) to be studied. The
recommended shelf life may be estimated by accelerated stability tests and can be confirmed by real
[13]
time (long term stability) tests.
While shelf life is determined by the stability of the product, the overall stability profile is made up of
several components, such as
— the inherent chemical and physical stability of the product, and
— the possible interactions between the product (contents) and its primary packaging.
In order to generate the desired information recommended, standard/long term and accelerated test
parameters are outlined in 5.3.2 to 5.3.6.
5.3.2 Temperature and humidity
NOTE See References [10] and [16].
Accelerated and long term conditions can be used. The long term condition is conducted at regular
storage conditions (e.g. controlled room temperature), while the accelerated testing is conducted under
stress conditions (e.g. elevated temperature) which aims to increase the rate of potential degradation.
[3][7][8][9][10][12][13][16]
Throughout this document it is assumed that all temperature and humidity storage conditions might
experience a variation, for example ±3 °C and ±5 % RH.
Accelerated test conditions may vary and should be established based on correlations to real time
storage conditions for the specific region or market. References to commonly used accelerated test
conditions for testing cosmetic products are provided in the Bibliography. The temperature used and
[3][7][10][13][16][17][18][19]
the duration will depend on the product type.
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Samples stored at elevated temperatures represent a more constant degree of acceleration and
render stability predictions as being more accurate. Cosmetic stability guidelines list various storage
[3][16][17][19]
conditions and durations for accelerated stability testing:
— (30 ± 2) °C;
— (37 ± 2) °C;
— (40 ± 2) °C;
— (45 ± 2) °C;
— (50 ± 2) °C.
[16]
Durations range from one week to three months. Relative humidity may be ambient or controlled,
[9][17]
such as 37 °C to 40 °C/75 % to 80 % RH.
Alternative temperature and humidity conditions may be used, including an intermediate condition of
[9][14][20]
(30 ± 2) °C and 65 % RH. Test conditions and durations may be adjusted where justified to
[9][18]
cover the product’s distribution and storage conditions.
Instability can be caused by either chemical reactions or physical processes and often a combination of
both. These alterations proceed at a faster rate at higher temperatures but the degree of acceleration
is variable as it depends on the specific rate constants, which are often unknown. Care should be taken
in the interpretation of results when using temperatures far removed from ambient, as the observed
changes may never occur at normal in market temperatures. Use of moderate elevated temperature, e.g.
[10][17]
37 °C to 40 °C, is a more realistic condition for predicting in market stability.
Tests at low or elevated relative humidity are normally tests of the package and not of the product.
They serve either to show the effect of storage at varying humidity on the container or as a measure of
the barrier properties of the container. Products may be adversely affected by atmospheric humidity
but if this happens in the product in its sale package it indicates that the package provides inadequate
protection from the atmosphere.
Tests at elevated humidity are less likely to accelerate changes at normal storage conditions compared
to tests at elevated temperatures and ambient humidity. If absorption of water vapour presents a risk to
the packaged product’s properties, then testing at elevated humidity may accelerate changes. If the risk
is loss of water or other volatile constituents (such as in permeable packaging), then elevated humidity
may actually retard changes, and testing at low humidity may be more appropriate.
It may be appropriate to consider low temperature storage during stability testing.
— Refrigeration at 5 °C (2 °C to 8 °C) / ambient humidity: This condition may be used to store samples
[3]
to be used as reference samples.
— Freezer at −5 °C to −10 °C: This condition may be used to determine the effects of extreme low
[3]
temperature, for example during transportation.
5.3.3 Cycling of temperature and/or humidity
Tests in which the temperature and/or humidity are changed at regular intervals, and which subject
the package to variations other than static stresses, are sometimes more severe tests than continuous
storage at one condition. These tests provide evidence of emulsion stability, tendency to crystallization,
deposition or clouding, and whether the reaction is reversible. This data are also applicable to
determining how robust a product is to extreme fluctuations in temperature during distribution and
[3][10][16][19]
storage.
Freeze/thaw tests are applicable to
— liquid products as a measure of the potential to develop crystallization or cloud formation, and
— emulsions or creams as an indicator of emulsions stability.
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Freeze/thaw tests may be carried out on all soluti
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