SIST EN ISO 23698:2025
(Main)Cosmetics - Measurement of the sunscreen efficacy by diffuse reflectance spectroscopy (ISO 23698:2024)
Cosmetics - Measurement of the sunscreen efficacy by diffuse reflectance spectroscopy (ISO 23698:2024)
This document provides a procedure to characterize the sun protection factor (SPF), UVA protection factor (UVA-PF) and critical wavelength (CW) protection of sunscreen products without requiring biological responses. The test method is applicable for emulsions and single-phase products. The method has not been evaluated for use with powder forms sunscreen products.
This document gives specifications to enable determination of the absolute spectral absorbance characteristics of a sunscreen product on skin to estimate sunburn and UVA protection. It is applicable to products that contain any component able to absorb, reflect or scatter ultraviolet (UV) rays and which are intended to be placed in contact with human skin.
Kosmetische Mittel - Messung der Sonnenschutzwirkung mittels Diffusreflexionsspektroskopie (ISO 23698:2024)
Dieses Dokument enthält ein Verfahren zur Charakterisierung des Sonnenschutzfaktors (SPF, en: sun protection factor), des UVA-Schutzfaktors (UVA-PF) und des Schutzes bei kritischer Wellenlänge (CW, en: critical wavelength) von Sonnenschutzmitteln, ohne dass biologische Reaktionen erforderlich sind. Das Prüfverfahren ist anwendbar für Emulsionen und einphasige Produkte. Das Verfahren wurde nicht hinsichtlich der Anwendung mit Sonnenschutzmitteln in Puderform beurteilt.
Dieses Dokument enthält Spezifikationen, welche die Bestimmung der absoluten spektralen Extinktionseigenschaften eines Sonnenschutzmittels auf der Haut ermöglichen, um den Sonnenbrand- und UVA-Schutz abzuschätzen. Es ist anwendbar für Erzeugnisse, welche jegliche Komponenten beinhalten, die ultraviolette (UV-)Strahlen absorbieren, reflektieren oder streuen können und dazu bestimmt sind, mit der menschlichen Haut in Kontakt gebracht zu werden.
Cosmétiques - Mesurage de l’efficacité des produits de protection solaire par spectroscopie de réflectance diffuse (ISO 23698:2024)
Le présent document fournit un mode opératoire pour caractériser le facteur de protection solaire (FPS), le facteur de protection UVA (FPUVA) et la longueur d’onde critique (CW) des produits de protection solaire sans nécessiter de réponse biologique. La méthode d’essai est applicable aux produits monophasés et aux émulsions. La méthode n’a pas été évaluée pour une utilisation avec des produits de protection solaire sous forme de poudre.
Le présent document fournit des spécifications pour permettre la détermination des caractéristiques absolues d’absorbance spectrale d’un produit de protection solaire sur la peau et ainsi estimer la protection contre les UVA et les érythèmes solaires. Il peut s’appliquer à des produits qui contiennent tout composant pouvant absorber, refléter ou diffuser les rayons ultraviolets (UV) et qui sont destinés à être mis en contact avec la peau humaine.
Kozmetika - Merjenje učinkovitosti zaščite pred soncem z difuzno refleksijsko spektroskopijo (ISO 23698:2024)
Ta dokument opisuje postopek za določanje lastnosti faktorja zaščite pred soncem (SPF), zaščitnega faktorja UVA (UVA-PF) in zaščite pred kritično valovno dolžino (CW) izdelkov za zaščito pred soncem brez potrebe po biološkem odzivu. Preskusna metoda se uporablja za emulzije in enofazne izdelke. Metoda ni bila ovrednotena za uporabo z izdelki za zaščito pred soncem v prahu.
Ta dokument podaja specifikacije, ki omogočajo določitev lastnosti absolutne spektralne absorpcije izdelka za zaščito pred soncem na koži za ocenjevanje zaščite pred sončnimi opeklinami in žarki UVA. Uporablja se za izdelke, ki vsebujejo katero koli sestavino za vpijanje, odbijanje ali razpršitev ultravijoličnih žarkov in so namenjeni nanosu na človeško kožo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2025
Kozmetika - Merjenje učinkovitosti zaščite pred soncem z difuzno refleksijsko
spektroskopijo (ISO 23698:2024)
Cosmetics - Measurement of the sunscreen efficacy by diffuse reflectance spectroscopy
(ISO 23698:2024)
Kosmetische Mittel - Messung der Sonnenschutzwirkung mittels
Diffusreflexionsspektroskopie (ISO 23698:2024)
Cosmétiques - Mesurage de l’efficacité des produits de protection solaire par
spectroscopie de réflectance diffuse (ISO 23698:2024)
Ta slovenski standard je istoveten z: EN ISO 23698:2025
ICS:
71.100.70 Kozmetika. Toaletni Cosmetics. Toiletries
pripomočki
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 23698
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2025
EUROPÄISCHE NORM
ICS 71.100.70
English Version
Cosmetics - Measurement of the sunscreen efficacy by
diffuse reflectance spectroscopy (ISO 23698:2024)
Cosmétiques - Mesurage de l'efficacité des produits de Kosmetische Mittel - Messung der
protection solaire par spectroscopie de réflectance Sonnenschutzwirkung mittels
diffuse (ISO 23698:2024) Diffusreflexionsspektroskopie (ISO 23698:2024)
This European Standard was approved by CEN on 22 November 2024.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23698:2025 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 23698:2025) has been prepared by Technical Committee ISO/TC 217
"Cosmetics" in collaboration with Technical Committee CEN/TC 392 “Cosmetics” the secretariat of
which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by July 2025, and conflicting national standards shall be
withdrawn at the latest by July 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 23698:2024 has been approved by CEN as EN ISO 23698:2025 without any modification.
International
Standard
ISO 23698
First edition
Cosmetics — Measurement of
2024-12
the sunscreen efficacy by diffuse
reflectance spectroscopy
Cosmétiques — Mesurage de l’efficacité des produits de
protection solaire par spectroscopie de réflectance diffuse
Reference number
ISO 23698:2024(en) © ISO 2024
ISO 23698:2024(en)
© ISO 2024
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
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 23698:2024(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions .1
3.2 Symbols .4
4 Principle . 5
5 Apparatus and test method . 5
5.1 In vitro UV spectrophotometer .5
5.2 In vitro substrate/plate .6
5.3 In vivo diffuse reflectance spectrometers (DRS) specifications .6
5.4 Monitoring the DRS systems .7
5.4.1 Monochromatic system .7
5.4.2 Polychromatic system.7
5.5 Test method .7
5.5.1 General .7
5.5.2 Subject exclusion criteria .7
5.5.3 Skin colour of the test subjects .8
5.5.4 Frequency of participation in tests .8
5.5.5 Number of test subjects.8
5.5.6 Ethics and consent .8
5.5.7 Study preparations .8
5.5.8 Unprotected skin remittance measurement .8
5.5.9 Training for Technician performing sunscreen application .9
5.5.10 Sunscreen application to test subject .9
5.5.11 Protected skin remittance measurements .9
6 In vitro spectrophotometer measurements .11
6.1 General .11
6.2 In vitro measurement preparation. 12
6.2.1 Blank reference PMMA plate . 12
6.2.2 Product application . 12
6.2.3 Product spreading . 12
6.2.4 Spreading for alcoholic products . 12
6.3 In vitro measurement . 13
6.4 Determination of A . 13
vt0
6.5 Determination of the UV exposure dose . 13
6.6 Measurement of in vitro sunscreen-treated plates post-irradiation .14
6.6.1 General .14
6.6.2 Calculation of the A (λ) post irradiated spectrum .14
vt1
6.7 Determination of the hybridization wavelength.14
6.7.1 Monochromatic system .14
6.7.2 Polychromatic system. 15
7 Spectral ratio of photo-degradation (S ) .15
RPD
7.1 General . 15
7.2 Determination of S (λ) . 15
RPD
8 Calculations to estimate SPF and UVA-PF .16
8.1 Determination of A (λ) .16
HDRSi
8.1.1 Determination of A (λ) (monochromatic system) .16
DRSi
8.1.2 Determination of the A (polychromatic system) .16
DRSi
8.1.3 Determination of the individual hybridization scalar value – C .17
Ai
8.1.4 Calculation of final hybrid absorbance spectrum .17
iii
ISO 23698:2024(en)
8.2 Calculate test material SPF .18
HDRSi
8.3 Calculate test material UVA-PF .18
i
8.4 Critical wavelength calculation .18
8.5 Calculation of the mean and standard deviations for SPF and UVA-PF .19
8.6 Statistical criterion . 20
8.7 Reference standards for SPF and UVA-PF . 20
8.7.1 Establishment of SPF and UVA-PF for product claim: . 20
8.7.2 Other calculations . 20
8.8 Data rejection criteria . 20
8.8.1 Subject data rejection criterion . 20
8.8.2 Site-specific data rejection criterion .21
8.9 Test failure criteria .21
9 Test report .21
9.1 General .21
9.2 Data in tabular form for each test subject . 22
Annex A (informative) Test flow chart monochromatic and polychromatic DRS .23
Annex B (normative) Calibration check of UV spectrophotometer and plate transmittance test
(in vitro measurements) .25
Annex C (normative) Calibration of solar simulator irradiance and radiometer procedure .29
Annex D (normative) Test plate and surface specifications.35
Annex E (normative) Computation values — PPD and erythema action spectra and UVA and UV-
SSR spectral irradiances .37
Annex F (normative) Statistics and calculations .40
Annex G (normative) SPF, UVA-PF and CW reference sunscreen formulations .43
Annex H (informative) Definition and examples of valid skin DRS results .44
Annex I (normative) Optical fibres and calibration .46
Annex J (normative) Product application.47
Annex K (normative) ISO 23698 test report .50
Bibliography .52
iv
ISO 23698:2024(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 217, Cosmetics, in collaboration with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 392, Cosmetics, in accordance
with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
ISO 23698:2024(en)
Introduction
Exposure to solar ultraviolet radiation (UVR) is the main environmental source of acute and chronic damage
to human skin. Skin cancer is the most prevalent form of cancer of the body and is primarily driven by
exposure to sunlight. Protection against exposure to solar UVB and UVA radiation is, therefore, an important
public health issue. The use of topically applied sunscreens is a critical part of holistic programs of consumer
UVR protection, including the use of appropriate clothing, hats and minimizing exposure to the sun.
The sun protection factor (SPF) has historically been measured by an in vivo method (see ISO 24444) to
communicate the magnitude of the protection provided by sunscreens from sunburning UVR. Other test
methods have been developed and provided to assess the breadth and magnitude of the protection in the
UVA portion of the sun’s spectrum (see ISO 24442 and ISO 24443).
This test method given in this document is an alternative to ISO 24443 and ISO 24444 methods.
Invasive methods based on tests conducted on human beings are ethically problematic, time-consuming and
very costly. Therefore, it has long been desired to develop alternative methods to assess both the magnitude
and breadth of protection afforded by sunscreens that do not require invasive procedures and that reliably
provide equivalent testing sensitivity and accuracy as the existing invasive in vivo testing methods.
The hybrid diffuse reflectance spectroscopy method described herein, provides a non-invasive optical
assessment of the protection provided by topically applied sunscreen products as measured in situ on human
skin as used by consumers, without requiring physiological responses and causing no physical harm to the
test subject. By combining full spectrum in vitro spectroscopic measurements of the sunscreen, with optical
measurements of the sunscreen transmission in the UVA on human skin, a hybrid spectrum is derived that
provides full assessment of both magnitude and breadth of sunscreen protection in both the UVB and UVA
regions of the sun’s spectrum, correlating closely with in vivo SPF, in vitro UVA-PF and critical wavelength
test results demonstrating equivalence of this test method against ISO 24444 and ISO 24443 methods.
vi
International Standard ISO 23698:2024(en)
Cosmetics — Measurement of the sunscreen efficacy by
diffuse reflectance spectroscopy
1 Scope
This document provides a procedure to characterize the sun protection factor (SPF), UVA protection factor
(UVA-PF) and critical wavelength (CW) protection of sunscreen products without requiring biological
responses. The test method is applicable for emulsions and single-phase products. The method has not been
evaluated for use with powder forms sunscreen products.
This document gives specifications to enable determination of the absolute spectral absorbance
characteristics of a sunscreen product on skin to estimate sunburn and UVA protection. It is applicable to
products that contain any component able to absorb, reflect or scatter ultraviolet (UV) rays and which are
intended to be placed in contact with human skin.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
3.1 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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
absorbance
A
measure of the energy blocked, either by optical absorption or by physical scattering/reflection
3.1.2
absorbance spectrum
A(λ)
sunscreen optical absorbance at wavelength λ
Note 1 to entry: Logarithm to the base 10 of the reciprocal of the spectral transmittance τ(λ). A(λ) = -[log τ(λ)].
3.1.3
absorbance by diffuse reflectance spectroscopy
absorbance by DRS
A (λ)
DRS
absorbance spectrum calculated from DRS as a function of wavelength λ
Note 1 to entry: The absorbance spectrum relevant to this document is 320 nm to 400 nm.
ISO 23698:2024(en)
3.1.4
absorbance after hybridization
A (λ)
HDRS
final absorbance spectrum calculated from the hybridized signals as a function of wavelength λ after
correction for photo-degradation
Note 1 to entry: The final absorbance spectrum is 290 nm to 400 nm
3.1.5
calibration factor
C
cal
correction applied to a measured quantity value to compensate for a known systematic effect
3.1.6
in vitro UV absorbance spectrum pre irradiation
in vitro absorbance before UV exposure (pre irradiation)
A (λ)
vt0
arithmetic mean in vitro absorbance spectrum of a sunscreen product measured before UV exposure
Note 1 to entry: The absorbance spectrum is 290 nm to 400 nm.
3.1.7
in vitro UV absorbance spectrum post irradiation
in vitro absorbance after UV exposure (post irradiation)
A (λ)
vt1
arithmetic mean in vitro absorbance spectrum of a sunscreen product measured after UV exposure
Note 1 to entry: The absorbance spectrum is 290 nm to 400 nm.
3.1.8
hybridization constant
C
Ai
scalar factor to adjust an in vitro spectrum A (λ) at each wavelength to the individual A
vt1 DRSi
3.1.9
critical wavelength
CW
λ
c
wavelength at which the area under the absorbance curve represents 90 % of the total area under the curve
in the UV region
3.1.10
dose
D
UVA radiant exposure dose for pre-irradiation of sunscreen products (1,2 x UVA-PF J/cm )
DRS
3.1.11
wavelength step
dλ
differential of integration (1 nm)
3.1.12
diffuse reflectance spectroscopy
DRS
technique used to measure the remitted light from skin or skin remittance.
Note 1 to entry: Using this technique, the UVA absorbance spectrum of a sunscreen product applied on skin in vivo can
be determined.
Note 2 to entry: The term “light” is used generically to describe electromagnetic radiation from both UV and visible
wavelengths of optical spectrum throughout the document. It is differentiated as needed in specific sections of the
document.
ISO 23698:2024(en)
Note 3 to entry: The UV energy that is measured is not energy reflected from the surface of the skin or the applied
sunscreen. The UV energy being measured has passed through the sunscreen, entered the surface of the skin, and been
scattered therein. Some of this energy is remitted back to the surface of the skin through the sunscreen a second time
and picked up by the DRS optical probe. The term “remittance” is used throughout this document whereas historical
use of the term “reflectance” has had precedence in published literature.
3.1.13
erythema action spectrum
E(λ)
relative effects of individual spectral bands of an exposure source causing an erythema response in skin
Note 1 to entry: See Annex E.
3.1.14
hybrid diffuse reflectance spectroscopy
HDRS
method to evaluate the protection provided by a sunscreen product applied on skin in vivo wherein the UVA
Protection Factor is measured by DRS and the UVB part of the spectrum by in vitro thin film spectroscopy,
and the two spectra are merged to form a hybrid absorbance spectrum
Note 1 to entry: The spectral distributions determined by the two different methods are merged to form the hybrid
spectral absorption A (λ).
HDRS
3.1.15
hybridization wavelength
HW
λ
HW
wavelength at which the in vivo DRS spectrum and the in vitro absorbance spectrum are merged
3.1.16
PPD action spectrum
P(λ)
relative effects of individual spectral bands of an exposure source to cause persistent pigment darkening (PPD)
Note 1 to entry: See Annex E.
3.1.17
sun protection factor by hybrid DRS
SPF
HDRS
SPF of a sunscreen product calculated from hybridized UV absorbance spectrum adjusted by spectral ratio
of photo-degradation (SRPD) (λ)
3.1.18
spectral ratio of photo-degradation (λ)
S (λ)
RPD
ratio of the in vitro absorbance spectra (post- and pre-irradiation) representing the photo-degradation of
the sunscreen product as function of wavelength
Note 1 to entry: SRPD(λ) spectrum is 290 nm to 400 nm
3.1.19
subsite
area within a test site where the DRS probe is placed to take the individual skin remittance measurement
denoted by index j
3.1.20
test site
defined area of the skin to which a test sunscreen material is applied and where DRS measurements are
conducted
ISO 23698:2024(en)
3.1.21
Student's t value
t
two tail Student’s t-test critical value for 0,05, with n-1 degrees of freedom
3.1.22
transmittance spectrum by DRS
T (λ)
DRS
in vivo transmittance spectrum of a sunscreen product calculated from DRS as a function of wavelength λ
Note 1 to entry: The in vivo transmittance spectrum is 320 nm to 400 nm.
3.1.23
UVA protection factor by DRS
UVA-PF
DRS
initial UVA protection factor of a sunscreen product calculated using the measured in vivo absorbance
spectrum from DRS before correction for photo-degradation
3.1.24
UVA protection factor by HDRS
UVA-PF
HDRS
UVA protection factor of a sunscreen product calculated from hybridized UV absorbance spectrum adjusted
by SRPD(λ)
3.2 Symbols
I irradiance of remitted UVA from unprotected skin with polychromatic DRS measurement device
u
I irradiance of remitted UVA from sunscreen-treated skin with polychromatic DRS measure-
p
ment device
i index for individual subject
ITA° individual typology angle
I calibrated UVA irradiance
rad,UVA
j index for individual test subsite
k index for individual PMMA plate (in vitro measurement)
l number of subsite measurements on a PMMA plate
m index for individual spot of in vitro measurement
n number of context dependent elements (these elements can be the subjects, the spots on a
PMMA plate or the valid test results)
R (λ) irradiance of remittance spectrum (320 nm to 400 nm) of product-treated skin
p
R(λ) irradiance of remittance spectrum (320 nm to 400 nm) of unprotected skin
u
s scalar multiplier for scaling in vitro spectra for an individual
i
S(λ) spectral irradiance of the light source used to expose the plates
stdev, σ standard deviation of the ln transformed UVA-PF values or the ln transformed SPF
HDRSi HDRSi
values (context dependent)
T (λ) in vitro transmittance spectrum (290 nm to 400 nm) before UV-exposure
vt0
ISO 23698:2024(en)
T (λ) in vitro transmittance spectrum (290 nm to 400 nm) after UV-exposure
vt1
UVA-PF initial UVA protection factor of a sunscreen product calculated using the measured in vivo
DRS
absorbance spectrum from DRS before correction for photo-degradation
UVA-PF UVA protection factor of a sunscreen product calculated from hybridized UV absorbance
HDRS
spectrum adjusted by SRPD
UVA-PF in vitro UVA Protection Factor of a sunscreen product calculated using the absorbance spec-
vt0
trum A
vt0
UVA-PF in vitro UVA Protection Factor of a sunscreen product calculated using the absorbance spec-
vt1
trum A
vt1
vt index for in vitro
λ critical wavelength (including calibration factor)
c
λ raw critical wavelength
c’
λ hybridization wavelength
HW
4 Principle
This method provides a hybrid (in vitro and in vivo) testing procedure to characterize UV protection
provided by sun care preparations. The primary outputs of this test procedure are measures of the spectral
absorbance characteristics of a sunscreen product. Different approaches to generate hybridized absorbance
spectra are available, i.e. monochromatic as well as polychromatic measurement techniques.
The UVA-PF can be predicted by diffuse reflectance spectroscopy (DRS) measuring the UVA absorbance of
skin (320 nm to 400 nm) and has been shown to correlate with in vivo assessment using ISO 24442 (see
also References [5] and [6]), as well as UVA-PFs using ISO24443 (see References [7] to [13]. Because of
the high UVB absorbance characteristics of the stratum corneum and epidermis, the human skin does not
remit enough UVB radiation for absorbance measurements. Therefore, the spectral absorbance ‘shape’ in
the UVB region must be assessed separately by in vitro thin film transmittance spectroscopy. To account
for sunscreen products photo-instability of the sunscreen under evaluation, the same approach used in
ISO 24443 is applied. The in vitro thin film sunscreen sample is subjected to a controlled dose of simulated
sunlight radiation to determine the shape of the spectrum after UV exposure which is used to adjust the
hybrid diffuse reflectance spectroscopy (HDRS) absorbance spectrum.
In order to obtain a full UV absorbance spectrum, the in vitro absorbance is scaled to match the DRS
absorbance values and then the in vitro UVB portion is mathematically attached to the UVA portion from
the DRS technique. This HDRS absorbance spectrum is then used to calculate the UVA-PF, SPF and critical
[10],[11]
wavelength (CW) of the sunscreen products being tested .
Samples submitted for testing should not have a SPF or UVA-PF target or other protection category
description.
5 Apparatus and test method
5.1 In vitro UV spectrophotometer
The in vitro UV spectrophotometer shall follow the specifications and calibration procedure as described in
Annex B.
ISO 23698:2024(en)
5.2 In vitro substrate/plate
The substrate/plate is the material to which the test product is applied for the in vitro part of this method.
Polymethylmethacrylate (PMMA) plates with one rough side of the substrate shall be used and prepared as
specified in Annex D.
5.3 In vivo diffuse reflectance spectrometers (DRS) specifications
Common elements for the monochromatic and polychromatic DRS systems include the following.
5.3.1 Optical light source
A short arc xenon bulb emitting continuous radiation over the range of 290 nm to 400 nm is recommended.
A maximum exposure dose of 10 J/m eff dose shall not to be exceeded for any measurement subsite. The
maximum exposure irradiance at skin surface shall be less than 5 mW/cm . Calibration of radiometers
for this evaluation shall be done in accordance with Annex C. The spectral irradiance of the illuminating
source shall be evaluated once per year to validate that the maximum exposure irradiance and dose are not
exceeded during a subsite measurement.
5.3.2 DRS illumination/Collection fibres
A UV grade fused silica bifurcated fibre probe comprised of a fibre arrangement as described in Annex I,
with approximately 1,5 m common probe length and two 0,5 m short arms (one for excitation and one for
emission) is recommended. The area of the common optical probe shall be less than 1,2 cm . The common
bundle shall have ≥ 800 individual fibres with a ratio of illuminating fibres to collection fibres between
45:55 and 55:45.
Annular fibre optic bundles: the centre illuminating fibre bundle shall have a 200 μm spacer between it and
the surrounding collection fibres.
Randomized fibre optic bundles: ≥ 95 % of the illuminating fibres shall be adjacent to a collection fibre with
a minimum spacing between the centres of adjacent fibres of 280 μm. See Annex I for the fibre configuration.
5.3.3 Detector system
A bi-alkali photo multiplier cathode detector (PMT) is recommended. To obtain a better signal to noise ratio
it is recommended that the detector be cooled (i.e. -20 °C). The PMT temperature is recommended to be
approximately 40 °C lower than room temperature.
5.3.4 Sensitivity requirements
A linear response detection shall be at least 5 decades (100 000:1), (6 decades (1 000 000:1) are
recommended) in the range of 290 nm to 400 nm. Usually, this can be achieved by a double monochromator
spectrophotometer with a good stray light rejection and an appropriated, cooled PMT. The chosen voltage of
the PMT (gain) should allow a high sensitivity at lower wavelengths (<320 nm) and avoid an overload of the
PMT at higher wavelengths (>370 nm).
5.3.5 Monochromatic DRS system monochromators
Monochromators used for excitation or emission can be single or double monochromators with a wavelength
accuracy of ±0,1 nm. The ratio of stray light (at a distance from the peak wavelength that is 10 x the
bandwidth at half maximum of the laser line peak irradiance), to the peak irradiance of a laser line shall be
-5
less than 5 x 10 . Furthermore, installed filters shall be used to block any visible light from entering the
photomultiplier detector. The system shall have the specifications as described in 5.3.1 to 5.3.4.
5.3.6 Polychromatic DRS system
In vivo polychromatic DRS measurements shall be conducted using a light source with spectral output as
described in Annex E and a PMT detector system with a response spectrum similar to the human persistent
ISO 23698:2024(en)
pigment darkening (PPD) action spectrum as described in Annex E. Any differences between the PMT
detector system X spectral output of the source and the human PPD action spectrum X spectral output
of the source shall be corrected with a spectral mismatch calculation routine. The system shall have the
specifications as described in 5.3.1 to 5.3.4.
A visible light (“black glass”) blocking filter is recommended to be included before a broad-spectrum photo
multiplier cathode detector to eliminate measurement of visible fluorescence using the polychromatic DRS
system and to shape the action spectrum of the detector to be similar to the skin’s PPD action spectrum as
described in Annex E.
5.4 Monitoring the DRS systems
5.4.1 Monochromatic system
Wavelength accuracy shall be checked regularly either with a holmium oxide filter (according to B.2) or with
a low-pressure mercury, “cold quartz” or equivalent lamp following usual calibration procedures.
A periodic inspection of the DRS wavelength accuracy and fibre output irradiance at least once per year shall
be conducted using calibrated equipment by a trained, competent and suitably qualified person (internal or
external). The optical fibre bundle shall be inspected at least once per year to validate compliance with 5.3.2
and to check for broken fibres.
5.4.2 Polychromatic system
The illumination beam of the polychromatic DRS system shall be checked periodically to assure conformance
to the specifications described for the UVA radiation source in Annex E. A spectroradiometric inspection
of the spectrum shall be conducted at least once per year by a trained, competent, and suitably qualified
person (internal or external) using a system calibrated to a traceable national or international calibration
standard lamp. The optical bundle shall be inspected at least once per year to validate compliance with 5.3.2
and to check for broken fibres.
5.5 Test method
5.5.1 General
DRS measurements and product application assessment are recommended to be carried out in stable
conditions, with the room temperature maintained between (23 + 3) °C.
5.5.2 Subject exclusion criteria
Exclusion criteria shall be checked before testing.
The following conditions shall automatically disallow inclusion of a subject in the test group:
a) children or persons below the locally legal age of consent;
b) subjects with systemic dermatological conditions in the test area (including dysplastic nevi);
c) subjects having excessive hair in the area on the test on the day of testing (may be shaved up to 3 days
prior to the test day, or cut or clipped on the test day);
d) subjects with average individual typology Angle (ITA°) <28°;
e) subjects having UV-exposures applied to the test sites, [i.e. SPF (ISO 24444, UVA-PF (ISO 24442], photo-
allergy or photo-toxicity tests, or sun-tanning) within the past 8 weeks and having pigmentation marks
or erythema in the test sites.
ISO 23698:2024(en)
5.5.3 Skin colour of the test subjects
Test subjects shall have an ITA° value ≥ 28° as determined by colorimetric methods with the same acceptance
criteria for number of subjects in each of the three ITA° bands (28°to 40°, 41°to 55°, and ≥56° as stipulated
in ISO 24444:2019, 5.1.2). The average of the subjects making up a test panel shall have an ITA
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...