ISO/CIE FDIS 17166

• Abstract:

  This document specifies the erythema reference action spectrum, ser(λ), and the standard erythema dose (SED).

• Status: Not Published
• ICS: 17.180.20 - Colours and measurement of light
• Technical Committee: CIE - International Commission on Illumination
• Drafting Committee: CIE - International Commission on Illumination
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 28-Aug-2026
• Completion Date: 28-Aug-2026

• Revises: ISO/CIE 17166:2019 - Erythema reference action spectrum and standard erythema dose
• Effective Date: 22-Mar-2025

Overview

ISO/CIE FDIS 17166: Erythema Reference Action Spectrum and Standard Erythema Dose is an international standard developed by the International Organization for Standardization (ISO) and the International Commission on Illumination (CIE). This document specifies the erythema reference action spectrum, denoted as ser(λ), and defines the standard erythema dose (SED) - a critical reference in quantifying the erythemogenic (skin-reddening) potential of ultraviolet (UV) radiation. The standard is widely applied in photobiology, photomedicine, metrology, health safety, and industries where assessment and classification of UV exposure risks are essential.

With an updated introduction, clarity on formulas, and revised terminology, the 2026 edition closely aligns with current research and applications concerning UV-induced erythema and skin safety.

Key Topics

• Erythema Reference Action Spectrum (ser(λ)):
  Defines the relative effectiveness of UV radiation at different wavelengths to produce erythema (skin redness) in human skin, ranging between 250 nm and 400 nm.
• Erythema Spectral Weighting Function:
  This function serves as a weighting factor for the biological effectiveness of incident radiation, normalized to 1 at its maximum for precise and reproducible assessments.
• Erythemal Irradiance:
  Expresses the amount of UV radiation, spectrally weighted for erythemal effectiveness, received per unit area, measured in watts per square metre (W·m⁻²).
• Erythemal Dose and Standard Erythema Dose (SED):
  • Erythemal dose integrates erythemal irradiance over time, reported in joules per square metre (J·m⁻²).
  • Standard erythema dose (SED) quantifies UV exposure with 1 SED being equivalent to 100 J·m⁻² of erythemally effective radiant exposure. The SED offers a standardized, objective metric, independent of individual biological variability.
• Minimal Erythema Dose (MED):
  Distinguished from SED, MED is the variable UV dose that causes just perceptible redness in an individual’s skin. It is influenced by personal sensitivity and should not be used as a standard measurement in regulatory or technical contexts.

Applications

The implementation of ISO/CIE FDIS 17166 facilitates:

• UV Exposure Assessment:
  Used in environmental monitoring, occupational health, and dermatology to quantify and categorize human exposure to erythemogenic UV radiation.
• Safety Standards Development:
  Provides the scientific basis for safety guidelines in workplaces, medical phototherapy, and the safe design of UV-emitting devices, as well as sunscreen and protective clothing evaluation.
• Metrology and Instrument Calibration:
  Ensures the comparability of UV measurements by providing a standardized reference for quantifying erythemal effectiveness across instruments and laboratories globally.
• Research and Clinical Studies:
  Enables consistency in research related to photobiology, skin cancer prevention, and the study of skin responses across different populations and light environments.
• Public Health Communication:
  Supports public awareness campaigns and policy-making around the risks associated with UV exposure by establishing clear, standardized reference doses.

Related Standards

• CIE S 017 - International Lighting Vocabulary:
  Provides essential terminology for light and lighting, including photobiological concepts.
• CIE 125:1997 - Standard Erythema Dose: A Review:
  Offers a foundational review of the SED concept.
• Fitzpatrick Skin Type Classification:
  Commonly referenced in studies and guidelines for interpreting individual and population-level responses to UV exposure.
• ISO/TC 274 - Light and Lighting:
  Oversees standardization work relevant to photometry, colorimetry, and photobiological safety.

ISO/CIE FDIS 17166 is an essential standard for all professionals and organizations engaged in UV safety, phototherapy, environmental monitoring, and the development or regulation of UV-emitting products. By providing a harmonized and objective framework for erythema assessment, it advances safety, comparability, and clarity in UV risk management worldwide.

FINAL DRAFT
International
Standard
ISO/CIE FDIS
CIE
Erythema reference action
Secretariat: CIE
spectrum and standard erythema
Voting begins on:
dose
2026-08-28
Spectre d'action érythémale de référence et dose érythémale
Voting terminates on:
normalisée
2026-10-23
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Reference number
FINAL DRAFT
International
Standard
ISO/CIE FDIS
CIE
Erythema reference action
Secretariat: CIE
spectrum and standard erythema
Voting begins on:
dose
Spectre d'action érythémale de référence et dose érythémale
Voting terminates on:
normalisée
Member bodies are requested to consult relevant national interests in ISO/TC
274 before casting their ballot to the e-Balloting application.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
© ISO/CIE 2026
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
IN ADDITION TO THEIR EVALUATION AS
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
or ISO’s member body in the country of the requester
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
ISO copyright office CIE Central Bureau TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
CP 401 • Ch. de Blandonnet 8 Babenbergerstraße 9/9A • A-1010 Vienna
CH-1214 Vernier, Geneva
Phone: [phone] Phone: [phone]
Fax: [phone]
Email: [e-mail] Email: [e-mail]
Website: www.iso.org Website: www.cie.co.at
Published in Switzerland Reference number
© ISO/CIE 2026 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Concept of erythemal irradiance and dose . 3
4.1 Erythemal irradiance .3
4.2 Erythema spectral weighting function.3
4.3 Standard erythema dose .4
Bibliography . 6

© ISO/CIE 2026 – All rights reserved
iii
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 International Commission on Illumination (CIE) is an international scientific, technical and cultural
organization, a member of the International Science Council (ISC), and a standards developing body
recognized by the International Bureau for Weights and Measures (BIPM), as well as by ISO and the
IEC. The CIE serves its global membership, the CIE National Committees, and publishes authoritative,
consensus-based, and balloted documents (International Standards, Technical Reports, Technical Notes,
Position Statements). The CIE’s work embraces such fundamental topics as vision, photometry, colorimetry,
photobiology and photochemistry, involving natural and anthropogenic optical radiation over the UV, visible
and IR regions of the spectrum; and application topics covering all usage of light, indoors and out, including
environmental and aesthetic effects, as well as means for the production and control of light and radiation.
Furthermore, optical, visual and metrological aspects of the communication, processing and reproduction of
images, using all types of analogue and digital imaging devices, storage media and imaging media are also
covered by CIE.
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).
ISO and CIE draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and CIE take 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 and CIE 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 and CIE 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 Division 6, Photobiology and Photochemistry, of the International
Commission on Illumination (CIE) in cooperation with Technical Committee ISO/TC 274, Light and lighting,
under the Partner Standards Development Agreement established between ISO and CIE.
This second edition of ISO/CIE 17166 cancels and replaces the first edition (ISO/CIE 17166:2019), which has
been technically revised.
The main changes are as follows:
— Introduction has been rewritten;
— Formula (3) has been added, and the relationship with Formula (4) has been added;
— Figure 1 has been added;
— history of the erythema action spectrum has been moved to a note;
— reference for classification of the skin types has been added;

© ISO/CIE 2026 – All rights reserved
iv
— minor editorial changes.
Any feedback or questions on this document should be directed to the user’s national standards
body and/or the user’s CIE National Committee. A complete listing of these bodies can be found at
www.iso.org/members.html and at www.cie.co.at/.

© ISO/CIE 2026 – All rights reserved
v
Introduction
Knowledge of the wavelength range is crucial in ultraviolet (UV) dose estimation, since elicitation of
erythema varies within four orders of magnitude between wavelengths of 250 nm and 400 nm. Thus, the
radiant exposure causing a just perceivable erythema at 250 nm will occur at about 1/1 000 of the radiant
exposure at 400 nm.
In practice, being irradiated with e.g. an indoor lighting device emitting partly in the UV-A, an erythemal
response may be seen only in people suffering from pathological photosensitivity. The same radiant
exposure from the midday sun at e.g. latitudes near the Equator would result in marked erythema in most
individuals with untanned, light skin. Thus, expressing UV exposure as an erythemally weighted quantity is
useful and appropriate in fields such as photobiology and photomedicine.
The standardized measure for erythemogenic UV radiation is t
...

Date: 2025-09-16
ISO/CIE/DIS FDIS 17166:2025(en)
CIE
Secretariat: CIE
Date: 2026-08-14
Erythema reference action spectrum and standard erythema dose
Spectre d’action erithémaled'action érythémale de référence et dose erithémaleérythémale normalisée
MUST BE USED MUST BE USED
Member Member bodbodies are requies are requeestedsted to cons to consult relult relevant evant nationnational intal inteerestsrests in I in ISOSO//TC 274 bTC 274 before castinefore casting g ththeeir ir
FOR FINAL FOR FINAL
ballot toballot to the the ee--BallBallotinoting g aapplpplication.ication.

The publication of this document is conditional upon the resolution of open issues regarding ownership, copyright and
licensing and the development of appropriate “copyright notices” as in this section for CIE-originating, CIE-owned and
CIE-maintained documents.
FDIS stage
MUST BE USED MUST BE USED
FOR FINAL FOR FINAL
ISO/CIE DISFDIS 17166:20252026(en)
© ISO/CIE 2026
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
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
MUST BE USED
FOR FINAL
(copyright notice to be resolved, document developed solely by the CIE)
© ISO/CIE 2026 – All rights reserved
iii
ISO #####-#:####(X/CIE FDIS 17166:2026(en)
Contents
Foreword . v
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Concept of erythemal irradiance and dose . 3
4.1 Erythemal irradiance . 3
4.2 Erythema spectral weighting function . 4
4.3 Standard erythema dose . 6
Bibliography . 7

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Concept of erythemal irradiance and dose . 3
4.1 Erythemal irradiance . 3
4.2 Erythema spectral weighting function . 4
4.3 Standard erythema dose . 4
Bibliography . 5

iv © ISO #### /CIE 2026 – All rights reserved
iv
ISO/CIE DISFDIS 17166:20252026(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, For
standards in relation to light and lighting, ISO collaborates closely with the International Commission on
Illumination (CIE) and recognizes the CIE as the relevant international standardizing body according to the
Council resolution 19/1984.
The International Commission on Illumination (CIE) is an international scientific, technical and cultural
organization, a member of the International Science Council (ISC), and a standards developing body
recognized by the International Bureau for Weights and Measures (BIPM), as well as by ISO and the IEC. The
CIE serves its global membership, the CIE National Committees, and publishes authoritative, consensus-based,
and balloted documents (International Standards, Technical Reports, Technical Notes, Position Statements).
The CIE'sCIE’s work coversembraces such fundamental topics such as vision, photometry, colorimetry,
photobiology and photochemistry, involving natural and anthropogenic optical radiation inover the
ultraviolet (UV),, visible and infrared (IR) regions of the spectrum. It also covers applications involving the
use; and application topics covering all usage of light, indoors and outdoorsout, including environmental and
aesthetic effects of light, as well as means for the production and control of light and radiation. Furthermore,
optical, visual and metrological aspects of communicatingthe communication, processing and
reproducingreproduction of images, using all types of analogue and digital imaging devices, storage media and
imaging media are also covered by the CIE.
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 documentdocuments 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 and CIE draw- attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO and CIE take 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 and CIE 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.www.iso.org/patents. ISO and CIE 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.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Division 6, Photobiology and Photochemistry, of the International Commission
on Illumination (CIE). ISO and CIE hold a Partner Standards Development Agreement and related work is
mostly implemented) in cooperation with Technical Committee ISO/TC 274, Light and lighting., under the
Partner Standards Development Agreement established between ISO and CIE.
MUST BE USED
FOR FINAL
(copyright notice to be resolved, document developed solely by the CIE)
© ISO/CIE 2026 – All rights reserved
v
ISO #####-#:####(X/CIE FDIS 17166:2026(en)
This second edition of ISO/CIE 17166 cancels and replaces the first edition (ISO/CIE 17166:2019), of which it
constitutes a minor revision. has been technically revised.
The main changes are as follows:
— the Introduction has been rewritten;
— Formula (3)(3) has been added, and the relationship with Formula (4)(4) has been added;
— Figure 1Error! Reference source not found. has been added;
— history of the erythema action spectrum has been moved to a note;
— reference for classification of the skin types has been added;
— minor editorial changes.
Any feedback or questions on this document should be directed to the user’s national standards body and/or
the user’s CIE National Committee. A complete listing of these bodies can be found at
www.iso.org/members.html and at www.cie.co.at.www.iso.org/members.html and at www.cie.co.at/.

vi © ISO #### /CIE 2026 – All rights reserved
vi
ISO/CIE DISFDIS 17166:20252026(en)
Introduction
Knowledge of the wavelength range is crucial in ultraviolet (UV) dose estimation, since elicitation of erythema
varies within four orders of magnitude between wavelengths of 250 nm and 400 nm. Thus, the radiant
exposure causing a just perceivable erythema at 250 nm will occur at about 1/10001 000 of the radiant
exposure at 400 nm.
In practice, being irradiated with e.g. an indoor lighting device emitting partly in the UV-A, an erythemal
response may be seen only in people suffering from pathological photosensitivity. The same radiant exposure
from the midday sun at e.g. latitudes near the Equator would result in marked erythema in most individuals
with untanned, light skin. Thus, expressing UV exposure as an erythemally weighted quantity is useful and
appropriate in fields such as photobiology and photomedicine.
The standardized measure for erythemogenic UV radiation is the "standard erythema dose (SED)". While the
term "minimal erythema dose (MED)" is sometimes used as a measure of erythemal radiation, it only
expresses the variable nature of individual sensitivity to UV radiation, and as such is not a standard measure.
The term "MED" is used in studies in which humans and animals are observed, i.e. when the individual
sensitivity is the endpoint of interest.

MUST BE USED
FOR FINAL
(copyright notice to be resolved, document developed solely by the CIE)
© ISO/CIE 2026 – All rights reserved
vii
DRAFT International Standard ISO/CIE DIS 17166:2025(en)

Erythema r
...