ISO 24443-2021 (2022) PDF

Full title and description

ISO 24443:2021 — Cosmetics — Determination of sunscreen UVA photoprotection in vitro. This international standard specifies a reproducible in vitro procedure to characterise the UVA photoprotection of topical sunscreen products by producing a spectral UV absorbance curve and deriving parameters such as the in vitro UVA protection factor (UVA‑PF), critical wavelength and UVA absorbance proportionality; it relies on scaling of in vitro spectral results to an in vivo SPF measurement and is not applicable to powder (pressed or loose) products.

Abstract

ISO 24443:2021 provides laboratory procedures, instrumentation and calculation methods to evaluate the magnitude and spectral distribution of UVA protection offered by sunscreens applied to standard PMMA substrates. The method yields an in‑vitro UVA‑PF and optional outputs for critical wavelength and proportionality assessments, and includes requirements for plate preparation, application, spectrophotometric measurement (290–400 nm) and photostability assessment.

General information

• Status: Published (current international standard; corrected versions exist).
• Publication date: 6 December 2021 (original edition; corrected version noted 2022).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 71.100.70 (Cosmetics, toiletries) — also referenced with diagnostics / in vitro test systems classifications.
• Edition / version: ISO 24443:2021 (first edition 2021; corrected 2022 corrections published for the English/French texts).
• Number of pages: Approximately 36 pages (English edition).

Key bibliographic and edition details above are based on the ISO publication and national distributor records.

Scope

This standard specifies an in‑vitro test procedure to characterise UVA photoprotection of topical sunscreen products by measuring spectral absorbance between 290 nm and 400 nm (1 nm steps) on standardised PMMA plates, performing measurements before and after defined UVA irradiation to assess photostability, and calculating metrics such as UVA‑PF and critical wavelength. The method is intended for liquid, cream, lotion and other non‑powder sunscreens and relies on in‑vivo SPF results for scaling; it excludes powder (pressed or loose) products.

Key topics and requirements

• Spectral measurement range and resolution: absorbance recorded from 290 nm to 400 nm, typically at 1 nm intervals.
• Substrate and application: use of standardised PMMA plates (moulded or sandblasted) with specified surface characteristics and controlled product application and drying conditions.
• Scaling to in vivo SPF: in‑vitro absorbance spectrum is scaled to a static in‑vivo SPF value (ISO 24444 or validated equivalent) to produce meaningful UVA‑PF estimates for labelling/regulatory purposes.
• Photostability assessment: optional/required measurements before and after specified UVA exposure to determine post‑irradiation UVA‑PF and photostability behaviour.
• Calculations and outputs: procedures to compute UVA‑PF, critical wavelength (λc, 90% area), UVA absorbance proportionality and related statistics (including confidence interval rules and criteria for additional plate replicates).
• Quality control and validation: instrument calibration, reference materials (designated reference sunscreens), acceptance criteria, and laboratory performance checks to ensure reproducibility and comparability.

These technical requirements are drawn directly from the test method and its normative annexes.

Typical use and users

Sunscreen and cosmetic manufacturers, independent testing laboratories, regulatory authorities, product development scientists and quality assurance teams use ISO 24443 to substantiate UVA‑related product claims, support labelling decisions, perform batch or formulation comparisons, and investigate photostability. The method is commonly used alongside in‑vivo SPF data for a complete picture of broad‑spectrum protection.

Related standards

Closely related documents include ISO 24444 (in vivo determination of SPF), other ISO/CEN guidance on UVA testing and national or regional adaptations (EN ISO variants). The ISO 24443 method evolved from earlier COLIPA/industry in‑vitro UVA procedures and is often referenced together with in‑vivo SPF standards when establishing broad‑spectrum or UVA classification claims. Recent amendments and corrigenda (corrected 2022 text and later formal amendments) should be checked when preparing test protocols.

Keywords

UVA, UVA‑PF, sunscreen, in vitro, photoprotection, PMMA plate, spectrophotometer, critical wavelength, photostability, ISO 24443, sunscreen testing

FAQ

Q: What is this standard?

A: ISO 24443:2021 is an international laboratory method for determining the UVA photoprotection characteristics of topical sunscreen products using an in‑vitro absorbance‑based procedure on standard substrates.

Q: What does it cover?

A: The standard covers sample application to PMMA plates, spectrophotometric measurement across 290–400 nm, optional pre/post UVA irradiation for photostability, calculations to derive an in‑vitro UVA‑PF, critical wavelength and proportionality metrics, and laboratory validation/quality control procedures. It excludes powder cosmetics.

Q: Who typically uses it?

A: Manufacturers, contract testing laboratories, regulators, R&D scientists and QA personnel use ISO 24443 for claim substantiation, product development, and compliance checks related to UVA protection.

Q: Is it current or superseded?

A: The published edition is ISO 24443:2021 (with corrected text issued in 2022). Users should check for any amendments or corrigenda issued after 2021 — there have been formal amendment activities and national/adopted versions circulated; confirm the latest corrective or amendment documents before finalising protocols.

Q: Is it part of a series?

A: Yes — it is commonly used in combination with ISO 24444 (in vivo SPF determination) and other ISO or EN methods for complete UV protection performance assessment and labelling.

Q: What are the key keywords?

A: UVA‑PF, UVA photoprotection, in vitro sunscreen testing, PMMA plate method, spectrophotometry, critical wavelength, photostability, UV absorbance spectrum.