Overview
ISO 24444:2019 - "Cosmetics - Sun protection test methods - In vivo determination of the sun protection factor (SPF)" specifies the standardized laboratory method for measuring the sun protection factor (SPF) of sunscreen products using human volunteers. The method quantifies protection against UV-induced erythema (sunburn) by comparing the minimal erythemal dose (MED) on unprotected skin versus skin treated with the product. ISO 24444:2019 updates and harmonizes earlier protocols to improve reproducibility across test sites.
Key technical topics and requirements
- Scope: Applies to topical products that absorb, reflect or scatter ultraviolet (UV) radiation and are intended for contact with human skin.
- SPF principle: SPF is calculated as a ratio of energies (MED) required to induce erythema with and without sunscreen applied (in vivo human testing).
- Test subjects: Selection is based on skin colour typing using the individual typology angle (ITA°); the test panel average ITA° must lie within a defined range (41° to 55°). Ethical consent, age restrictions and participation frequency rules are mandated.
- UV solar simulator and apparatus: Requirements for UV sources (spectral quality, irradiance) and beam uniformity are specified. New methods define large and small beam uniformity testing with a minimum uniformity requirement of ≥ 90%.
- Minimal Erythemal Dose (MED): Clear definitions and revised criteria for identifying the MED (first perceptible unambiguous erythema 16–24 hours post‑exposure).
- Procedure and application: Detailed instructions on test conditions, subject positioning, amount and method of product application, MED assessment timing, and rejection/test-failure criteria.
- Reference sunscreens: Three new validated reference formulations (P5, P6, P8) included for panels testing products with SPF ≥ 25.
- Calculations, statistics and reporting: Methods for individual and product SPF calculation, statistical validation criteria, and required test report content (sample forms in the annexes).
Practical applications and users
- Cosmetic and sunscreen manufacturers: For product development, labeling, quality control and regulatory submissions.
- Independent test laboratories (in vivo SPF testing labs): To perform validated, reproducible SPF testing using standardized methods and reporting.
- Regulatory bodies and compliance teams: To assess claims, ensure consumer safety and harmonize labeling across markets.
- R&D and clinical teams: To compare formulations, benchmark efficacy and support product claims.
Keywords: ISO 24444:2019, SPF testing, sun protection factor, in vivo determination, sunscreen testing, UV solar simulator, MED, skin typing (ITA°).
Related standards
- ISO/TR 26369 (technical report referenced for related methods and harmonization across SPF test protocols).
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