Overview
ISO 23698:2024 - Cosmetics - Measurement of the sunscreen efficacy by diffuse reflectance spectroscopy - defines a laboratory and human-subject procedure to characterize sunscreen performance using diffuse reflectance spectroscopy (DRS). The standard enables estimation of sun protection factor (SPF), UVA protection factor (UVA‑PF) and critical wavelength (CW) from measured spectral absorbance characteristics without requiring biological (erythema) endpoints. It applies to emulsions and single‑phase topical products intended for contact with human skin and is not evaluated for powder sunscreen formulations.
Key technical topics and requirements
ISO 23698 covers the full measurement workflow and technical requirements, including:
- Principle and instrumentation: use of in vitro UV spectrophotometers, in vitro substrates/plates (e.g., plate specifications), and in vivo DRS system specifications (monochromatic and polychromatic systems).
- Calibration and verification: calibration checks for spectrophotometers, solar simulator irradiance and radiometer procedures, optical fibre calibration and plate transmittance tests.
- Test method elements: subject selection and exclusion criteria, skin colour considerations, ethics and consent, technician training, product application and spreading procedures, protected/unprotected skin remittance measurements.
- Spectral data processing: determination of absolute spectral absorbance A(λ), hybridization of in vivo and in vitro spectra, spectral ratio of photo‑degradation, and calculations to estimate SPF, UVA‑PF and critical wavelength.
- Quality, statistics and reporting: statistical criteria, data rejection and test failure criteria, reference sunscreen formulations, and a standardized ISO 23698 test report format.
Practical applications and who uses this standard
ISO 23698 is intended for organizations that need robust, non‑biological assessment of sunscreen performance:
- Sunscreen and cosmetic manufacturers - product development, formulation optimization, and substantiation of SPF/UVA claims.
- Independent testing laboratories - accredited DRS testing and routine QC of sunscreen batches.
- Regulatory bodies and compliance teams - evaluation of label claims and conformity assessment without mandatory in vivo testing.
- R&D and photobiology groups - spectral characterization of UV filters, photostability studies and comparison with in vivo methods (e.g., ISO 24444).
Using ISO 23698 supports consistent, reproducible in vitro sunscreen testing, faster claim substantiation and reduced reliance on biological endpoints while providing spectral metrics (SPF, UVA‑PF, CW) relevant to human skin protection.
Related standards
- ISO 24444 - Sun protection factor (SPF) test method (in vivo)
- Other ISO/CEN cosmetics test method standards referenced within ISO 23698 for calibration, ethics and reporting
Keywords: ISO 23698, sunscreen efficacy, diffuse reflectance spectroscopy, SPF measurement, UVA‑PF, critical wavelength, in vitro sunscreen testing, spectral absorbance, cosmetic standards.
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