In December 2024, the International Organization for Standardization (ISO) introduced two new methods for assessing the Sun Protection Factor (SPF) of cosmetic products. These new standards reflect the cosmetic industry’s commitment to developing in vitro alternatives to traditional in vivo SPF testing methods.
In Vivo vs. In Vitro Testing
Until December 2024, the standard method for SPF testing was EN ISO 24444:2020, an in vivo method that required human volunteers. In contrast, in vitro – Latin for “in glass” – refers to testing conducted outside a living organism.
The European Commission, in Recommendation 2006/647/EC, highlighted ethical concerns associated with in vivo testing and encouraged the development of in vitro alternatives. Over recent years, the suncare industry has worked extensively on alternative SPF testing methods, facing key challenges such as:
- Ensuring results equivalent and comparable to those obtained via ISO 24444:2019/AMD 1:2022 (the in vivo standard).
- Achieving repeatable and reproducible outcomes.
- Considering photo-degradation effects.
The new ISO standards
To address these challenges, a consortium of 28 partners – including personal care companies and laboratories – collaborated to evaluate and standardise two new SPF testing methods, which have now been officially published:
- The Double Plate Method (DPM) – a fully in vitro approach outlined in the new ISO 23675:2024. Developed by Cosmetics Europe expert members, this method eliminates the need for human volunteers while providing reliable, repeatable, and reproducible results. It is suitable for emulsions and alcoholic one-phase formulations but not applicable to powders, compressed products, or sticks. Additionally, this method does not evaluate the water resistance of sun protection products, but it is exclusively for the determination of a static sun protection factor.
- Hybrid Diffuse Reflectance Spectroscopy (HDRS) – a hybrid method outlined in ISO 23698:2024 that enables a non-invasive optical assessment of sunscreen products without requiring a physiological skin response. This method evaluates SPF, UVA protection factor, and critical wavelength without relying on biological reactions. It is suitable for emulsions and single-phase formulations, though its effectiveness for powder-based sunscreens has not yet been assessed. The standard outlines specifications for determining the absolute spectral absorbance characteristics of a sunscreen product on the skin to assess sunburn and UVA protection. It applies to products containing components that absorb, reflect, or scatter ultraviolet (UV) rays and are intended for direct skin contact.
Both methods show correlation with in vivo assessments based on ISO 24444.
Do you have questions on compliance of cosmetics in the EU, UK, USA, and Canada? Contact us here or at coslaw@obelis.net.
References
Cosmetics Europe. (2022). Cosmetics Europe Recommendation N.26 on the use of alternative methods to ISO 2444:2019. Retrieved on 7 February 2025.
European Commission. (2006). Commission Recommendation of 22 September 2006 on the efficacy of sunscreen products and the claims made relating thereto. Retrieved on 7 February 2025.
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