SPF alternative testing methods

May 9, 2022 – Sunscreen products must ensure high protection of consumers against UV radiation. Hence, in the EU, they have to meet specific requirements in terms of efficacy. For this purpose, the European Committee for Standardization (CEN) elaborated the ISO standard 24444, which describes an in vivo testing method for the determination of sun protection factor (SPF) of sunscreen products. Therefore, manufacturers should follow the latest version of this standard, ISO 24444:2019/AMD 1:2022, published on March 18, 2022.


In vivo vs. in vitro testing methods

ISO standard ISO 24444:2019/AMD 1:2022 identifies an in vivo testing method using volunteers. In fact, in vivo indicates tests conducted on a living body. Conversely, in vitro means “in glass” in Latin and refers to tests performed outside of a living organism.  However, in the Recommendation 2006/647/EC, the European Commission highlighted that testing in vivo raises ethical concerns. Thus, in vitro testing methods should be preferred.

To meet this need, in the last years, the cosmetic industry has worked on alternative SPF testing methods. The challenge, however, was to develop in vitro methods that:

  • Provide equivalent and comparable results to the in vivo method featured in ISO 24444:2019/AMD 1:2022;
  • Give replicable results;
  • Consider photo-degradation.


New in vitro SPF tests

As a result, a consortium of 28 partners from personal care companies as well as laboratories   is currently working on the evaluation and standardization of two new in vitro tests:

  • In Vitro ‘Double Plate’ Method;
  • Hybrid Diffuse Reflectance Spectroscopy (HDRS)

Laboratory validation data was provided to ISO-working group to substantiate the ongoing development of an ISO Standard Method. Those tests will likely be published as final ISO standards in 2025. Furthermore, several other methods are currently under development.

By this time, UVA-PF can be calculated following the published ISO standards:

  • ISO 24443:2021 on the determination of sunscreen UVA protection in vitro; or
  • ISO 24442:2022 on the in vivo determination of sunscreen UVA protection.


In light of the above, in March 2022, Cosmetics Europe issued a recommendation asking laboratories and interested parties to start training on the two new in vitro testing methods. But it is important to remind that until their official publications, ISO 24444:2019/AMD 1:2022 remains the gold standard.


In the COSlaw Library of Documents, there is a section dedicated to sunscreen products. Click here to check all the documents uploaded, including ISO 24444:2019/AMD 1:2022 and Cosmetics Europe recommendation mentioned above. But, of course, you will find many more.

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