In the European Union, there are recommendations that require that alternatives to use of human volunteers be pursued for the testing of sunscreens. These in vitro tests are also of particular use for the screening of products for R&D purposes. A number of methods have been in use from 1990’s(1), based on the use of thin films of products being applied to a rigid substrate and now measured with special purpose spectrophotometers such as a LabSphere® or Solar Light SPF 290®.
Although useful for formulation comparative purposes, the in vitro test method has suffered from not fully correlating with in vivo SPF. In order to advance this methodology, two in vitro SPF methods, ISO 23675(2) and ISO 23698(3) are currently under development as Work Items.
Both in vitro methods have been supported by publications and an outline of the methodology can be seen there(4,5), even though the ISO drafting of the two in-vitro methods is not complete and formalised. Below is a comparison of the in vitro test methods available.
Comparison of 3 in vitro SPF Test Methods:
As active participants in international technical review committees, solar experts from Eurofins Cosmetics & Personal Care laboratories participate in validation cycles of various standards relating to solar tests (whether in-vivo or in-vitro) and facilitate their implementation in Eurofins sites. Consistent inter- and intra-laboratory harmonisation guarantees homogeneous test methods for all solar products and optimal quality across all our sites. This optimises the performance of multicenter solar studies.
Our regulatory expertise, coupled with our years of experience in toxicology, physico-chemical analyses, ecotoxicity, biodegradability, and OTC product support make Eurofins Cosmetics & Personal Care THE solar center of excellence!
References
1. Diffey B, Robson J. A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum. J Soc Cosm Chem. 1989;40(5):127-133.
2. ISO 23675 Cosmetics – Sun protection test methods – In Vitro Determination of Sun Protection Factor (SPF).
3. ISO 23698 Cosmetics – Sun protection test methods -Measurement of the Sunscreen Efficacy by Diffuse Reflectance Spectroscopy.4. Pissavini M, Tricaud C, Wiener G, Lauer A, Contier M, Kolbe L, Trullás Cabanas C, Boyer F, Nollent V, Meredith E, Dietrich E, Matts PJ. Validation of an in vitro sun protection factor (SPF) method in blinded ring-testing. Int J Cosm Sci. 2018;40(3):263-268.
5. Ruvolo E, Aeschliman L, Cole C. Evaluation of sunscreen efficacy over time and re-application using hybrid diffuse reflectance spectroscopy. Photodermatol Photoimmunol Photomed. 2020 Feb 6. DOI: 10.1111/phpp.12535.
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