Validating Alternative SPF Test Methods

Two years ago, the current authors published the article, “SPF Assessment Revisited—Status and Outlook.”The present article provides an update on progress toward alternative SPF methods. It also proposes a validation process for such methods with the goal of equivalating them to and revising the gold standard ISO 24444:2019. First, however, consider the challenge of finding alternative SPF methods.

The SPF In vivo test as described in the norm ISO 24444 is a relatively complex method and requires significant equipment and time to be executed. However, because human skin serves as the template and performance indicator, it directly connects with the application of sunscreens and potential biological damage to skin caused by UV.

Human skin and the processes that occur during sunscreen application are also complex and difficult to match by alternative templates or procedures. Therefore, it has taken quite some time to develop methods that could, for the vast variety of sunscreens made globally, consistently deliver comparable results.

Furthermore, the In vivo SPF procedure utilizes UV radiation and represents a burden to the test subjects. Therefore, alternative procedures should avoid this burden. Also, the very nature of human subjects intrinsically causes some variation in results. The desire is therefore to identify alternative methods with less variation that are more robust and agree well with in vivo SPF results.

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Published by Cosmetics & Toiletries, April 2020