A Laboratory Method for Measuring the Water Resistance of Sunscreens

January 7, 2004 | Contact Author | By: Berislav Markovic, Donna Laura and Mark Rerek, International Specialty Products
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  • Keywords/Abstract

Keywords: in vitro testing | sunscreen | water resistance | model skin substitute

Abstract: A new laboratory in vitro method for the measurement of sunscreen water resistance uses spectrophotometric analysis of a model skin substitute before and after 80-minute immersion. It gives good correlation with the FDA’s 80-minute immersion SPF results (very water resistant). The method is especially good for screening new formulations or water-resistant technologies.

Normal summer activities put a great deal of stress upon sunscreen products, particularly water exposure through swimming and sweating. Most sunscreen products are therefore designed to be water resistant. Regulatory agencies around the world, including the US Food and Drug Administration (FDA) and the European Cosmetic, Toiletry and Perfumery Association (COLIPA), have defined protocols to assure consumers that a claim of water resistance has been substantiated. Although protocols differ around the world, they all require testing on a significant number of people, which makes the testing expensive and time-consuming. The sunscreen formulator and chemist need a rapid and cost-effective method to determine at least a comparative level of water resistance in the laboratory in order to determine project progress.