Sun protection factor determination in vivo using a single exposure on sunscreen‐protected skin

BACKGROUND: Determining sunscreen sun protection factors (SPFs) in a cohort of volunteers, particularly on products designed to provide high levels of protection, can be time-consuming. The conventional approach is to administer to each subject a series of exposures (normally between five and seven) on their sunscreen-protected skin. METHOD: A method, based on Gaussian statistics, is proposed that requires just a single exposure on the sunscreen-protected skin in volunteers to arrive at a reliable estimate of the mean SPF of a test product. RESULTS/CONCLUSION: The method is shown to yield an estimate of a product's mean SPF that is comparable, or better, in accuracy to estimates obtained by conventional multi-exposure testing.