Linear and exponential sunscreen behaviours as an explanation for observed discrepancies in sun protection factor testing.
Carles TrullasCorinne GrangerHenry W LimJean KrutmannPhilippe MassonPublished in: Photodermatology, photoimmunology & photomedicine (2019)
Differences in reported SPF values depend on the linear vs exponential behaviour of such products if subjected to low- vs high-dose test regimens. Under real-time exposure to natural sunlight, exponential and linear sunscreens did not differ in their erythema prevention capacity. Laboratory SPF testing of exponential sunscreens bears the risk of underestimating their in-use SPF.