What Does SPF Mean Anyway?
The SPF, or Sun Protection Factor, is a laboratory-based measure of the skin damage caused by UVB with sunscreen use relative to without protection. As with most theoretical measures, the empirical results don’t match up. Many variables affect the performance of sunscreen, including skin type, activity (particularly sports and water activity), application quality and reapplication frequency, amount absorbed by the skin, and the degradation of active ingredients by UV. Few people use enough sunscreen to benefit from the SPF protection promised on the label. Studies show that people typically use about a quarter of the recommended amount. Because sunscreen effectiveness drops off precipitously when under-applied, in everyday practice a product labeled SPF 100 actually performs like SPF 3.2, an SPF 30 rating equates to a 2.3 and SPF 15 translates to 2. Moreover, FDA scientists say SPF claims above 50 cannot be reliably substantiated. Carcinogens and Hormone Disruptors In Your Sunscreen? S
