Bad news for those who apply cosmetic products to their skin in addition to sunscreen: it may decrease the SPF’s (Sun Protection Factor) effectiveness, found a new study. In the study, researchers tested the effectiveness of sunscreens when applied over other products such as moisturisers. Eighteen participants with layers of product on their skin were assessed before and after swimming to see if water exposure thinned UV protection as well. A UV spectroscope and the tape stripping method were used to measure the depth to which the products absorbed into the skin. This showed that when sunscreen was applied over other cosmetics, the UV protection factor and distribution of sunscreen were not compromised if the user stayed dry. (Psst…your Summer Sunscreen Secret). It also showed that water had weakened the sunscreen properties when applied over other products, suggesting that sunscreen should be applied to non-treated skin to achieve the labeled protection factor. Now check out how to Turn Sunscreen Into Massage Oil.