015 Two broadspectrum SPF 15 sunscreens offer different protection against UV induced depression of delayed type hypersensitivity response in humans

Abstract

Sunscreens are designed to protect against sunburn and their efficacy is indicated by the so-called sun protection factor (SPF). However this index may be inadequate to provide a relevant measurement of protection against other biological damages induced by UV such as immunosuppression. We measured in human volunteers the ability of two broad spectrum SPF 15 sunscreens, with different UVA protection levels, to prevent the fall in local delayed type hypersensitivity (DTH) response to recall antigens (Multitest Pasteur/Merieux) after acute solar simulated UV exposure. We first determined the UVR-dose needed to induce a significant reduction of DTH response in different groups of 15 volunteers. Two minimal erythernal dose (MED) were found to be the minimal immunosuppressive dose. This dose induced a 36% average fall in immune DTH response. The lower doses tested (0.5 and 1 MED) were ineffective. Sunscreen treated groups were exposed to a dose equal to 2 MED × SPF of the products. The DTH response was not lowered in the group treated by the product having the highest UVA protection. Conversely the DTH response was significantly reduced by 55.7% in the group treated with the low UVA protection sunscreen. These data suggest that sun protection factor may not be sufficient to predict the ability of sunscreens to protect the immune system. A measurement of UVA protection may also be necessary as UVA seems to have a low contribution to erythema but strongly affects immune response.