COMPARATIVE EFFICACY OF SUNSCREEN REAPPLICATION REGIMENS IN CHILDREN EXPOSED TO AMBIENT SUNLIGHT

Undercompliance with sunscreen reapplication recommendations is a prob able factor in suboptimal childhood ultraviolet radiation (UVR) protec tion. However, improving on the ability of sunscreens to absorb UVR wi thout requiring frequent reapplication is difficult because the models most frequently used to develop and evaluate photoprotectants have on ly a limited ability to incorporate behavioral and environmental varia bles that are primarily responsible for loss of sunscreen efficacy. He nce, the objective of the present work was to develop a method to eval uate the efficacy of various regimens of sunscreen reapplication in ch ildren, under conditions of unrestricted behavior and exposure to ambi ent sunlight. Ninety-eight children, ages 7-12, Fitzpatrick skin types I-III, were divided between two study groups. The majority were types I-II, and all types were approximately equally represented between th e groups. The children received single or multiple applications of a s un protection factor 25 sunscreen to preassigned lateral halves of the body and engaged in unrestricted activities throughout a 6- (group I) or 8-h (group II) period of sun exposure at a seaside location. The e nd measurement for these studies was incidence and severity of erythem a 18 to 22 h after peak UV exposure. The results obtained showed that 1 or 4 sunscreen applications yielded comparable erythema protection a fter a 6-hour sun exposure, totaling 13 minimal erythema doses (MED). However, after an 8-h, 21 MED exposure, incidence and severity of eryt hema was greater at body sites treated with 1 compared with 5 sunscree n applications. Since the studies were conducted at UVR levels that pr obably exceed recreational sun exposures for most individuals in the c ontinental United States, we conclude that the method described here o ffers a viable approach to test the ability of sunscreens to provide s unburn protection to children without the need for frequent reapplicat ion.