Polymorphic light eruption. Prevention with sunscreen associated with dihydroxyacetone

Background. Topical sunscreens characterized by a high PF are effective in the prevention of polymorphic light eruption (PLE). Methods. In this study the effectiveness of a topical sunscreen (PF = 60 B; 12 A+IR) associated with a dihydroxyacetone 5% cream has been evaluated. Twenty female volunteers affected with PLE entered the study. The volunteers had carried out a phototest showing a positive reaction elicited only by consecutive days exposures to UVA. Test procedure: application one a day of the dihydroxyacetone 5% cream; application twice a day of the high PF sunscreen followed by the exposure to increasing doses of UVA (1(st) day 20 J/cm2; 2(nd) day 35 J/cm2; 3(rd) day 45 J/cm2; from the 4(th) day to 21(th) day 60 J/cm2). UVA daily dose was delivered in two irradiative session: half dose during the morning and half dose during the afternoon. Results. Results show that the isomorphous reaction appeared on the area irradiated with UVA without application of dihydroxyacetone cream and topical sunscreen after a mean UVA dosage of 181 J/cm2. On the opposite on the skin area treated with dihydroxyacetone cream and topical sunscreen no subject showed the isomorphous response. Conclusions. In conclusion this preliminary tests show that the association of dihydroxyacetone 5% cream and high PF topical sunscreen is able to prevent PLE.