32 SOFW-Journal | 134 | 7-2008 K. Jung°, S. Champ*, H. Flößer-Müller*, M. Seifert**, T. Herrling*** The Vital Consequences of Choosing the Right UV-filter for the Prevention of Free Radical Boosting in UV-irradiated Skin after the Application of Self Tanning Creams Part 2 Keywords: skin, self tanner, UV irradiation, free radical, ESR Spectroscopy, UV-filter SUN CARE SELF TANNER  Introduction The detrimental effect of self tanners like dihydroxyacetone (DHA) and erythrulose applied directly before UV exposition of the skin was discussed in detail in (1). Contrary to this article some publica- tions (2) refer to the UV protection of self tanner formulations. In particular they described the UVA protection effect of the self tanner dihydroxyacetone (DHA). They claimed that dihydroxyacetone pro- tects against long wave ultraviolet radi- ation (UVA) and visible light whereby DHA offers a moderate sun protection factor (SPF). Volunteers were treated with 20% DHA cream twice in three ar- eas on the volar forearm. Participants were then photo-tested with simulated sunlight in each area. Blue reflectance was used to measure the skin coloration caused by DHA in the test sites. DHA was found to offer a significant SPF of 3.0. Simultaneously Lloyd et al. (4) (2001) re- fer to the generation of free radicals in skin during the sunless Maillard reaction in mouse skin. The Maillard browning reaction between carbohydrates and amines is well known in food chemistry as part of an extensive series of reactions collectively called Mail- lard browning reaction or more general- ly the non enzymatic browning reaction (5-7). The initial stages of the reaction are quite complex, but the ultimate prod- ucts are brown polymers known collec- tively as melanoidins. I t is generally known that the Maillard reaction which is responsible for the sunless tanning is correlated with the generation of free radicals in the skin. The number of free radicals is dramatically increased by simul- taneous UV exposure and results in a strong decrease of the Radical Skin Protection Factor of RSF « 1.0. This decrease of the RSF is correlated with a reduction of the self protection time of the skin. A waiting time between DHA application and the beginning of the sun irradiation can prevent this boosting effect of free radicals and leads to normal RSF values of unpro- tected skin of RSF = 1.0. The general aim of this study was the prevention of the dramatic increase of generated free radicals in skin rather than the elimination of these free radicals by free radical scavengers like antioxi- dants. That’s why this study concerns oneself with the application of DHA creams containing UV filters resulting in values of RSF > 1.0. Four filters: two UVB filters, one UVAB filter and a UVA filter were tested corresponding to their protection against DHA induced and UV boosted free radicals in skin. The radical protection realized by these UV filters extends over a wide range corresponding to the concentration and residence time of DHA inclu- sive the used UV dose. RSF values from RSF = 0.56 for the application of a UVB filter with a residence time of 20 min at 2 MED up to an RSF = 11.8 for a UVA filter were measured under the same conditions. The prolongation of the time between DHA application and sun exposure at 4 hours resulted in a further increase of the radical protection factor onto an RSF = 24.3.The determination of the waiting time inclusive of the radical protection factor are essential parameters characterizing self tanning creams. Abstract