The invention relates to cosmetic formulations containing dihydroxy-acetone and a topical support in addition to one or several compounds selected from the compounds of formulae (Ia) and (Ib), the physiologically acceptable salts of compounds of formulae (Ia) and (Ib), and the stereoisomeric forms of formulae (Ia) and (Ib), wherein R1, R2, R3, R4 and n have the meanings cited in Claim 1. The cosmetic formulations are characterized in that the UV-A protective effect of dihydroxyacetone is increased.