Dihydroxyacetone-induced pigmentation: Dihydroxyacetone (DHA), a three-carbon sugar, is the browning ingredient in commercial sunless tanning formulations. DHA preparations have been used for more than 50 years and are currently popular for producing a temporary pigmentation resembling an ultraviolet-induced tan. Pigmentation develops over a period of hours after application of DHA and remains for several days.
Similar to melanin, DHA-induced pigmentation absorbs light throughout the visible spectrum; however DHA pigment is much less photoprotective than melanin against UV radiation because it has lower absorption in the UV range. DHA pigment is also only moderately protective against UVA radiation. Multiple applications of DHA have been shown to induce pigmentation that is suffi cient to protect uninvolved skin during psoralen plus UVA (PUVA) therapy for psoriasis, which allows higher UVA doses to be used resulting in fewer treatments than standard PUVA regimens. In addition, pigmentation of vitiligenous skin using DHA has been reported to produce a cosmetically acceptable result.
DHA-induced pigmentation forms in the stratum corneum, rather than in deeper epidermal layers, as demonstrated by removal of the pigmented layer by tape stripping.6 The chemistry leading to DHA pigments is believed to be similar to that established for reaction of other sugars with compounds containing amino groups (Maillard reaction).