Dihydroxyacetone (DHA) is a sugar molecule that reacts with free amino acids in the outermost layer of the skin. This reaction, also known as the Maillard reaction, causes a temporary browning of the stratum corneum. The discoloration develops gradually within a few hours after application. Because DHA works only in the stratum corneum, it has no effect on deeper skin layers. The color fades gradually through the natural renewal of the skin.