What it is
Dihydroxyacetone is a simple ketose sugar that develops a tan-like color through the Maillard reaction with amino acids in the outermost skin layer, producing brown melanoidin pigments. The color appears over several hours and gradually fades as those surface cells shed. In sunscreen products it is included to provide an immediate cosmetic bronze tint rather than to contribute UV protection.
Safety & warnings
DHA is generally well tolerated on intact skin and the color reaction is confined to the surface layer. The resulting color does not provide meaningful protection from ultraviolet light. Inhalation of sprayed product is not intended, so application in mist form should avoid the eyes, lips, and mucous membranes.
Origin & sourcing
Dihydroxyacetone is produced synthetically, typically by fermentation of glycerin or by other industrial routes; it occurs naturally as an intermediate in carbohydrate metabolism.
History
Its skin-coloring effect was identified in the mid-twentieth century, and it became the standard active ingredient in sunless tanning products thereafter.
Questions everyone asks
Does dihydroxyacetone protect skin from the sun?
No. It only adds a temporary surface color; any sun protection in a product comes from its UV filters, not from DHA.
How long does the color from DHA last?
The tint develops over a few hours and typically fades within several days as surface skin cells naturally shed.