Ingredient that affects the color of skin and that is present in most self-tanners. Derived from sugar, it reacts with amino acids found in the top layers of skin to create a shade of brown; the effect takes place within two to six hours and it can build color depth with every reapplication. It has a long history of safe use when applied topically to skin, where it affects only the uppermost layers.  Dihydroxyacetone doesn’t pose a health risk to skin nor does it accelerate signs of aging.
- Fu J, Dusza S, Halpern A. Sunless tanning. J Am Acad Dermatol. 2004;50(5):706-13.