DHA & AA:

According to the American Academy of Dermatology, the most effective sunless tanning products contain dihydroxyacetone (DHA) as the active ingredient. DHA is a colorless chemical (it is derived from glycerin) that interacts with the amino acids in dead skin cells to produce a brown color change. Since these dead skin cells are constantly being shed, the color change produced by DHA usually lasts about five to seven days.

AA is a long chained polyunsaturated fatty acid in the omega-6 family.It is the brain's principal omega-6 fatty acid and is often too high in modern diets. ALA , EPA, and DHA can counter the effects of AA.