Erythrulose

A fermentation derived, natural (Ecocert approved) keto-sugar that works as a self-tanning active. It's claimed to lead to a deep, even and long-lasting tan without streaks and without causing skin dryness. 

Compared to the other self-tanning active, DHA, Erythrulose works slower (takes a few days to develop the color, while with DHA it's only a couple of hours) but it also lasts longer. The two self-tanning actives are usually combined to give you  fast but long lasting tans.