A natural tan, achieved through the combination of dihydroxyacetone (DHA) and erythrulose.

Thedihydroxyacetone(DHA) is a carbohydrate monomer with the empirical formula C3H6O3. This molecule can be of synthetic or plant origin. Natural dihydroxyacetone is typically derived from abiotechnological processthat involves the stages of fermentation and bacterial bioconversion of glycerol extracted from plants such as rapeseed, corn, or beetroot.

DHA is currently the main active ingredient in self-tanning products.However, in the 1960s, this compound was not favoured due to the unnatural orange hue and streaky demarcations it left on the skin. It only became popular in the 1980s because when combined with erythrulose, it then provides a much more even and natural sun-kissed complexion. Erythrulose is also a compound obtained through biotechnology. This natural sugar is present in plant cells, such as raspberries or beetroot in particular.

The combination of these two compounds thus promotes a natural tan. Furthermore, erythrulose has moisturising properties that counterbalance the drying effect of DHA.

When applied to the skin, these tanning agents react with the amine functions carried by the amino acids present in the dead cells of the corneal layer to form pigments, known as melanoidins. The browning effect on the skin results from this reaction, known as the Maillard reaction. The pigmentation of the skin appears within 2 to 6 hours following the application of the self-tanning product. However, this colour gradually fades to disappear completely in 5 to 7 days. This phenomenon is explained by the frequent renewal of the corneal layer (a natural process of desquamation).

Note : Even though these two molecules act in the same way on skin cells, they do not react at the same speed. Thus, DHA rapidly colours the skin while erythrulose acts slowly and progressively. It is also this balance between the reaction times of the two compounds that promotes a natural tan.