How does a self-tanner work?

In a self-tanning product, DHA or dihydroxyacetone, often combined with erythrulose, are the molecules responsible for the artificial colouring of the skin.

Belonging to the family of sugars (oses), these molecules produce the desired effect through the phenomenon of non-enzymatic browning known as Maillard reaction. 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 (corneocytes) to form pigments, the melanoidins, or brown chromophores.

The twenty amino acids react differently to DHA, producing various shades of colouration ranging from yellow to brown. It has also been demonstrated that lysine, glycine, and histidine react very quickly with DHA. The resulting colouration is similar to that of melanin, the natural substance found in the deeper layers of the skin. However, the mechanism of this artificial tanning is entirely different from natural tanning, which is based on the increased production of melanin following exposure to ultraviolet rays.

The artificial browning effect on the skin due to the use of a self-tanning product is therefore a result of this superficial reaction. This reaction only occurs at the level of the stratum corneum and poses no danger to the skin or general health, unlike UV rays from the sun. Interestingly, this reaction is similar to what happens in cooking, for example when a chicken roasts in the oven and browns.

Skin pigmentation appears within 2 to 6 hours following the application of the self-tanning product. However, this colour gradually fades to completely disappear in 5 to 7 days. This phenomenon is explained by the frequent renewal of the stratum corneum (natural exfoliation process).

It is crucial to remember thata self-tanner does not in any way protect against the effects of the sun's UV rays, especially if it does not contain sun filters. Indeed,having a tanned complexion after using a self-tanner does not equate to sun protection. That's why it is essential to apply abroad-spectrum sunscreen during exposure.

Self-tanningproductsmay also contain other ingredients such asantioxidants(vitamin E, etc...) which protect the skin against free radicals responsible for skin ageing and cellular damage, or eventanning activating moleculesthat stimulate the skin's natural melanin production likecarob pulp extract,buriti oil, etc... thus ensuring an even distribution and a more natural tan.

Thedihydroxyacetone(DHA) is a monomer of carbohydrate 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.

Note : Even though these two molecules act in the same way on skin cells, they do not have the same reaction 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.