The various self-tanning substances used for a sun-kissed complexion without sun exposure.

Melanoidins should not be confused with melanin. The former are artificial polymeric pigments formed in the stratum corneum, while the latter are natural epidermal polymeric pigments produced during the melanogenesis process.

It's important to note that the more corneocytes (skin cells) present, the more intense the brown coloration, hence the appearance of sometimes darker areas on the thicker parts of the skin, such as the knees, elbows, or heels. This is why it is generally recommended to exfoliate before using a self-tanner. DHA allows for a tanned complexion in about six hours. The intensity of the coloration increases proportionally with the concentration of DHA, the temperature, and the pH of the skin and the product, with an alkaline environment promoting the Maillard reaction. The browning then gradually disappears as the cells of the horny layer renew themselves.

Troxerutin is a semi-synthetic flavonoid derived from rutin, a natural polyphenol found in certain plants such as eucalyptus, or hawthorn. It is primarily used in pharmacology for its vasoprotective effects in the treatment of venous insufficiency, but it also has relevance in cosmetics when it is combined with dihydroxyacetone. Indeed, although the application of troxerutin alone does not generate any coloration, its combination with DHA helps to intensify and stabilize the tanning effect.

Furthermore, at a concentration of 3%, troxerutin also possesses antioxidant and anti-inflammatory properties. Indeed, it is capable of trapping free radicals due to its chemical structure rich in double bonds, as well as inhibiting the release of certain pro-inflammatory cytokines. Thus, troxerutin promotes the maintenance of the integrity of the skin barrier function and the achievement of a uniform and luminous complexion.

Less known to consumers than DHA and erythrulose, troxerutin has also been less studied as a self-tanning molecule, which explains its more limited use in products of this type.

The Isochrysis galbana is a unicellular microalgae primarily cultivated for aquaculture. However, it is also considered by the cosmetic industry for its self-tanning properties, which are derived from its richness in dihydroxyacetone. The addition of Isochrysis galbana extracts in self-tanners could indeed increase the concentration of DHA, thereby optimizing the coloring effect. However, to confirm its effectiveness and safety in this context, scientific studies are necessary.

On the other hand, recent studies have suggested that extracts of Isochrysis galbana could play a role as a skin pigmentation accelerator. They contain pheophorbides, which are chlorophyll degradation products, possessing photosensitizing properties. Theoretically, these compounds could promote faster tanning under the effect of UV rays. However, the use of photosensitizing substances is not without risk. These molecules not only promote skin tanning, but also increase the risk of sunburn, hyperpigmentation, and even skin cancer. Furthermore, this approach deviates from the principle of self-tanners, which aim to induce tanning without sun exposure.