Consumers are aware that exposure to sun rays can induce skin cancer. Nevertheless, a radiant tanned skin remains to be the healthy look for most western people when the sunny days return. That's why the self tanning market is nowadays so successful. The most commonly used self tanning raw material remains to be dihydroxyacetone. Dihydroxyacetone (DHA) is the key ingredient to gain a tan-like appearance without sun exposure as it carries less health risks than any other available methods. It is also the only active ingredient approved by the US Food & Drug Administration (FDA) for sunless tanning. It is a colourless 3-carbon sugar (C3H6O3) that, when applied to the skin, causes a chemical reaction with amino acids on the surface cells of the skin, thus producing a darkening effect. DHA does not damage skin as it only affects the outermost cells of the epidermis (stratum corneum). The main source of DHA results from raw sugar cane fermentation with glycerine.
Some companies are starting to add erythrulose to their formulas. There have been very few allergic reactions linked to DHA, so companies are now trying to accommodate for this very small percentage. Essentially, erythrulose is similar in its composition to DHA, but it does not produce as deep and fast a tan. Combining the two has proved successful in that erythrulose takes longer (48hrs versus 1 to 4 hrs for DHA) to fully develop thus extending the duration of the tan. However this extra ingredient does knock up the cost of tanning solutions.
DHA is available as a white powder soluble in water and mixtures of water and ethanol. That's why formulations containing DHA are usually ones with an external aqueous phase such as gels, oil in water emulsions, or hydro-alcoholic solutions (as shown in the following examples).
DHA is a colourless powder, but usually self tanning formulations are coloured to provide the consumer with an immediate colour result. Such cosmetic products contain synthetic dyes (for example cochenille red or FD&C yellow 10), pigments or natural dyes, such as caramel, as in the formula launched by Lancôme under the name of Lancôme "Aqua Flash Bronzer".