Over the last twenty years or so, people have developed a growing awareness of the harmful effects of sun on the skin. Nevertheless many people would still like to look tanned. Out of this contradiction arose the category of self-tanning products. These are preparations that induce a skin coloration similar to the color resulting from exposure of the skin to UV light.
All such products on the market today contain dihydroxyacetone (DHA) as the active ingredient that produces the brown coloration of the skin. (Others, such as glyceraldehyde, 6-aldo-D-fructose, erythrulose and glucose, have been shown to induce skin coloration to a lesser extent.) Modern products have overcome the unpleasant smell and feel of the older ones.
A self-tanning product has been used here on one leg only, to illustrate its effectiveness. It provides a safe way of attaining the desired aesthetic effect of a sun-tan.
Through a series of reactions, DHA reacts with the skin's amino acids to create the brown-colored product that makes the skin look naturally tanned. This reaction is not immediate, and usually takes from two to three hours for the full development of color on the skin. Once the coloration has developed, it will remain and will resist washing, since it is part of the skin cells' amino acid structure. It does not provide any protection from UV light, however, and cannot be considered as a sunscreen.
The color gradually fades as the cells themselves are lost through the natural desquamation process. Depending on the number of stratum corneum cell layers that are colored through the reaction with DHA, it usually takes five or six days for the color to disappear completely.
Modern self-tanning products contain a high proportion of silicones, which improve their spreadability and thereby reduce the risk of streaking.
The use of self-tanning products is a reasonable alternative for the health-conscious consumer who is determined to look tanned but who has finally understood that lengthy exposure to the sun will result at best in the acceleration of the aging process, and at worst in skin cancer.