COSMETICS AND BATHROOM PRODUCTS:SUNLESS TANNING PRODUCTS.

SUNLESS TANNING PRODUCTS

While Greco-Roman, Elizabethan, and early American colonial societies viewed individuals with pale skin as belonging to the upper classes, in the twentieth century society began accepting bronzed skin. The suntan became the symbol of wealth and leisure, and brown- and beige-tinted powders and creams were created and brushed on the skin to supplement natural sun tanning. Although there is currently an increasing awareness of the detrimental effects of solar irradiation on human skin, a tanned appearance remains in fashion.

To achieve a darker tanned appearance without sun exposure, various sunless tanning formulations have become available over the counter. Most self-tanning products (e.g., lotions, foams, and sprays) contain the tanning agent dihydroxyacetone (DHA; C3H6O3) as an active ingredient. Discovered as a skin darkener in the 1920s and first marketed as a tanning product ingredient in the 1960s, this carbohydrate can be de- rived from a vegetable source such as beets or sugarcane or produced commercially from glycerine using a bacterium that converts alcohol into acetic acid. The sunless tan created by applying the FDA-approved DHA cosmetic ingredient to the skin is artificial because no melanin is involved in the process. The action of DHA is limited to the upper layer of the epidermis (stratum corneum) and involves a reaction between DHA and skin proteins. In general, the Maillard browning reaction (also known as “nonenzymatic browning”) between carbohydrates and amines is part of an extensive series of reactions that is the basis for the brown color caused by DHA. While the initial stages of the reaction are quite com- plex, the chemical reaction between DHA and amine groups of specific protein amino acids (e.g., arginine, lysine, and histidine) within the stra- tum corneum eventually yields brown polymers collectively known as melanoidins, large cross-linked molecules. The development of brown color usually requires two to four hours after application, and the color intensity is dependent on the formulation concentration of DHA in the product. Melanoidins are quite stable, so the sunless tan usually lasts be- tween five and seven days from the initial application. However, the epidermis is quite regenerative and is completely replaced every thirty-five to forty-five days, so product reapplication is recommended to maintain the tanning effect. When used alone, DHA can cause dryness and create an uneven, orange/yellow, unnatural-appearing tan. Some products contain erythrulose, a natural ketose obtained by biofermentation, that is often applied in an emulsion in combination with DHA and leads to a more uniform, streakless tanning of the skin and longer-lasting tanning color. Tanning color tonality may also be affected by adding red coloring agents to the sunless tanning product, including iron oxides, D&C pig- ments, caramel, and carmine. In addition, other products added to sunless tanning products include water, emollients (e.g., cetyl alcohol, cyclo- pentasiloxane, cetyl palmitate, mineral oil, palm kernel oil, C12-15 alkyl benzoate), emulsifiers (e.g., cetyl hydroxyethylcellulose, polysorbate 60, steareth-20, inositol, polyquaternium-37), humectants (e.g., propylene glycol, glycerin, sorbitol), moisturizers (e.g., lanolin, cocoa butter, herbal extracts, lactic acid, xanthan gum, methylpropanediol), vitamins (e.g., tocopheryl acetate [vitamin E acetate], panthenol [provitamin A], tocopherol [vitamin E], panthenol [provitamin B5]), lubricants (e.g., dimethicone copolyol), texturizers and fillers (e.g., mica, glyceryl stearate, magnesium aluminum silicate), solvents (e.g., benzyl alcohol, stearyl alcohol), buffers (e.g., disodium EDTA), fragrance, alkalizers (e.g., sodium citrate, sodium hydroxide), and preservatives (e.g., BHT, sodium chloride, sodium meta- bisulfite, methylparaben, propylparaben, butylparaben). Active ingredients such as octocrylene, octyl methoxycinnamate, oxybenzone, or lawsone (the active component of henna; provides red-orange tint) may be added to provide sunscreen protection, since sunless tanning products alone do not provide skin protection against UV radiation similar to a melanin- based tan.

Although cosmetic bronzers can also yield a sunless tan with relatively immediate results (usually within forty-five to sixty minutes), these products, in the form of powders, creams, foams, and lotions, are essentially a form of brown-tinted makeup that can easily be removed with soap and water.