Commonly referred to as DHA, dihydroxyacetone is a naturally occurring carbohydrate that consists of a combination of only carbon, hydrogen and oxygen. In plants like sugar beets and sugarcane, the carbohydrate is vital to supplying energy to the cells. Sometimes, DHA is called by its alternate name, glycerone.
When used in skin care products, dihydroxyacetone is often derived by isolating a compound known as glycerol from a plant that contains DHA. This can be done through a number of techniques. Once glycerol has been obtained, it is then mixed with oxygen by adding a chemical like hydrogen peroxide. This causes a reaction that frees the DHA molecules from the other materials contained in the glycerol. When isolated and kept at room temperature, DHA is a white powder that consists of tiny crystals. It dissolves easily in many different types of liquids, which makes it ideal for use in skin care products.
One of the first experimental uses for DHA was in the developing of x-rays used to diagnose medical conditions and injuries that affect the bones. In clinical trials of x-rays performed by scientists in Germany during the 1920s, it was observed that when DHA accidentally came in contact with the skin, it caused temporary darkening or discoloration.
This phenomenon was again observed during clinical trials of the 1950s, when American scientist Eva Wittgenstein experimented on the use of DHA as a drug to treat a rare metabolic disease in children. When the children in the trial touched the DHA, their skin became darker within a few hours. Curious about what she observed, Wittgenstein started to experiment by applying DHA to her own skin. It is because of her work and findings that DHA is now a common ingredient in the skin care industry.
As the German scientists and Wittgenstein observed, DHA does indeed have the potential to cause the skin to darken to a browner shade. The change in color occurs only in the outermost cells of the epidermis, the outer layer of the skin. The change in skin color occurs because DHA reacts with amino acids, the building blocks of the skin protein keratin, of which the skin tissue is primarily made. When DHA comes in contact with these amino acids, it combines with them and forms molecules called melanoidins.
The melanoidins produced from DHA and skin's amino acids can vary in shade from golden yellow to deep brown and change the color of the skin in the same way that the natural-skin pigment melanin does. Melanin is the substance responsible for causing the skin to darken or tan when it is exposed to ultraviolet rays.
Because melanoidins are similar to melanin, experts at the well-known sunscreen manufacturer Coppertone saw the potential for DHA to be used as an agent to tan the skin without the need to expose the skin to the sun. In the 1960s, the company released its first sunless tanning product, which used DHA as its active ingredient. Although this first sunless tanner was effective, it often left the skin looking orange.
Over the last three decades, improvements in the way that DHA is produced for use in skin care products has allowed for more realistic-looking results from sunless tanners that contain the ingredient. Sunless tanning agents that contain DHA now offer results that rival those possible from laying out in the sun or using a tanning bed, and the ingredient is used in sunless tanning formulas produced by many brands.
Typically, sunless tanning products that are available for sale directly to the public contain concentrations of DHA that range from 3 to 5 percent. Formulations used in spray-tanning and professional sunless tanning skin treatments may feature up to 15 percent DHA by volume. Normally, DHA-based sunless tanners take 2 to 4 hours to produce results, but the formation of the melanoidins can continue for up to 72 hours, meaning that the darkening may continue for up to 3 days. Since the color change only affects a thin layer of cells, the results of the sunless tanning remain visible only until those cells are shed through natural cellular turnover.