Skin damage due to exposure to ultraviolet light can result in skin cancer, premature aging of the skin, damaging free radical production, wrinkles, and saggy skin. These consequences can result from both direct sunlight exposure and from artificial sunlight, such as tanning beds. Fortunately, many people are using sunless self-tanning products to obtain their desired “golden glow”. These sunless tanners come in lotions, sprays, gels, wipes, and powders.
Most topical self-tanning products contain bronzers, which coat the skin with color, and/or dyhidroxyacetone (DHA), a chemical that causes darkening within the skin. Bronzers can be washed off immediately with soap and water, while DHA is resistant to normal soap, water, and sweat and triggers a series of chemical reactions within the skin in a matter of a few hours. DHA is a sugar-based molecule that comes from plants and has been used for over 50 years to achieve a “safe” tan. People who suffer from a skin disease called vitiligo have loss of pigment-producing skin cells, and sunless tanning products have been used to create temporary color to mask areas of vitiliginous skin.
Science of DHA
DHA applied to the skin reacts with amino acids in the epidermis, particularly the outermost layer called the stratum corneum. After 2-4 hours of reactions in the skin, pigments similar to melanin called melanoidins are produced. This series of reactions is similar to the Maillard reaction, which occurs in the browning of foods such as meats.5 DHA reacts with amino acids such as histidine, glycine, and lysine within the epidermis to cause temporary pigmentation. Studies have demonstrated that pigments induced by topical DHA do not concentrate in deeper skin layers, staying mainly in the outermost stratum corneum. The pH of the skin (which measures the amount of acidity), is normally between 4-5. Studies have found that raising the pH of the skin to 7 (making the skin less acidic) when DHA is applied leads to greater pigmentation. DHA concentration in tanning products ranges from 1-15%, with higher numbers resulting in more intense color.
Sun Protection from Spray Tanning
Studies have demonstrated that skin pigmentation induced by DHA may be moderately protective against ultraviolet type A (UVA) only, but not ultraviolet type B rays (UVB).[8,9] The protection can be increased with each additional layer of DHA product, however, with directed usage of these products, they are not considered to be protective from sun damage and sunscreen should still be worn.
The FDA requires that all sun-tanning products formulated without sunscreen carry the below warning sentence on the product label:
“Warning – the product does not contain a sunscreen and does not protect against sunburn. Repeated exposure of unprotected skin while tanning may increase the risk of skin aging, skin cancer, and other harmful effects to the skin even if you do not burn.” (21 CFR 740.19)
Safety of Spray Tanning
One study using mouse skin implicated that free radicals (which are reactive and damaging molecules) are produced in the reactions that occur when DHA is applied to the skin. A later study concluded that 180% more reactive oxidizing species (ROS) are produced after 40 minutes of sun exposure in DHA-treated skin, than in skin with no topical DHA. According to this study, the most intense production of free radicals occurred during the first 15 minutes of sun exposure. It would be prudent to refrain from sun exposure on the day of sunless tanning to reduce the potential for ROS generation. Further research is needed to better understand the timeline for how sun-induced ROS generation changes with time after a sunless tan.
One study found that sunless tanning spray with DHA of 9% decreased Vitamin D production. People with low vitamin D who are concerned should discuss supplementation with oral vitamin D with their medical providers.
According to the Skin Cancer Foundation, “there is no clear evidence that DHA is harmful to humans if applied topically and used as directed.”
The Food and Drug Administration (FDA) has approved the use of DHA-containing sunless tanning products for use “applied only to external parts of the body and not to the lips or any body surface covered by mucous membrane” (21 CFR 70.3v). It is important to note that DHA has not been approved by the FDA for the use in “tanning” booths, such as in spray or mist tans. If you choose to receive tan via the spray or mist methods, the FDA advises covering your entire eye area and mouth area including lips to prevent ingestion or inhalation.