A while back I got a question regarding the health implications of sunless tanners, I've been meaning to have a look into it since then, but somehow kept pushing it away, until the question came up again yesterday. Also, it is Spring (despite the still cold weather in Europe), and the time for self-tanning is fast approaching.
Let's have a look then, shall we?
Most topical sunless tanners contain dihydroxyacetone (DHA) as the active ingredient. DHA is not a dye, stain or paint, but causes a chemical reaction with the proteins of the upper-most layer of the skin (stratum corneum). It does not involve skin pigmentation nor does it require exposure to ultraviolet light to initiate the color change. The effect is temporary and fades after 3-10 days.
DHA has been approved by the FDA for use as a tanner since 1977, and has typically been used in fake-tan lotions and creams. Its use is restricted to external application, which means that it shouldn't be sprayed in or on the mouth, eyes, or nose, says Linda Katz, M.D., director of the FDA's Office of Cosmetics and Colors in the Center for Food Safety and Applied Nutrition. "DHA should not be inhaled, ingested, or used in such a way that the eyes and eye area are exposed to it because the risks, if any, are unknown," Katz says. For consumers who choose to get DHA spray in tanning booths, the FDA recommends protective measures for the eyes, nose, and mucous membranes.
It is also important to remember that the fake tan achieved by DHA containing products does not protect you from UV-rays, and actually, one study ( Katinka Jung of the Gematria Test Lab in Berlin- 2007), showed that pig- skin treated with 20% DHA for forty minutes had 180% additional free radicals formed during sun exposure compared with untreated skin. Although it is unclear what layer of skin (dermis or epidermis) these free radicals were present in, it may be prudent to take extra care in avoiding sun exposure or using sunscreen for a period of time (duration unknown) after application. An antioxidant cream might also minimize free radical production.
The study by Jung et al. also found that dihydroxyacetone has an negative effect on the amino acids and nucleic acids of the skin. The free radicals are due to the generation of AGE (Advanced Glycation Products- mentioned in my post about sugar, and exercise) as a result of the reaction of DHA with the skin.
Many self tanners use chemical fragrances which may cause skin allergies or may trigger asthma. Furthermore, some of them contain parabens (read more about skin and parabens here).
Summed up, there are reason to take specific precautions when using a self tanner, such as amping up the solar-protective regimen, including limiting sun exposure after DHA application, and adding an antioxidant containing cream. Otherwise, DHA is still the safest way to get a tan. I should however mention; there are questions being raised in the medical community regarding DHA's effect and safety when inhaled (such as during a spray-tan-booth-session), but more research is needed before any conclusions on that matter can be drawn. Until then make sure to wear adequate protective goggles, and/or a facial mask (alternatively, hold you breath when you can).
Jung K, Seifert M, Herrling T, Fuchs J. UV-generated free radicals (FR) in skin: their prevention by sunscreens and their induction by self-tanning agents. Spectrochim Acta A Mol Biomol Spectrosc. 2008 May;69(5):1423-8.
Benamar N, Laplante AF, Lahjomri F, Leblanc RM (Oct 2004). "Modulated photoacoustic spectroscopy study of an artificial tanning on human skin induced by dihydroxyacetone". Physiological Measurement 25 (5): 1199–210.