What is your take on sunless tanning? It has been advertised as a very safe option (compared to tanning beds and massive sun exposure), but I haven't been able to find any detailed report on the chemicals behind self tanning.
The most common formulas contain dihydroxyacetone (DHA) as the active ingredient. DHA is not a dye, stain or paint, but causes a chemical reaction with the amino acids in the dead layer on the skin surface, turning it darker. Some products use erythrulose combined with DHA. Erythrulose works identically to DHA on the skin surface, but develops more slowly. The two chemicals used together may produce a longer lasting sunless tan.
Many self tanners use chemical fragrances which may cause skin allergies or may trigger asthma. Furthermore, some of them contain parabens. Parabens are preservatives that can affect the endocrine system.
For the 24 hours after self-tanner (containing high DHA levels, ~5%) is applied, the skin is especially susceptible to free-radical damage from sunlight, according to a 2007 study led by Katinka Jung of the Gematria Test Lab in Berlin. Forty minutes after the researchers treated skin samples with high levels of DHA they found that more than 180 percent additional free radicals formed during sun exposure compared with untreated skin.
Sources: various, including wikipedia