Its use as a tanning solution originates from raw sugar cane and fermentation of glycerine and comes in the form of a white powder.
The use of dihydroxyacetone in the cosmetics industry came about from one woman's devotion to treating children suffering from glycogen storage disorders. Eva Wittgenstein was using DHA as the treatment and noticed that on contact with the skin the concentrate produced brown spots. By preparing aqueous solutions of varying concentrations she was eventually able to produce a realistic pigment that matched her own skin.
The science part...the chemical makeup of dihydroxyacetone:
HO - CH2 - C - CH2 - OH
At present sunless tanning products contain dihydroxyacetone concentrations of up to 5%. The higher the concentration; the darker the tan that will follow. However it is only stable in pH conditions of between 4 and 6. Too alkali or too acidic results in brown compounds forming, reducing the solutions effectiveness as a tanner. Airbrush tanning solutions are therefore mixed to be at a pH level of 5, and stored at cool temperatures since prolonged heating above 37 C (98.6 F) further affect stability. These factors give solutions a shelf life of between 6 and 9 months.
Some companies are starting to add erythrulose in their formulas. Why you may ask? There have been very few allergic reactions linked to DHA, so companies are now trying to accommodate for that very small percentage. Essentially erythrulose is similar in composition to DHA, but it does not produce as deep and fast a tan. Combining the two has proved successful in that erythrulose takes longer (48hrs) to fully develop thus extending the duration of the tan. However this extra ingredient does knock up the cost of tanning solutions.