Sunless tanning: hydroxyacetone


Sunless tanning is possible with the help of the chemical hydroxyacetone, which is the active ingredient in self-tanning creams.

When food is cooked or exposed to enzymes, it acquires our beloved golden color, this is due to the Maillard reaction, in which carbohydrates interact with proteins. The outer layer of the skin is mostly composed of proteins, which, like food proteins, can react with carbohydrates to form brown products. The chemical that makes this process possible is called dihydroxyacetone (DHA). DHA is a white powder with a sweet taste. Apply its solution to the skin, and you will get a quick and even tan. However, the first DHA-based products gave the skin not a uniform, but a spotted color, which looked even worse than pale skin, the unfortunate had to walk for a long time with spots, since they could not be washed off, it was necessary to wait several weeks until the upper layers of the epidermis came off .

The use of dihydroxyacetone as a fake tan was first proposed in the mid-1950s at the Children’s Clinic of the University of Cincinnati. Eva Wittgenstein worked there with sick children whose bodies could not fully store glycogen — one of the key carbohydrates in the human body, responsible for the rapid supply of glucose to tissues. The researcher believed that such a pathology could be combated with large doses of DHA. This substance is synthesized in plants and animals, being an intermediate product of carbohydrate metabolism. It is absorbed even faster than glucose. Unfortunately, after taking a dose of dihydroxyacetone, some children vomited, and then it was noticed that if DHA got into the skin, brown spots appeared on it after a few hours. Wittgenstein became interested in this and decided to experiment on herself. She applied a solution of dihydroxyacetone to her skin and saw that it actually turned brown.

On an industrial scale, DHA is produced by the fermentation of glycerol (glycerol) in the presence of the microorganism Acetobactersuboxydans. The enzymes of this bacterium split off two hydrogen atoms from glycerol and convert it into DHA. DHA can bind to the free amino groups of proteins in the stratum corneum, causing the skin to turn brown after thirty minutes. The substances that are formed in this case are called melanoidins. Only the surface layer of the skin is involved in the formation of such a tan. There are many creams and lotions on the market today that contain 2 to 5 percent DHA. These products should be slightly acidic, which is achieved by adding phosphates, which give the solution buffer properties, its pH is 5. The best-known quick tanning lotions include Man-Tan, Oxatone, QT (Quick Tan) and Winter Tan. The disadvantage of DHA is that, despite the good solubility of the substance in water, the resulting solution tends to go into a gel form, which is unevenly applied to the skin, which causes uneven tanning.

This problem is solved with the help of additional ingredients that help the lotion retain its properties. Another way is to make DHA-based products in the form of creams. Some beauty salons use sprays with DHA, they are applied to the skin with a spray bottle.

Quick tanning products are not sunscreens, although they do have some protective effect by a factor of about two. Their main purpose is to allow people to get a golden skin color, and at the same time not be exposed to ultraviolet radiation. And for those who want to surprise everyone on the beach with a ready-made tan, while still being protected from the sun, there are blends that include both DHA and titanium dioxide, their protection factor varies from 15 to 30.

Source: based on materials from John Emsley’s book «On the benefits and harms of the products we love to buy»

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