For years, body-builders and prom queens have been covering themselves with tanning creams that turn their skin orange and sticky. These bronzers, with names like Fake Bake and Heavenly Hottie merely dye the surface of the skin with chemicals—or even carrot extract.
In an article published in the Sept. 21 issue of Nature, researchers from the Dana-Farber Cancer Institute in Boston introduced what could amount to the perfect rub-on tan. A team, led by Harvard University pediatrician David E. Fisher, discovered a compound that essentially tricks skin cells into acting as though sun's rays are bombarding them with light. Though it has only been tested in mice, if the compound works in humans, it could create a tan that is visually and biologically indistinguishable from one earned in the sun.
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The process that results in a natural tan can be compared to a four-stage chemical relay race. When the sun's ultraviolet rays hit the layer of cells near the skin's surface, the cells respond by creating a hormone called MSH (for melanocyte stimulating hormone) that migrates into the layer of cells below it. This hormone then stimulates the production of a chemical messenger known as cyclic AMP. Cyclic AMP, in turn, switches on the production of melanin, the natural pigment that darkens skin, which moves to the skin's surface, creating the bronzed look.
Fisher and his team tested a compound called forskolin—an extract from an Indian plant that is commonly used in biology labs—to see whether it could jumpstart the body's tanning mechanism. In actuality, forskolin bypasses the first two legs of the relay race, inducing cells to release cyclic AMP and then more melanin. After several days of rubbing forskolin on fair-skinned, red-haired laboratory mice, the researchers noticed a drastic change in the rodents' appearances.
"To our amazement the mice started to turn really dark," Fisher said, "virtually jet black"
If forskolin works in humans, it could also help fair-skinned people—such as red heads, whose tanning machinery is basically broken—look tan without risking dangerous burns.
Spending hours in the sun or lying on a tanning bed dramatically increases the risk of skin cancer. This year, more than 60,000 people will get melanoma, the most fatal type of skin cancer, according to estimates by the American Cancer Society.
But Fisher and others caution that it is far from clear if his tan-in-a-can will work on humans. Even though there are fundamental similarities, the biology of human skin is different than that of mouse skin, which is thinner and covered with fur.
"How [this] relates to human skin is unclear," said John T. Seykora, a dermatopathologist at the University of Pennsylvania.
The results of the study are further complicated by the fact that forskolin's safety is still uncertain.
"It is not a compound without side effects," Seykora said. "They want something less toxic than forskolin—although whether that does exist we don't know. If it does exist [Fisher] will retire early."