Scientists have created a tanning drug that makes human skin darken without exposure to sunlight or the intense UV of a tanning bed. Instead, the drug alters gene regulation in skin cells to give their pigment production a boost.

So instead of just rubbing on sun cream, pale people could rub on a drug a couple of days before hitting the beach. That's the hope of a team of scientists who have published a breakthrough study in the journal Cell Reports on a topically applied drug that creates a 'real' fake tan in human skin.

The team tested it on red-furred mice as well as human skin in a dish. The mice turned almost completely black after just a couple of days, if they were given a very big dose of the drug.

After a few days, the tan began to fade as dead skin cells were replaced with new ones. On the human skin, the tans also lasted for days.

Preventing skin cancer?

It might be seen as good news for redheads and other people, such as Donald Trump, who frequently hit the bottle to get a bronzed glow. But the main intention is to protect the most at-risk from skin cancer.

"We believe it's really turning on the actual pigment pathway," study author David Fisher of MGH and Harvard Medical School told IBTimes UK. "It's the equivalent of the tanning response."

It's not been a straightforward process. One of the big hurdles in creating the drug was to find a molecule that could penetrate the skin. The team had previously made a compound called 'forskolin' in 2006 that did a similar job in mice, but human skin is a lot tougher.

"There are no rules for what will penetrate human skin or not. It's a very poorly understood field. We tried to design molecules that were a bit smaller and had less charge, so more likely to be absorbed," Fisher said.

Unlike forskolin, derived from the mint plant, this tanning drug is not a natural product. Many natural compounds are large and charged, making it very hard for them to penetrate the skin.

"In the future it would be interesting to try to identify natural compounds, although this could be challenging," Fisher admitted.

Tanning drug
Human skin in the lab that had been treated with the tanning drug (right). The square in the middle had received no treatment, and the square on the left was treated with a control substance. Nisma Mujahid and David E. Fisher, MD, PhD, Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital

Altering gene expression

The new drug targets a different part of the cell's machinery to forskolin, but achieves the same effect – creating more of the dark proteins that influence skin colour. It works by inhibiting the Salt Inducible Kinase system. Putting the brakes on this in turn stimulates the genes that result in pigmentation.

If the drug is not specific enough and binds to other kinase enzymes that impact things besides skin pigments, it could have unwanted side effects, said Dorothy Bennett, director of the molecular and clinical sciences research institute at St George's University of London, who was not involved with the research.

"Other kinases besides the target have been fully inhibited at high concentrations," Bennett said. "If that concentration were to get through the skin, those kinases would be inhibited by the molecule."

Some of these enzymes play an important role in cell division. Inhibiting them could have an effect on the way cells in the body divide.

Redheads
Redheads and other people with very pale skin are at the greatest risk of skin cancer caused by UV damage. Eddy Van 3000 / Flickr

But Fisher said that none of the mice involved in the study suffered any visible adverse effects.

"At this stage we have not seen any side effects or red flags," he said. "In the next stages, we see a toxicity study as paramount. That is a top priority at this point."

Reaching certainty that the drug doesn't have any toxicity for humans will be the big hurdle for the drug, and it will be several years before it enters clinical trials in humans.

If the drug does pass these tests with no big drawbacks, it could be a very promising development, Bennett said.

"You might be able to reduce the risk of skin cancer," she said. "Instead of lying under UV lamps or sunbathing to get a tan, this drug – if it isn't toxic – could give you a tan without having to do that. You could do it with a chemical instead."