Expose a person to sunlight, and odds are the UV rays will jump-start a pathway leading to an increase in skin pigmentation, i.e. tanning. However, some people simply don't tan. These people often, one may have noticed, have red hair. It's no coincidence-- there's a well-known association between fair skin, red hair, and a defective version of a gene called MC1R. Homozygotes for the defective allele don't tan, thus leading to a greater chance of UV damage and skin cancer.

Red-headed mice, it turns out, have similar problems with tanning (on their ears, which are apparently a great model for human skin). In a new paper, researchers have demonstrated the role of MC1R is the tanning pathway, and have also reinstated the tanning pathway to MC1R-deficient mice using a topical application of a drug. This is cool stuff, and implies that one day it could be possible for redheads to simply put on a cream before heading to, say, Florida. The researchers obviously thought the same thing:

To test whether forskolin treatment might protect against UV carcinogenesis, xeroderma-pigmentosum-complementation-group-C-deficient mice (Xpc-/-) were crossed to the fair-skinned Mc1re/e; K14-Scf (C57BL/6 background) mice and subjected to either forskolin-containing or vehicle-control topical treatments for four weeks, before daily exposure to 250 mJ cm-2 UV-B (along with continued topical treatments) for 20 weeks-a UV dose approximating 1-2 h of ambient midday sun exposure at sea level in Florida, during July.

That cosmetic companies will now come up with creams that allow you to tan more at a given UV dose seems a given.