Applying caffeine directly to the skin may eventually prove to help prevent sunlight-induced skin cancer, suggest the findings from a recent mouse study.

Caffeinated beverage intake has been linked with significant reductions in skin cancer as well as several other types of cancer—most prominently hepatocellular and endometrial cancers—for reasons not yet known. In earlier research, mice that were fed caffeinated water and exposed to lamps generating ultraviolet B (UVB) radiation were able to kill off cells badly damaged by the UV rays, reducing their cancer risk.

A new project strengthens the theory that caffeine guards against certain skin cancers at the molecular level by inhibiting ATR, a protein enzyme in the skin. 

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“Although it is known that coffee drinking is associated with a decreased risk of nonmelanoma skin cancer, there now needs to be studies to determine whether topical caffeine inhibits sunlight-induced skin cancer,” explained Allan H. Conney, director of the Susan Lehman Cullman Laboratory for Cancer Research at Rutgers, The State University of New Jersey (Piscataway), in a statement describing his team’s findings.

As Conney and colleagues reported in Proceedings of the National Academy of Sciences in the United States of America (2011; 108[33]:13716-13721,, instead of inhibiting ATR with caffeinated water, the investigators genetically modified and diminished ATR in one group of mice. These mice developed 69% fewer tumors and four times fewer invasive tumors than mice with normal ATR, and the tumors developed more slowly. But when both sets of mice were exposed to chronic UV rays for an extended period of time, both developed tumors. According to Conney, this indicates that ATR inhibition works best at the precancerous stage.

“Combined with the extensive epidemiologic data linking caffeine intake with decreased skin cancer development, these findings suggest the possibility that topical caffeine application could be useful in preventing UV-induced skin cancers,” concluded Conney and associates, who added that topical caffeine directly absorbs UV and thus also acts as a sunscreen. “This chemopreventive approach via ATR inhibition might be especially beneficial for individuals at high risk of UV-associated nonmelanoma skin cancers.”