Coffee drinkers may have another reason to enjoy their daily brew.

A study in the Proceedings of the National Academy of Sciences says caffeine can cut the risk of developing skin cancer by killing damaged cells that could turn into tumors. The study says coffee could even be applied directly to the skin.

The researchers who carried out the experiments on mice say they are not sure what it is about caffeine that protects against non-melanoma skin cancer. They now plan more research to see how caffeine works on humans.

Non-melanoma is the most common form of skin cancer. It is almost always successfully treated when caught early.

Melanoma can spread to other parts of the body, but also can be successfully cured when treated early.