Researchers have found that several moisturizers are linked to an increased skin cancer risk in hairless mice, but caution that there's no reason for people to panic. Mouse skin is very different from human skin, they say, and the mice also developed a very curable type of cancer called squamous cell carcinoma, not the more lethal melanoma. Lead researcher Allan Conney says the team
discovered the risk while testing a theory that caffeine could prevent skin cancer. "We sort of got into this by accident," Conney said in a telephone interview. "We wanted a safe cream that we could put the caffeine into" [Reuters].
In the study, which was published in the Journal of Investigative Dermatology [subscription required], researchers primed the albino mice with prolonged exposure to ultraviolet light, as if they'd been sunbathing for far too long. All of the mice in the experiment grew skin tumors, but those mice that had also had the moisturizer slathered on their skin had more tumors and faster tumor growth.
The ingredients responsible for this effect remain a mystery, but two prime suspects are mineral oil, which has been shown to be tumorigenic in animal models, and sodium lauryl sulphate, a known irritant [New Scientist].
But experts say there's no reason for people to throw out their skin creams.
Jonathan Rees, professor of dermatology at Edinburgh University, said it would be "crazy" to stop using moisturisers on the basis of this study. Mice had a thin skin and lived in the dark, unlike humans whose bodies were designed for exposure to the sun.... "Many agents that cause skin cancer in mice do not do so in man - indeed some of these agents are used as therapies. It seems extraordinarily unlikely that the results have any clinical relevance" [The Guardian].