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Mice are not men. But the unexpected finding that four commonly used moisturizers promoted skin cancers in mice suggests that these--and perhaps other products--may not be as safe as they're thought to be.
The moisturizers tested in the study were Dermabase, Dermovan (a wholesale-only product discontinued in 2006), Eucerin Original Moisturizing Cream, and Vanicream.
In a mouse model of sun-related skin cancer, frequent application of each product resulted in more skin tumors and faster tumor growth, says study leader Allan H. Conney, PhD, director of the Susan Lehman Cullman Laboratory for Cancer Research and professor in the school of pharmacy at Rutgers University in Piscataway, NJ. "This was unexpected. We really did not expect to see the tumor-promoting activity of these creams," he said.
In fact, Conney and colleagues were getting ready to use one of these moisturizers--Dermabase--in human clinical trials of topical caffeine, which prevents skin cancer in animal studies. "We thought it would be prudent to test Dermabase by itself to see if it had tumor-promoting activity," Conney said. "We did not think it would. But lo and behold, to our surprise we got an increased rate of skin cancer."
This led to new tests of Dermabase and the three other moisturizers, which the Conney team hoped to use in their human study. For these new animal studies, the researchers used hairless mice irradiated with ultraviolet light twice a week for 20 weeks. With no further irradiation, such mice eventually develop skin cancer, very much like humans overexposed to sunlight early in life.