Skin creams cause tumors on mice, study shows

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Certain commonly available skin creams may cause skin tumors, at least in mice, and experts should be checking to see if they might cause growths in people as well, researchers reported on Thursday.

They found several creams caused skin cancer in the specially bred mice, which had been pre-treated with ultraviolet radiation.

The cancers are not melanoma, the deadliest kind of skin cancer, they stressed in their report in the Journal of Investigative Dermatology, but another type called squamous cell carcinoma. Such tumors are slow growing, highly treatable and only fatal if patients fail to have them removed.

Allan Conney and colleagues at Rutgers University in New Jersey said they 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."

They were testing specially bred albino mice, which are prone to develop skin cancer. The mice are pre-treated with ultraviolet radiation to simulate the effects of a human who has had heavy sun exposure in the past but then stopped -- something that may be happening in the population as people realize the risks of getting a tan.

Conney's team decided to test the creams first and found that all four they tested caused tumors to grow on the mice.

He said he does not know why, but suspects two ingredients -- mineral oil and sodium laurel sulfate.