THURSDAY, Aug. 14 (HealthDay News) -- Common moisturizing creams helped skin cancers spread and tumors grow in mice exposed to UV radiation, researchers at Rutgers University reported Thursday.

"These creams we tested have tumorigenic [tumor-causing capability] activities," said lead researcher Allan H. Conney, from the university's Susan Lehman Cullman Laboratory for Cancer Research.

But, he added, "I need to emphasize that what we have done is only in mice. We don't know what the implications are for humans. But it does raise a red flag that this is something that should be considered."

The report is published in the Aug. 14 issue of the Journal of Investigative Dermatology.

For the study, Conney's team exposed hairless mice to an extended period of UV radiation, which induced non-melanoma skin cancer. After stopping UV treatment, they applied four different common brands of skin moisturizers to the animals' skin five days a week for 17 weeks.

The researchers found that mice treated with skin moisturizers showed an increased rate of tumor formation. In addition, there were more tumors on the animals treated with moisturizers than on the mice that were only given UV radiation.

The moisturizers used were Dermabase, made by Patrick Laboratories in Minneapolis; Dermovan, made by Galderma Laboratory Inc. of Fort Worth, Texas; Eucerin Original Moisturizing Cream, made by Beiersdorf of Hamburg Germany; and Vanicream, made by Pharmaceutical Specialties Inc., in Rochester, Minn.

Conney's group identified several ingredients in the moisturizers that appear to enhance tumor growth.

"We took out a couple of ingredients and made a cream that turned out to be non-tumorigenic," Conney said. The resulting lotion did not increase cancer growth in mice exposed to UV radiation, the researchers found.

"We really don't know what ingredients in these creams are doing that," Conney said. "There is a need to have the various companies test their creams to see whether or not there is a problem."

Conney thinks that companies can modify their products to remove this effect. "I am sure there are creams on the market that do not have tumorigenic activities and some of them may have anti-tumorigenic activity," he said.

Dr. Robin Ashinoff, a clinical associate professor of dermatology at New York University School of Medicine in New York City, thinks the findings are interesting but she said they may not apply to humans.

Drugs that have been implicated in growth in animals in the past do not always have similar effects in humans, Ashinoff said.

"Certainly, the issue here is to protect yourself from that degree of continuous UVB-induced priming for skin cancer by practicing good sun protection and sunscreen use in the first place," she added.

"These moisturizing creams might act as an irritant or a promoter of skin cancer in mice skin, but extensive study is needed before we advise people that their commonly used moisturizers can cause skin cancer," Ashinoff said.