Moisturizer hazard? Murine study links products to heightened risk of skin cancer

Key Points

National report - Skin moisturizers may be contributing to the increase in sunlight-induced nonmelanoma skin cancer in the United States, results of a murine study suggest, but researchers and dermatologists say further study is needed to determine if the findings translate to humans.

Investigators at Rutgers University tested four over-the-counter creams and found that all four, but not the control cream or water, increased formation of squamous cell and keratoacanthoma tumors, according to lead researcher Allan Conney, Ph.D., director of the laboratory for cancer research at Rutgers University School of Pharmacy.

The study was published in the Journal of Investigative Dermatology.

Researchers were seeking to establish the baseline effect of a vehicle to be used in developing a caffeine-based, post-sun exposure skincare product that might increase apoptosis in sunlight-damaged skin cells and reduce the risk of developing such cancers.

Researchers initially tested the product Dermabase (Paddock Laboratories).

"Caffeine went into Dermabase quite readily. We thought it would be prudent to just test Dermabase by itself to see if there was any effect in mice before doing studies in humans," Dr. Conney tells Dermatology Times.

"I was surprised when the numbers came back, and disappointed because that messed up our proposed study in humans," he says. "We didn't want to use Dermabase anymore, and we had to find something we would be able to do the caffeine studies with."

Dr. Conney took three other popular moisturizers - Dermovan (Healthpoint), Eucerin Original Moisturizing Cream (Beiersdorf) and Vanicream (Pharmaceutical Specialities) - off a pharmacy shelf to test.

At the same time, he began working with Johnson & Johnson to develop a customized cream that was lacking sodium lauryl sulfate and mineral oil, which had earlier been associated with tumor formation in mice.

The company and university have jointly patented the blend.

Investigators reran the same experiment using hairless SKH-1 mice, which are predisposed to developing skin tumors after exposure to UVB radiation. The animals were exposed to the equivalent of relatively low-level - not extreme - sun exposure for humans, twice a week for 20 weeks.

The UVB exposure was then stopped and the animals were treated with a "normal" dose of the moisturizers for 17 weeks. "The three other commercial creams were also tumorgenic, whereas the custom blend was not," Dr. Conney says.

Untreated animals that received a water control or received the custom-blend cream all had about the same rates of tumor formation. In comparison, the groups treated with the other moisturizing creams all had an increased rate of tumor formation.

Topical applications of the four creams to the UV radiation-pretreated mice for 17 weeks increased the total number of histologically characterized tumors by 69 percent, 85 percent, 24 percent and 58 percent, respectively, compared with the control groups.

Dr. Conney says there appeared to be a difference between the four moisturizers, "but I don't think the data is strong enough to be able to separate them out" or determine the contributions of individual compounds to the tumor-promoting effect of the various moisturizers.