According to the research published in theJournal of Investigative Dermatology, mice treated with a batch of common moisturising creams develop more tumours when exposed to UV-rays than those not treated with the creams.

Allan Conney and colleagues used hairless mice that they exposed to UV radiation to mimic exposure to the sun and then, after stopping UV treatment, they applied 5 days a week for 17 weeks 100 mg of four different brands of moisturizers to the animals: Dermabase by Paddock Laboratories, Dermovan by Healthpoint, Eucerin Original Moisturizing Cream by Beiersdorf, and Vanicream by Pharmaceutical Specialties. Mice treated with each of the four brands had an increased rate of tumour formation and tumours of bigger size than UV-treated mice that were not moisturized.

However, significant differences were noted between the moisturizers. Tumour rates increased 95% with Dermovan and only 24% with Eucerin, leading scientists to think that certain ingredients might enhance tumorigenesis in the skin. A new moisturizer prepared without the suspected ingredients (sodium lauryl sulfate and mineral oil) did not show the same tumorigenic effect of increasing the rate of skin cancer in the UV-exposed mice.

Though the research may initially appear alarming, the authors indicate that the significance of these findings has not been established in humans and that further research is required to determine this. Indeed, mouse skin is quite different from human skin and the mice selected for the study were highly susceptible to develop skin tumours. However, the authors believe the research could help to explain the incidence of some types of skin cancer in patients.

In a statement commenting the study and available on its website, German cosmetics maker Beiersdorf said that its Eucerin cream has been on the market for more than 100 years, being used both by individuals with normal skin and those with diseased skin under the care of physicians “without any incidents of this nature ever reported”. The company considers ”the results of this study to be clinically not relevant”.

Several scientists also criticized the study, reported Beiersdorf. For instance, Professor Albert Kligman and Professor Lorraine Kligman from the Department of Dermatology of University of Pennsylvania in Philadelphia said that the authors of the research “have misinterpreted the results [we] published. They incorrectly state that mineral oil increased the percentage of tumours. In fact, we found that petrolatum inhibited carcinogenesis while mineral oil had no preventive effect. It did not enhance carcinogenesis as compared to controls.” The two scientists also added that “hairless mice have a very thin, poorly developed horny layer barrier compared to humans. This predisposes them to tumorigenesis. The result of mouse studies may not have much relevance for man”.

The study protocol was also criticized as mice were preirradiated before applying the moisturizers. Results might have found different if the moisturizers were applied before or concomitantly with the irradiation.