MANILA, Philippines?A study published online this week in the Journal of Investigative Dermatology suggests that some commercially-available moisturizers have carcinogenic effects on the mice used to study how skin cancers form in humans.

There are generally two kinds of skin cancers often caused by ultraviolet radiation from the sun: melanomas marked by pigmented spots that change shape or color; and nonmelanoma cancers typically marked by bumps on areas usually exposed to sunlight such as the face and arms.

Since the World Health Organization estimated that one in three cancers being diagnosed worldwide is a form of skin cancer, such an animal model is useful. But the New Jersey-based researchers also stressed that the hairless mice used as an animal model to study how nonmelanoma skin cancers develop aren?t exactly like humans.

For example, the mice have thinner skins than humans, so they won?t have identical reactions to spending too much time in the sun. In other words, people shouldn?t worry about having to choose between dry skin and possibly getting cancer based on these results.

Unplanned

State University of New Jersey cancer researcher Allan Conney and his colleagues hadn?t even planned on finding such carcinogenic properties in the moisturizing products. They?d been looking at caffeine as a potential ingredient in moisturizers based on studies indicating its potential for reducing skin cancers caused by the sun was reduced.

Using mice predisposed to develop tumors later in life based on prolonged exposure to sunlight early on?a model that mimics how skin cancers can form in humans years after they?ve spent too much time in the sun?the researchers found that the mice treated with small amounts of the moisturizer used for this first test developed more tumors faster than the control mice left untreated.

Intrigued, Conney and his colleagues then conducted a larger experiment involving seven groups of 30 mice each. Five days a week for 17 weeks, each mouse in five of the seven groups had their skin massaged with very tiny amounts of either water or one of four different commercial moisturizers.

The fifth group was treated with a moisturizing cream the researchers had custom-made without any of the ingredients they suspected of being carcinogenic in mice based on studies done by other researchers. One such suspected ingredient present in some of the commercial moisturizers but excluded from the specially prepared formulation was mineral oil. Acting as the controls, the final group was left untreated during the same time period.

More tumors

While the researchers weren?t surprised to find that tumors formed on most of the mice in each group because they?d been predisposed to do so, they did find a difference in the number of tumors and their sizes based on what had been applied to their skin. In general, more tumors developed in the four groups treated with the commercial moisturizers than in the other groups. The tumors were also larger in the mice from the commercially moisturized groups.

However, the group treated with the custom-made moisturizer had tumors of the same number and volume as did the group treated with water. It should be noted though, that this moisturizer was made for research purposes only and is not available on the market.

When applied to these mice then, ?several commercially available moisturizing creams increase the rate of formation and number of tumors when applied topically,? the researchers concluded in their paper. ?Further studies are needed to determine the effects of topical applications of moisturizing creams on sunlight-induced skin cancer in humans.?

E-mail the author at massie@massie.com.