As more studies say that the incidence of the most lethal form of skin cancer, melanoma, has increased by 50% in the past years, new findings suggest that common moisturizing creams help skin cancers spread because they have tumorigenic (tumor-causing capability) activities.

Researchers from the Rutgers University’s Susan Lehman Cullman Laboratory for Cancer Research studied the effects of four common brands of skin moisturizers on the skin of hairless mice exposed to UV radiation, which induced forms of non-melanoma skin cancer. 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.

They found that the mice treated with moisturizers after the exposure to UV radiation showed an increased risk of tumor formation. These tumors were larger than those on untreated mice.

Lead investigator Allan Conney said the findings raise a “red flag indicating that there’s a need to determine whether or not these products could cause this problem in people.” “And we really don’t know that from this study, which looked only at mice. ... People aren’t mice,” he added.

At the end of the study, researchers found that Dermabase increased the total number of tumors in mice treated with moisturizer after the exposure to UV radiation by 69%, Dermovan increased the number of tumors by 95%, Eucerin increased the total number of tumors by 24%, Vanicream increased the total number of tumors by 58%.

Researchers concluded that companies that make moisturizers should test their products. They said they didn’t know what ingredients in these moisturizers are responsible for the tumorigenic activity.

The incidence of melanoma in young women rose to 13.9 per 100,000 in 2004 from 9.4 per 100,000 in 1980. In young women the melanoma rate went from 5.5 cases per 100,000 per year in 1973 to 9.4 in 1980, and it kept rising to 13.9 in 2004, according to a report published in the Journal of Investigative Dermatology that analyzed cancer statistics for men and women ages 15 to 39 collected through the NCI’s Surveillance, Epidemiology and End Results (SEER) Program. Skin cancers account for more than half of all cancers combined.

Risk factors for nonmelanoma and melanoma skin cancers include: unprotected and/or excessive exposure to ultraviolet (UV) radiation, family history, multiple or atypical moles, severe sunburns as a child. Researchers blame the increased trend of skin cancers on the overuse of tanning, saying excessive UV radiation exposure lead to a greater extent of women developing skin cancer including the deadliest form, melanoma.

The American Cancer Society estimates that 59,940 new cases and 8,420 deaths will occur from melanoma this year. The good thing is that overall deaths from melanoma in young adults decreased. Most non-melanoma skin cancers develop on sun-exposed areas of the body, like the face, ear, neck, lips, and the backs of the hands. Most of the more than 1 million cases of non-melanoma skin cancer diagnosed yearly in the United States are considered to be sun-related, according to the American Cancer Society.