Some sunscreen lotions may not prevent malignant melanoma, the sometimes fatal skin cancer that attacks people who have been over-exposed to sunlight or sunlamps, cancer researchers said Tuesday.
The researchers indicated there also is a chance that sunscreens actually may lead to melanomas by giving sunbathers a false sense of security.
The possibility that sunscreens may be more harmful than helpful was announced by cancer specialists at M.D. Anderson Cancer Center in Houston after tests on mice. The results were published in this month’s Journal of the National Cancer Institute.
“These findings aren’t going to make sunscreen producers happy,” an M.D. Anderson spokesman said.
Led by Drs. Margaret Kripke and Peter Wolf, the researchers tested three popular sunscreens by daubing them on the ears and tails of laboratory mice.
Mice later exposed to ultraviolet light generated by sunlamps developed more melanomas than mice that didn’t get sunlamp treatments, the researchers reported.
Kripke said sunscreens do prevent sunburn but also encourage sunbathers and sunlamp enthusiasts to overexpose themselves to UV light.
Currently, 32,000 Americans annually end up with melanoma moles that spread quickly. Each year, there are 6,800 deaths from melanoma.
Most melanomas occur in middle-aged and elderly whites who have been exposed to a great deal of sunlight for many years. In the U.S., southerners contract three times more melanomas than northerners. Surgery is the only treatment.
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The M.D. Anderson researchers noted health problems that occur in laboratory mice don’t always occur in humans, and their findings should be regarded as a possibility, not a conclusion.
An editorial in the NCI Journal said the study should encourage people to adopt a “safe sun” strategy, that is, to wear a hat and protective clothing, stay in the shade, don’t sunbathe during peak UV hours-10 a.m. to 2 p.m.-and wear sunglasses.
The journal also recommends reducing the amount of sunlamp radiation and avoiding tanning parlors.
Kripke recommended using a sunscreen but not if it encourages its user to remain in the sun for prolonged periods. And he said to be aware that a layer of lotion should be applied every 60 to 90 minutes and immediately after swimming or perspiring heavily.