The value of sunscreens is taking some heat from scientists.
An epidemiologist said her own study and a review of other research showed no convincing evidence that using sunscreens keeps people from getting deadly melanoma skin cancer. But that belief is widely held, and other specialists at a science conference cautioned against going into the sunshine without using the lotions.Sunscreens prevent sunburns. Since there is evidence that frequent burns, especially at an early age, trigger melanoma, many experts assume that using sunscreens should help ward off the cancer that strikes about 42,000 Americans a year, killing 7,300.
However, melanoma cases have risen dramatically over the last 25 years even though sunscreen use is more common.
"It's not safe to rely on sunscreen," said Dr. Marianne Berwick, an epidemiologist at Memorial Sloan-Kettering Cancer Center in New York City.
Ten studies have looked at the question, she said at the American Association for the Advancement of Science meeting. Three of them, including her own, found no link between sunscreens and melanoma risk. Two suggested that sunscreens seem to prevent melanoma.
The five others found that melanoma risk actually increased among sunscreen users - probably because people who use them most are already at highest risk because of light complexions.
Several dermatologists strongly disagreed with Berwick's report.
"People should not stop using sunscreen because of this study," said Dr. Michael Thun, director of analytic epidemiology at the American Cancer Society. "The important message is that using sunscreen is only one of several measures to reduce one's risk of skin cancer."
Until there is clear proof that sunscreens are ineffective, "it would be irresponsible to discontinue all recommendations about using sunscreens," said Dr. Darrell Rigel of New York University.
Melanoma may take 20 years or more to develop after excessive sun exposure. Some doctors argue that it is simply too soon to prove that sunscreens are helping, since No. 15 and stronger sunscreens have only been in wide use since the mid-1980s.