"I'm advising my patients not to use it," said Dr. John Romano, a dermatologist at the New York Hospital of Cornell Medical Center, referring to Coppertone Natural Tan Accelerator. "I say don't use it until there's more information on how it works."

The Coppertone product, made by Schering-Plough Consumer Operations Division, has been on the market for a year. It is one of several similar products developed in the wake of Estee Lauder's fast-selling "Golden Sun Pre-Tan Accelerator," which has been on the market for two years.

But some specialists say that claims made in ads for the products imply that they work like a drug by speeding up cellular production of pigments: "Not a dye or a bronzer, it actually stimulates your body's own natural tanning process," says a Coppertone ad.