"Sunscreens are difficult to use properly," says Daniel Yarosh, president of AGI Dermatics, a Freeport, N.Y., biotech company that is developing a lotion to help the skin mend itself. "Science is trying to find something better."

The beyond-sunscreens research falls into two categories. One approach helps repair cellular skin damage after too much sun exposure. The other approach makes the skin less sensitive to the sun.

"The research in this field is still relatively early," says Dr. Henry W. Lim, chairman of the department of dermatology at Henry Ford Hospital in Detroit. "But I think this is something that will continue to develop."

The most rigorously tested damage-control product thus far is called Dimericine, developed by AGI Dermatics.

Currently in stage 3 clinical trials, the product is based on an understanding of how cells try to repair themselves when damaged.

"The idea that people can have a natural repair mechanism is known," Yarosh says.

"What is new is that there are things we can do to optimize it. We're moving into a stage of understanding how the cell responds to damage - what genes get turned on in young skin and what genes get turned on in old skin and how can we make old skin act young.

"That's what makes this so exciting."

Dimericine, he says, contains a customized enzyme that can recognize DNA damage caused by ultraviolet light and speed up repair.

"It's like patching a tire," he says. "You can get rid of the damage, and the DNA goes back to being normal.

"We call it a morning-after lotion. It can be used after sun exposure but before damage has arrived."

A study of 30 people, published in 2001 in the Lancet medical journal, showed the lotion reduced the incidence of precancerous growths, called actinic keratoses, by 68 percent and basal cell carcinoma by 30 percent.

FDA approval, which is unlikely before 2010, would mean that the estimated 58 million Americans with precancerous skin lesions and others at high risk for skin cancer could benefit, Yarosh says.

"If indeed this is shown to be beneficial in otherwise healthy individuals, it would obviously be a very exciting development in this field," says Lim, who is not involved in the product's development.

AGI Dermatics also makes an over-the-counter product that purports to help repair DNA-damaged skin cells. Called Remergent, it uses botanical extracts to help stimulate the normal repair mechanism to prevent wrinkles and other cosmetic effects of sun damage.

Several supplement manufacturers are touting sunburn-prevention pills they say can protect the skin by limiting reaction to the sun. The best known is Heliocare, which contains the antioxidant polypodium leucomotos, an extract from a fern that grows in South and Central America.