Caught without sunscreen?A new lotion is in the works that promises to help reverse skin damage caused by the sun. The "morning after" cream, called Dimericine, contains an enzyme that repairs the DNA damage inflicted by the sun's ultraviolet rays. Though not yet approved by the Food & Drug Administration, the cream has been shown to reduce the occurrence of pre-cancerous lesions and skin cancers in patients with xeroderma pigmentosum (XP), a rare condition that causes the skin to burn very easily, making them more susceptible to skin cancers. The National Cancer Institute calls Dimericine "intriguing" and is sponsoring a clinical trial. "Sun damage accumulates in your skin," says Jon Klein, vice president of Applied Genetics Dermatics, which developed Dimericine. "If you don't repair the damage, those cells can mutate and cause skin cancer." Dr. Mark Lebwohl, chairman of the department of dermatology at Mount Sinai School of Medicine, is encouraged by the data. "Dimericine may be very useful for people with a predisposition to skin cancer," he says. It does not, however, stop the painful effects of sunburn. Though the FDA won't release an approval date, some say Dimericine could be available to XP patients as soon as next year.