Fulfilling the ancient dream of preserving youthful skin, scientists reported yesterday that a relatively cheap drug used to treat acne can reverse wrinkles and the other signs of aging caused by the sun..

In the [John J. Voorhees] study, 30 patients ranging in age from 35 to 70 rubbed Retin-A on one forearm daily and a cream containing no medication on the other. Half the subjects also tested the drug on their faces. None of them knew which cream contained the drug.

The outer layer of the skin, called the epidermis, becomes thinner as it ages or is damaged by the sun. That causes fine wrinkles just below the surface where blood vessels supplying the skin have been reduced in number over time.