THE beauty aisles of a typical drugstore are a veritable fortress stacked with lotions and potions that promise to turn back the clock, rejuvenate the skin and restore a youthful glow. Their labels list an arsenal of ingredients —alpha hydroxy acids, antioxidant vitamins, green tea, copper, caffeine, soy, peptides, among many others.

Yet within the walls of products and tiers of claims, one ingredient still stands out: Retin-A. It is available in prescription-strength products, including generic formulations, and under brand names like Retin-A Micro, Renova, Avage and Tazorac. Its less potent over-the-counter cousin, retinol, is found in products on department and drugstore shelves.

According to the Mintel Global New Products Database, nearly 300 retinol-containing cosmetics have hit the market since 2003. The latest crop includes Neutrogena Healthy Skin Anti-Wrinkle Intensive Eye Cream, RoC Retinol Correxion Deep Wrinkle Daily Moisturizer with SPF 15, Avon Anew Line Eliminator Neo-Retinol Line Plumper SPF 15, MD Skincare Alpha Beta Daily Face Peel and overnight creams like SkinCeuticals retinol 0.5 and 1.0 formulas.

With so many doctors and beauty companies on a hunt for the next big anti-aging product, why do Retin-A and retinol still have so much appeal? The answer, many dermatologists say, is simple: They work.