Bottle labeled retinol
Credit: Rita Maas

Also known as: Retinoic acid, retinyl palmitate.

Good for: Normal skin, oily skin.

What it treats: Sun damage, acne, aging.

How it works: Retinol, the mild, over-the-counter form of retinoids (which are found in Retin-A and Renova), has been proven to stimulate the production of collagen and the formation of elastic tissue fiber. Over time this reduces wrinkles and prevents new ones. Since retinol can be irritating, avoid it if you have sensitive skin, rosacea, or eczema.

RS picks: Philosophy Help Me, $45, Estée Lauder Diminish Anti-Wrinkle Retinol Treatment; unfortunately, this item is no longer available.