Retinoids — refers to a family of ingredients derived from vitamin A, including retinol, retinyl esters, and retinyl palmitate. Retinoids play an important role in repairing damaged and photodamaged skin. Retinoid treatment can result in the regeneration of the dermal collagen tissue by inhibiting excessive formation of the collagenase enzyme responsible for the breakdown of dermal collagen and by also promoting collagen synthesis. The ability of retinoids to increase collagen types I and II makes them helpful in the prevention of bruising, tearing, and ulceration in mature skin. Retinol has become the preferred retinoid for cosmetic use.