Photoaging is the effect on the skin of chronic ultraviolet irradiation superimposed on intrinsic aging. Photoaged skin may be wrinkled and have irregular hyperpigmentation or depigmentation, telangiectasias, actinic keratoses or invasive carcinoma. Over-the-counter topical treatments for photoaging have been used by persons interested in improving the appearance of their skin. Some of these agents have been compounded into cosmetics. Consultants from The Medical Letter on Drugs and Therapeutics reviewed the data on topical tretinoin and alpha-hydroxy acids to determine their effectiveness in improving the appearance of aging skin.

Topical tretinoin, initially approved by the U.S. Food and Drug Administration solely for the treatment of acne, has been used for years to treat photoaging of the skin. It is now approved by the FDA in a 0.05 percent formulation in an emollient cream for the treatment of photoaged skin. Tretinoin is a metabolite of vitamin A, which is known to increase formation of collagen in the dermis. Side effects, which increase at higher concentrations, include erythema, burning, itching and peeling. Tolerance often develops with continued use. Oral tretinoin is a known teratogen; consequently, topical therapy is not advised during pregnancy.

Several three- to six-month double-blind trials have shown that use of tretinoin cream modestly improves fine wrinkling, surface roughness and pigmentary changes in mildly to moderately affected skin. Compared with the vehicle alone, tretinoin cream has also been shown to lighten the appearance of prominent hyperpigmented macules on the face, arms and hands. The 0.025 percent formulation appeared to be as effective as the 0.1 percent strength and was better tolerated. Some histologic improvements in treated skin have continued to occur, although some skin regressed through four years of treatment.

Alpha-hydroxy acids are widely used in cosmetic products. Only one controlled trial has been conducted to date. In this study, more than 70 percent of patients treated with lactic acid or glycolic acid reported improvement in the appearance of photoaged skin compared with 40 percent of patients who did not use lactic acid or glycolic acid. Low concentrations of alpha-hydroxy acids appear to be less irritating than tretinoin, and no adverse effects have been reported, although no long-term studies have been conducted. High-concentration alpha-hydroxy acid peels have been known to cause post-inflammatory hyperpigmentation and have been associated with eruption of herpes simplex lesions.

Other agents such as oral and topical estrogen or vitamins C and E have been reported to reverse some effects of photoaging; however, controlled trials are lacking.

Consultants from the Medical Letter conclude that the topical application of tretinoin for four to six months can cause modest improvement in photoaged skin and that these improvements may persist, especially with continued use. Data on alpha-hydroxy acids are lacking and, despite widespread use in cosmetic products, their effectiveness in improving photoaged skin has not been established.