The substances collagen and elastin give skin its firmness and elasticity. With age, though, the collagen and elastin content of the skin gradually decreases. As a result, the skin becomes looser, weaker, less elastic, and drier. In addition, the fat pads under the skin begin to disappear. Wrinkles form, and the skin begins to sag.

This gradual loss of structure has several causes: genetic programming (a built-in “clock” that causes aging), cumulative sun damage (photoaging), and direct chemical effects from cigarette smoking and/or abrasive chemicals. Sun damage additionally causes fine wrinkles that disappear when stretching the skin, surface roughness, mottled pigmentation, "liver" spots, and skin cancer.

In people who already have signs of aging skin and wish to reverse it, a number of treatments are available.

The drug tretinoin (retinoic acid, or Retin-A), a substance related to vitamin A, has been shown effective for reversing the fine wrinkles, splotchy pigmentation, and rough skin of sun damage.

The hormone estrogen is thought to help restore normal skin tone in menopausal women, but the evidence for this widely held belief remains weak.

More aggressive treatments for aging skin include injections of botulin toxin, dermabrasion, chemical peels, soft tissue augmentation, laser resurfacing, and GORE-TEX® threads. For detailed information on the relative merits and demerits of these methods, consult a dermatologist or plastic surgeon.

Two classes of natural treatments have shown promise in the treatment of aging skin: alpha-hydroxy acids (AHAs) and antioxidants. However, the evidence that they work remains incomplete, and AHAs can cause significant side effects.

Alpha-hydroxy Acids

Alpha-hydroxy acids, such as glycolic acid and lactic acid, are substances derived from fruit and dairy products. These are milder relatives of the substances used by dermatologists in chemical peels, which are designed to remove damaged layers of the skin. In recent years, cosmetic manufacturers have begun to add AHAs to numerous skin-care products.

Meaningful evidence in support of AHAs comes from one double-blind, placebo-controlledstudy reported in 1996.1 This 22-week study enrolled 74 women with sun-damaged skin. Participants received either 8% glycolic acid, 8% L-lactic acid, or placebo cream, and applied it to the face and forearm. Although participants showed improvements in each of the three groups, superior results were achieved with each of the AHA creams than with the placebo cream.

Another double-blind study compared estrogen cream, glycolic acid cream, and their combination against placebo.26 Both estrogen and glycolic acid improved skin aging.

AHAs are not always harmless. Possible side effects include burning, blistering, severe redness, swelling (especially in the area of the eyes), bleeding, rash, and increased sensitivity to the sun.2 There are also concerns that AHAs may increase risk of skin cancer. For all these reasons, the FDA is currently investigating the use of AHAs in cosmetic products to determine whether they should be reclassified as drugs.

Antioxidants

The ultraviolet light from the sun creates free radicals, naturally occurring substances that can harm many tissues of the body, including the skin. Antioxidants are substances that neutralize free radicals. On this basis, various antioxidants have been investigated for their potential usefulness in treating or preventing photoaging. (Note, however, the surprising results described at the end of this subsection.)

A small, 3-month, double-blind, placebo-controlled study found benefit with a cream containing 5% alpha-lipoic acid.27 Use of this antioxidant substance improved several measures of aging skin as compared to placebo, especially skin roughness. Benefits have also been seen in preliminary studies with a cream containing vitamin C.3,4

In a small double-blind study, use of mixed antioxidants ( lycopene, beta-carotene, vitamin E, andselenium) for 12 weeks improved skin roughness and scaling.36

Oligomeric proanthocyanidin complexes (OPCs) made from grape seed or pine bark are widely marketed for the treatment of aging skin. These substances, closely related to bioflavonoids, have antioxidant properties and might also protect and strengthen collagen and elastin.5-10 These effects provide theoretical reasons to believe that OPCs might be helpful for the treatment of aging skin. However, despite widespread marketing, no properly designed studies have been reported to indicate that OPCs really provide any benefit.

In an 8-week double-blind, placebo-controlled study of 40 women who already had sun-damaged skin, combined use of oral green teaand a topical green tea cream failed to prove more effective than placebo in improving the condition of sun-damaged skin.29 Some possible benefits were seen in microscopic evaluation of skin condition.

Antioxidant substances have also been studied as aids to preventing sun damage.

Studies on laboratory animals found that topical vitamin C and vitamin Ehelped prevent burning on exposure to ultraviolet light.11-14

One small, double-blind study found that 2 g of vitamin C and 1,000 IU of vitamin E taken orally for 8 days resulted in a modest decrease of "sunburn" induced by ultraviolet light.15In addition, a 50-day, placebo-controlled study of 40 people found that higher doses of these vitamins provided a sun protection factor of about 2.16(Compare this to the sun protection factor of 15 or higher in many sunscreens.) It appears that these vitamins must be taken together for best effect; when used alone they do not appear to work.16,17,40

Oral use of beta-carotene, lycopene, and othercarotenoidshas shown preventive effects in some but not all studies.25,30-31Benefits have also been seen with mixtures of various antioxidants taken together (vitamin E, zeoxanthin, lutein, beta-carotene, and others).32-33

Oral vitamin Ahas shown some promise for preventing skin cancer in people at risk for it, but the doses used in studies were quite high, considerably above current recommendations for the maximum safe dose.28 ( Note: Do not use vitamin A along with the drug tretinoin. See Safety Issues.)

Topical vitamin A may be helpful for treatment of aging skin. One double-blind, placebo-controlled study found that a 0.4% vitamin A lotion applied three times a week significantly reduced the number of “fine” wrinkles in seniors.42 Benefits were also seen in terms of some biochemical measures of skin health.

Because these antioxidants work in an entirely different manner from standard sunscreen, it appears reasonable to believe that they might offer a synergistic effect if taken with sunscreen. However, this hypothesis has not been studied.

Other substances with antioxidant actions that have shown some promise for treating or preventing aging skin include cocoa,39Vitis viniferaextract,43milk thistle,21 and zinc.21 However, the supporting evidence that use of these substances (taken either orally or topically) offers any benefit for the skin remains far too preliminary to be relied upon at all.

Note: Any discussion of the potential benefits of antioxidants for preventing cancer must include the startling finding of a large study that tested the effect of mixed antioxidants. This trial, enrolling 7,876 women and 5,141 men, evaluated the potential benefits of a combination of vitamin C, vitamin E, beta-carotene, selenium, and zinc for preventing cancer. According to results published in 2007, no benefits were seen among male participants, but among women, skin cancer rates actually appeared toincrease.44 The cause of these findings remains unclear.