Many of today's over-the-counter (OTC) skin creams and lotions promise to do more than moisturize the skin. They also claim to reduce wrinkles and prevent or reverse damage caused by aging and sun exposure.

Do they work? Some research suggests that wrinkle creams contain ingredients that may improve wrinkles. But many of these ingredients haven't been subjected to intensive research that proves this benefit.

Here are some of the most common types of ingredients found in OTC wrinkle creams, organized by known effectiveness.

Vitamin A (retinol)
Retinol is a vitamin A derivative and is the first antioxidant to be widely used in OTC wrinkle creams. Antioxidants are substances that neutralize free radicals — unstable oxygen molecules that break down skin cells and cause wrinkles. Retinol is less potent than the vitamin A derivative tretinoin, the only prescription topical treatment approved by the Food and Drug Administration for treating wrinkles. Both retinol and tretinoin can cause redness and irritation, but retinol's side effects are usually milder.

• Claim. Works deep below the skin's surface to smooth wrinkles.
• Brand examples. RoC Retinol Actif Pur Anti-Wrinkle Treatment, L'Oreal Dermo-Expertise Line Eraser Pure Retinol Night Treatment.
• The facts. Retinol concentration varies from product to product, and the FDA warns that some OTC preparations may contain almost no retinol. Avoid Vitamin A derivatives if you're pregnant or may become pregnant because they increase the risk of birth defects.

Hydroxy acids
Alpha hydroxy acids, beta hydroxy acids and poly hydroxy acids are all synthetic versions of acids derived from sugar-containing fruits. These acids are exfoliants, substances that remove the upper layer of old, dead skin and stimulate the growth of smooth, evenly pigmented new skin.

• Claim. Improve the look of deeper lines and wrinkles while increasing skin hydration.
• Brand examples. Kiss My Face Peaches & Creme Moisturizer with 8% Alpha Hydroxy Acids, M.D. Forte Facial Cream III with Glycolic Acid.
• The facts. Hydroxy acids stimulate production of collagen, a protein that thickens skin and prevents water loss. Use of these acids may lead to modest improvements in fine lines and wrinkles. Side effects may include burning, itching, pain and possible scarring. Since hydroxy acids increase your susceptibility to sun damage, apply sun protection during use and for at least one week afterward.

Alpha-lipoic acid ( ALA)
Alpha-lipoic acid is an antioxidant that penetrates skin cell membranes, where it neutralizes free radicals and increases the effectiveness of other antioxidants such as vitamins C and E. It may also work as a superficial chemical peel to exfoliate dead skin and reduce the appearance of wrinkles.

• Claim. Diminishes fine lines, wrinkles, brown spots and other skin irregularities. Produces firm, toned skin and a smoother complexion.
• Brand examples. Derma e Alpha Lipoderm Alpha Lipoic/Green Tea Advanced Repair Complex, Zia Natural Skincare Ultimate Oil-Free Moisture.
• The facts. Alpha-lipoic acid appears to reduce fine wrinkles and brown spots. Because side effects include inflammation, however, it's possible that inflammation is responsible for this effect. Larger studies are needed.

Coenzyme Q-10
Coenzyme Q-10 is a nutrient that helps regulate energy production in cells.

• Claim. Improves the skin's ability to fight wrinkles.
• Brand examples. Avalon Organic Botanicals CoQ10 Wrinkle Defense Creme, Nivea Visage Q10 Plus Wrinkle Control Night Creme.
• The facts. Two human (clinical) trials show significant reduction in fine wrinkles around the eyes with no side effects. Other studies show that application before sun exposure protects against sun damage. More research is needed to examine the long-term effects.

Copper peptides
Copper is a trace element found in every cell. In topical products, it's combined with small protein fragments called peptides. Copper peptides enhance wound healing. They also stimulate production of collagen and may enhance the action of antioxidants.

• Claim. Improve the skin's elasticity and hydration to reduce the appearance of fine lines and wrinkles.
• Brand examples. Neutrogena Visibly Firm Night Cream with Active Copper Formula, Neova Night Therapy with Copper Peptide Repair Complex.
• The facts. Some small studies show that copper peptides may modestly improve fine wrinkling, age spots and sun damage with no side effects. More research is needed, however.

Growth factors
Growth factors are naturally occurring hormones found in plants and animals. They act as chemical messengers between cells. Kinetin, a plant growth factor, is the one most often used in cosmetics.

• Claim. Reduce the appearance of fine wrinkles and uneven skin tone.
• Brand examples. Almay Kinetin Skincare, Kinerase Cream.
• The facts. Kinetin may improve wrinkles and uneven pigmentation with minimal irritation. It's unclear how it works, but it may help reduce wrinkles by helping skin retain moisture and by stimulating the production of collagen. It also may be a potent antioxidant. Large-scale studies are needed to determine its long-term safety and effectiveness.

Soy isoflavones
Protein extracts of soybean and soymilk contain several different estrogen-like substances called isoflavones. Because they may mimic the effects of estrogen, they're sometimes called phytoestrogens. Phytoestrogens may produce wrinkle-reducing effects on skin that are similar to those resulting from hormone therapy.

• Claim. Reduce fine lines and wrinkles.
• Brand examples. Aveeno Positively Radiant Anti-Wrinkle Cream, Archipelago Botanicals Milk Soy Cream.
• The facts. Animal studies show that soy isoflavones protect skin against sun damage and may increase production of hyaluronic acid, a substance that thickens skin and reduces wrinkles by binding to water molecules in skin. A small clinical study of soy isoflavones shows that they may lighten age spots. Although oral soy isoflavones may increase the risk of some cancers, it's unknown if topical products do the same. Researchers believe that soy isoflavones may help reduce wrinkles, but caution that more human research is needed to determine their safety and effectiveness.

Tea extracts
Green, black and oolong tea contain compounds with antioxidant and anti-inflammatory properties. Green tea extracts are the ones most commonly found in wrinkle creams.

• Claim. Repair sun damage, leaving skin toned and refined.
• Brand examples. Derma e Retinol and Green Tea Advanced Renewal Creme, Sudden Change Eye Gel with Green Tea.
• The facts. Animal studies of topical tea extracts show that they protect against skin cancer and prevent sun damage. Human studies of topical green tea extracts also show that they protect against sun damage with no side effects. But it's not clear if extracts in creams and lotions degrade over time. Although preliminary research shows that tea extracts may reduce wrinkles, larger human studies are needed to confirm the effectiveness.

Vitamin C
Vitamin C is an antioxidant nutrient that helps recycle vitamin E. It also promotes collagen formation.

• Claim. Repairs and protects skin by stimulating cell renewal and increasing healthy circulation.
• Brand examples. Avalon Active Organics Vitamin C Moisture Plus Lotion with SPF 15, ShiKai Dermaceutical Formulation Nighttime Renewal Cream with Bio-Active Vitamin C.
• The facts. Topical vitamin C may reduce wrinkles, thicken skin and protect against sun damage. It's difficult to manufacture and degrades rapidly, however, so it must be stored in airtight, light-resistant containers. Many of the first vitamin C products couldn't penetrate the skin deeply enough to be effective, but newer products may be more absorbent. Side effects may include stinging and irritation. Larger studies are needed to prove whether topical vitamin C can reduce wrinkles.

Vitamin E
Vitamin E, an antioxidant nutrient, is the major antioxidant found in human skin. Declining levels in skin are associated with wrinkles.

• Claim. Neutralizes free radicals for a soft, smooth, radiant complexion.
• Brand examples. Nutra-E Pure Vitamin E Skin Cream, Olay Moisture-Rich Cream Cleanser with Olay Moisture and Vitamin E.
• The facts. Animal studies show that topical vitamin E may reduce wrinkling. One of the few human studies shows a slight reduction in wrinkling, skin roughness, length of facial lines and wrinkle depth. Side effects may include swollen, reddened and itchy skin (contact dermatitis). Tocopherols and tocopherol acetate are the most common forms of vitamin E found in cosmetics, but they may be poorly absorbed by skin. More research is needed to determine if vitamin E reduces wrinkles effectively by itself or in combination with other antioxidants.

Collagen
Collagen is a large, fibrous protein that keeps your skin supple and elastic. Collagen diminishes with age, contributing to wrinkling and sagging.

• Claim. Firms the skin while minimizing the appearance of fine lines.
• Brand examples. St. Ives Collagen Elastin Essential Moisturizer, University Medical Face Lift Collagen 5 Cell Regeneration Cream.
• The facts. Many skin creams contain collagen, which supposedly nourishes the skin and reverses the signs of aging. But collagen isn't absorbed through the skin and doesn't increase the body's production of collagen. Applying a collagen cream may give the sensation of firmness, but it's probably due to skin hydration that could be achieved by using any moisturizer.

The FDA considers these creams and lotions to be cosmetics, which are defined as having no medical value. So the FDA regulates them more lightly than it does drugs, which are defined as "products that cure, treat, mitigate or prevent disease, or that affect the structure or function of the human body."

The FDA steps in, however, when advertisements portray cosmetics as drugs. In 2004, for example, the FDA ordered a manufacturer to stop advertising its wrinkle cream as "proven to reduce deep wrinkles up to 70 percent."

The FDA also intervenes when cosmetics contain ingredients that may pose a potential health hazard to consumers. For example, in 2002, the FDA ordered manufacturers of products containing alpha hydroxy acids to include a warning label stating that the acids may increase the risk of sunburn.

Because the FDA doesn't regulate cosmetic products for effectiveness, there's no guarantee that any OTC product will reduce your wrinkles or even contain any of its advertised ingredients.

If you shop for such products in a department store or pharmacy or on the Internet, you'll find hundreds of different brands containing a confusing array of ingredients. You may be tempted to experiment with different brands until you find one that works. But this approach may be expensive. It also may cause skin irritation and deprive you of the benefits of an effective skin-care regimen.

Different skin creams and lotions may be more effective on dry, oily or sensitive skin. A dermatologist can help you take the guesswork out of selecting a wrinkle cream or lotion by assessing your skin type, evaluating your skin's condition, and determining if you're allergic to certain ingredients.

If you're looking for a face-lift in a bottle, you probably won't find it in an anti-aging skin cream. Still, the use of such products may result in slight to modest improvements in wrinkles. Combining the right product with a proven medical or surgical treatment for wrinkles may be the most effective way of achieving a younger-looking face.