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Alpha-hydroxy is a chemical compound derived from fruit and milk sugars. Alpha-hydroxy acids (AHAs) are use in topical skin care products to exfoliate, or slough away, dead skin cells and promote collagen growth. They can be useful in promoting smoother, even-toned skin and may reduce the appearance of wrinkles and fine lines in some individuals.

AHAs are available in a number of different synthetic and natural formulations. Lactic AHA is derived from milk products, while glycolic AHA is derived from sugarcane. Other AHA compounds include citric acid (from fruit) and malic acid (from apples).

General use

AHAs work by removing dead cells at the surface of the skin. In higher concentrations, it promotes collagen production, which may reduce the appearance of fine lines and wrinkles in the skin. The acids penetrate deep into the skin, where they actually begin to damage skin cells. This skin damage triggers the production of collagen, a fibrous protein and a building block of tissue and skin, as the body attempts to repair the cell damage.

Cosmetic, over-the-counter preparations of alpha-hydroxy must contain less than 10% of the compound according to U.S. Food and Drug Administration (FDA) regulations. This is a high enough concentration to promote exfoliation, but not potent enough to generate collagen production. The concentration of AHA required to produce this effect is only available with a prescription from a dermatologist or licensed healthcare professional, or through professionally administered treatments from a licensed cosmetologist.

Guidelines recommended by the trade regulatory association Cosmetic Ingredient Review have been adapted by the U.S. FDA for consumer AHA products. The Cosmetic Ingredient Review is a self-regulating agency established by the Cosmetic, Toiletry, and Fragrance Association to set safety standards for ingredients used by the cosmetic industry. Trained cosmetologists are permitted to use AHA concentrations as high as 30%, provided these products have a pH level of 3.0 or higher. Health-care professionals such as dermatologists typically use concentrations as high as 5070%.


AHA preparations are available in over the counter and prescription gel, lotion, toner, and cream formulations. An over-the-counter formula that contains between 58% AHA may be more effective. Because FDA regulates these products as cosmetics and not drugs, the manufacturer is not required to list the strength of AHA on the package labeling. However, product ingredients must be listed sequentially in the order of highest concentration, so products which list AHA compounds second or third are usually more beneficial than those who list them in the middle to end of the ingredient list.

The pH level of an AHA product is also important to the product's effectiveness. A higher pH level means the product is less acidic and gentler on the skin, however, a higher pH can also lessen the overall potency of the product. The Cosmetic Ingredient Review guidelines for AHA products specify that consumer AHA products must have a pH of 3.5 or more.

Depending on their skin type, certain individuals may find some carrier formulas (i.e., cream, gel, lotion, toner) more effective than others. Those with dry skin may find moisturizing AHA creams and lotions more effective, while individuals with oily skin may prefer a less oily toner or gel.

Individuals who are prescribed AHA formulations by a healthcare professional should follow their doctor's directions for use of the product.


Buy only those AHA products that conform to the Cosmetic Ingredient Review and FDA recommended guidelines of 10% or less AHA with a 3.5 or higher pH level.

Over-the-counter AHA preparations (those with less than 10% AHA) are designated as cosmetics, rather than drugs, by the U.S. FDA, and therefore do not have to undergo the rigorous testing, review, and approval process required of medical products. In addition, labeling for cosmetics does not require a listing of the concentration of ingredients, although some manufacturers provide this information on their labeling voluntarily. Individuals should try to purchase AHA products that provide detailed ingredient and concentration information to ensure they are purchasing true AHA ingredients in a therapeutic concentration. In addition, if an individual experiences a reaction to an AHA product, they can use detailed labeling to decide if a lower concentration of the product is available and may be right for them.

Individuals who are considering using AHA products for the first time, or who are switching the type of AHA product they use, should perform a skin patch test to check for skin sensitivity to the substance. A small, dime sized drop of the AHA product should be applied to a small patch of skin inside the elbow or wrist. The skin patch should be monitored for 24 hours to ensure no excessive redness, swelling, blistering, or rash occurs. If a reaction does occur, the test can be repeated with an AHA product with a lower alpha-hydroxy acid concentration. Individuals who experience a severe reaction to a skin patch test of AHA are advised not to use the product. A dermatologist or other healthcare professional may be able to recommend a suitable alternative.

AHA products may increase sun sensitivity. Individuals using AHA products should use a high SPF (at least 15 SPF) sunscreen over the AHA formula to protect against burning. Sunscreen should be applied no less than 15 minutes after the AHA formula is applied to prevent neutralizing the acids. Shading the face with a wide-brimmed hat may also be useful. Results of a 1999 FDA study on the use of AHA and UV damage showed that, while AHA decreases the time required for skin to begin to burn, discontinuing use of the AHA product returned skin to normal within a week.

Exfoliative products should be used with care, as over-exfoliation can cause damage to the skin. AHA products should not be combined with other exfoliative products such as facial scrubs, buff pads, or loofahs. In addition, individuals should only use one AHA product at a time.

Higher concentration prescription AHA products have a great likelihood of producing side effects, so individuals taking them should contact their healthcare provider immediately if they experience burning, redness, or any other reaction to the product.

Individuals who experience adverse reactions to AHA treatments should report them to both the manufacturer of the product and to the FDA's Office of Cosmetics and Colors. A patient's dermatologist or health-care provider can also make this report anonymously for the patient. Although these products do not require FDA approval for market release, FDA is responsible for monitoring their safety and can initiate a product recall or removal for a specific brand or formulation if enough adverse effects occur to make these steps necessary.

AHA chemical peels and other high concentration AHA treatments should only be administered by a licensed cosmetologist, licensed dermatologist, or other qualified healthcare professional.

Side effects

Possible side effects of AHA products include:

  • Increased sun sensitivity. Individuals who use AHA are often more sensitive to UV rays.
  • Excessive redness and burning. In high concentrations and/or with individuals with sensitive skin, AHA can cause redness, burning, and even blistering.
  • Swelling. AHA products can cause swelling of the skin and/or eyes.
  • Contact dermatitis . AHA can cause an allergic skin reaction characterized by rash and itching in some individuals.
  • Skin discoloration. Some cases of AHA-related skin discoloration have been reported.

The FDA has sponsored a joint study with the National Toxicology Program to further assess the long-term consequences of AHA product use. Results of the study were not yet available as of July 2000.


There are no known interactions between alpha-hydroxy acid products and other medications and substances when administered in recommended strengths. However, because over-the-counter AHA products are considered cosmetics and not pharmaceuticals, existing research on possible interactions is minimal.

Alpha-hydroxy products may enhance the effects of other products or medications with similar therapeutic properties.



Callan, Annette, ed. All About Skin Care. Oxford, UK: Oxford University Press, 2000.


Kurtzweil, Paula. "Alpha Hydroxy Acids." FDA Consumer. 32, No. 2 (March/April 1998): 30-6.


Cosmetic Ingredient Review. 1101 17th St. N.W. Suite 310, Washington D.C. 20036-4702. (202) 331-0651.

U.S. Food and Drug Administration. Office of Consumer Affairs. FDA (HFE-88), 5600 Fishers Lane, Rockville, MD 20857. (301) 827-5006. To report adverse effects of a cosmetic product, call: (800) 270-8869.

Paula Ford-Martin