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α-hydroxy acids, or alpha hydroxy acids (AHAs), are a class of chemical compounds that consist of a carboxylic acid substituted with a hydroxy group on the adjacent carbon. They may be either naturally occurring or synthetic. AHAs are well-known for their use in the cosmetics industrycitation needed. They are often found in products claiming to reduce wrinkles or the signs of aging, and improve the overall look and feel of the skincitation needed. They are also used as chemical peels available in a dermatologist's office, beauty and health spas and home kits, which usually contain a lower concentrationspecify. Their effectiveness is documented.
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Application
Alpha hydroxy acids is a group of compounds derived from food products including glycolic (from sugar cane,) lactic (from sour milk,) malic (from apples,) citric (from fruits) and tartaric acid (from grape wine.) For any topical compound, including AHA, it must penetrate into the skin where it can act on living cells. Small molecular size is one characteristic that is important in determining compound's ability to penetrate the top layer of the skin. In that respect, glycolic acid (the smallest AHA) is a clear winner and accounts for the popularity of this product in both cosmetic as well as medical preparations.
Alpha Hydroxy Acid At Different Concentrations
In low concentrations, 5 - 10% as is found in many over the counter products, GA reduces cell adhesion in the top layer of the skin. This action promotes exfoliation of the outermost layer of the skin accounting for smother texture following regular use of topical GA. This relatively low concentration of GA lends itself to daily use as a monotherapy or a part of a broader skin care management for such conditions as acne, photo-damage, wrinkling as well as melasma. Care needs to be taken to avoid irritation as this may result in worsening of melasma or other pigmentary problems. Newer formulations combine GA with an amino acid such as arginine and form a time-release system that reduces the risk of irritation without affecting GA efficacy. The use of an anti-irritant like allantoin is also helpful. Because of its safety, GA at the concentrations below 10% can be used daily by most people except those with very sensitive skin.
In higher concentrations, between 10 and 50%, its benefits are more pronounced but are limited to temporary skin smoothing without much long lasting results. This is still a useful concentration to use as it can prepare the skin for more efficacious GA concentrations (50 - 70%) as well as prime the skin for deeper chemical peels such as TCA peel (trichloroacetic acid).
At higher concentrations, 50 - 70% applied for 3 to 8 minutes under the supervision of a physician, GA promotes slitting between the cells and can be used to treat acne or photo-damage (such as mottled dyspigmentation, melasma or fine wrinkles). The benefits from such short contact application (chemical peels) depend on the pH of the solution (the more acidic the product [lower pH,] the more pronounced the results,) the concentration of GA (higher concentrations produce more vigorous response,) the length of application and prior skin conditioning such as prior use of topical vitamin A products. Although single application of 50 - 70% GA will produce beneficial results, multiple treatments every 2 to 4 weeks are required for optimal results. It is important to understand that GA peels are chemical peels with similar risks and side effects as other peels. Some of the side effects of AHAs chemical peeling can include hyper-pigmentation, persistent redness, scaring as well as flare up of facial herpes infections ("cold sores").
Safety
AHAs are generally safe when used on the skin as a cosmetic agent using the recommended dosage. The most common side-effects are mild skin irritations, redness and flaking. The severity usually depends on the pH and the concentration of the acid used. Chemical peels tend to have more severe side-effects including blistering, burning and skin discoloration, although they are usually mild and go away a day or two after treatment.
The FDA has also warned consumers that care should be taken when using AHAs after an industry-sponsored study found that they can increase photosensitivity to the sun.
See also
- Beta hydroxy acid
- Salicylic acid, a β-hydroxy acid
References
- ^ An evaluation of the effect of an alpha hydroxy acid-blend skin cream in the cosmetic improvement of symptoms of moderate to severe xerosis, epidermolytic hyperkeratosis, and ichthyosis. Cutis. 1998 Jun;61(6):347-50.
- ^ Alpha Hydroxy Acids for Skin Care by Paula Kurtzweil, FDA Consumer, March-April 1998, Revised May 1999.
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- This page was last modified on 7 December 2008, at 00:21.
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