We all have heard about them but do we know what they are and what they do for our skin? It turns out that a-hydroxy acids (AHAs) are important components of optimal skin care and their benefits have been studied and documented for some time now. These distinctive molecules provide us with plethora of opportunities for individualizing skin treatments to fit our unique needs. They can be used as a monotherapy or be a part of a comprehensive skin care management. This article will review the current understanding of AHAs, their biology as well as their benefits and risks when used in cosmetic and medical applications.
WHAT IS AN ALPHA HYDROXY ACID?
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. Further discussion in this article will focus on the properties and benefits of glycolic acid (GA).
ALPHA HYDROXY ACID AT DIFFERENT CONCENTRATIONS
In low concentrations, 5 – 10% as is found in many over the counter products (e.g. Reversa ® product line), 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, photodamage, wrinkling as well as melasma. Care needs to be taken to avoid irritation as this may result in worsening of melasma or other pagmentary problems. Newer formulations (e.g. ReversaŽ product line) 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). Also you can read about “before and after aging lips” here
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 photodamage (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 hyperpigmentation, persistent redness, scaring as well as flare up of facial herpes infections (“cold sores”).
Alpha hydroxy acids, and glycolic acid in particular, are an important part of skin care. When used appropriately, they have been shown to correct mottled dyspigmentation, melasma and fine wrinkles. They seen to affect skin cells deeper than their proposed penetration into the skin suggesting that their benefits are more than those just related to skin exfoliation. As such, AHAs deserve our attention and key place in the overall skin care management.