AHAs, also called alpha hydroxy acids, have five major types: glycolic, lactic, malic, citric and tartaric acid. The most commonly used AHAs are glycolic (from sugar cane) and lactic acids (from milk) because of their special ability to penetrate the skin and the most accumulated research on their functionality for skin.
AHAs “unglue” the outer layer of dead skin cells. This helps increase cell turnover by removing the built-up top layers of skin and so allowing healthier cells to come to the surface. Removing this dead layer can improve skin texture and color, unclog pores, and allow moisturizers to be better absorbed by the skin. AHAs help to improve the appearance of sun-damaged skin, dry skin and thickened skin caused by a variety of factors, including abnormal cell growth, smoking and heavy moisturizers.
In addition to exfoliating the skin, AHAs also have water-binding properties. They can provide an added benefit by helping to keep water in the skin while at the same time exfoliating it.
AHAs peels are most effective when done regularly. Four to six treatments, once a week, are generally recommended for optimal results.