Alpha hydroxy acids (AHA) are a staple of numerous skin care product lines. They are occasionally touted as a new treatment, but in fact their cosmetic use has started several decades ago. AHA are a group of structurally related organic acids found in natural sources or synthesized in the laboratory.
Before we go any further, it should be noted that skincare products based on alpha hydroxy acids are often ridiculously overpriced. Alpha hydroxy acids are very simple, inexpensive chemicals. The cost of alpha hydroxy acids contained in a typical jar of alpha hydroxy acids-based cosmetics is a fraction of a dollar. The effectiveness of an alpha hydroxy acids skincare product depends mainly of the concentration of alpha hydroxy acids rather than accompanying inactive ingredients with scientific-sounding names. Provided alpha hydroxy acids concentrations are the same, an affordable department store brand would bring the same skin benefits as its overpriced counterparts.
There are two different ways in which alpha hydroxy acids are commonly used: (1) high strength alpha hydroxy acids are used by dermatologists in chemical peels. Several studies convincingly demonstrated that such peels can reverse some signs of skin aging. In a study at the University of Los Angeles, California, forty five volunteers were treated with 50 percent glycolic acid or vehicle alone. The treatment was applied to one side of the face, forearms and hands for 5 minutes once weekly for 4 weeks. The researchers concluded that "application of 50 percent glycolic acid peels improves mild photo aging [aging due to sun damage] of the skin." Another study conducted at Hahnemann University School of Medicine, Philadelphia, Pennsylvania, tested a lotion containing 25 percent of glycolic, lactic or citric acid against a placebo lotion. The treatment was continued for 6 month. Alpha hydroxy acids treatment lead to a 25 percent increase in skin thickness, improved quality of elastic fibers and increased density of collagen. The researches concluded that alpha hydroxy acids "produced a significant reversal of epidermal and dermal markers of photo aging."
Peels with high strength alpha hydroxy acids (over 15%) should not be done without the supervision of a dermatologist.
These days the most common use of alpha hydroxy acids is in OTC skincare products formulated for regular use. Most such products contain relatively low concentrations of alpha hydroxy acids, usually 5-15 percent. Benefits of these skincare products are less clear. Products with alpha hydroxy acids concentration below 8% appear to be of no benefit. Most studies of 8 - 15% alpha hydroxy acids report very modest improvements in wrinkles and skin smoothness. Concentrations at the high end of this range might be a little more effective but are more likely to cause irritation.