and are known as hydroxy acids.
Alpha hydroxy acids have been an ongoing craze of skincare industry for several years, although their cosmetic use has started several decades ago. They are a group of structurally related organic acids found in natural sources or synthesized in the laboratory. With increasing research into what causes wrinkles and the effects of photoaging, alpha hydroxy acids have increased greatly in popularity. Alpha hydroxy acids have been used for thousands of years as a skin rejuvenating product. Cleopatra is reported to have bathed in sour mild (lactic acid) to improve her complexion. Now hydroxy acids are a common additive to numerous skin care products including moisturizers, cleanser, toners, and masks.
AHA cosmetics are believed to have derived from the "chemical peels" that dermatologists and plastic surgeons have used for years. The peels, typically trichloroacetic acid, phenol, resorcinol, and salicylic acid, help remove undesirable signs of skin aging, such as discoloration, roughness and wrinkling. The chemicals cause the skin to lose its outer layer, or peel off, revealing a fresher-looking layer of skin. Known as chemical exfoliation, the procedure is done in doctors' offices so that doctors can control the process and prevent deep skin burns from the highly acidic solutions.
Basically, hydroxy acids penetrate the top layers of the skin, epidermis and upper dermis, to achieve exfoliation (sloughing of old skin cells). Exfoliation stimulates the skin and healthy cells are regenerated. The effect essentially is "anti-aging." The skin is smoother and softer with an overall lessening of fine wrinkles and skin discoloration. The hydroxy acids are also used to improve scaling, precancerous growths (actinic keratoses) on sun-damaged skin. In addition, there is also great benefit with acne. Dead skin cells are exfoliated, opening the pores. Since hydroxy acids are in an infinite array of products, how does one choose the correct formulation for his or her skin condition? The following is a brief explanation of the advantages in each category:
Alpha hydroxy acids derive their name from the molecular composition of the acid. These products include the subcategories of glycolic, malic and citric acids. These acids dissolve easily in water and can penetrate readily into the epidermis and upper dermis. The overall effect is upper skin exfoliation. Oily skin must be cleansed prior to application in order for these acids to be effective.
Beta hydroxy acids, namely salicylic acids, are also named from the molecular composition of the acid. These acids are unique in that they are readily absorbed by the fat properties of the skin. Skin is composed of water and fat molecules that limit penetration from the outside. Different from alpha hydroxy acid, this acid is unique in that it can penetrate into the pores of the skin. This helps clear the pores and exfoliate the skin. Beta hydroxy acid also has anti-inflammatory properties that result in less irritation, burning and stinging.
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.