Identification
Alpha hydroxy acids and beta hydroxy acids are organic acids that occur naturally in nature. Common alpha hydroxy acids, according to the U.S. Food and Drug Administration, are glycolic acid and lactic acid. Beta hydroxy acids include salicylic acid, which is chemically similar to aspirin, and tropic acid. These acids can all be found in fruits that contain sugar. Because they are mildly acidic, they are sometimes used to naturally adjust the pH (a measure of how acidic or alkaline a substance is) of cosmetic products. They are also often included in skin rejuvenation creams and ointments that utilize the exfoliation properties of these acids.
Skin Physiology
The skin on our body is complex and has many layers. The outer-most layers of the skin are often comprised of dead cells. This helps seal moisture in the body, but it also serves as a natural barrier against sunlight, chemical burns, and physical trauma. Because the outer-most layers of the skin absorb so much damage, they must be frequently replaced. At the very base of the skin are stem cells, which constantly divide to make new skin cells. As skin cells get older, they are pushed up to the surface by the newly formed cells behind them. This means that there are always many layers of skin cells, with the older and damaged ones present at the surface.
Organic Acids and Skin Care
The reason why alpha hydroxy and beta hydroxy acids are commonly used in skin rejuvenation products is that they cause mild chemical burns to the upper layers of the skin. The Mayo Clinic explains that these burns cause the older skin layers to fall off, allowing the younger cells to come to the surface. These younger cells are healthier, sometimes reducing the appearance of wrinkles or unusually pigmented areas on the skin. The downside of removing the outer layers of skin is that it exposes the underlying skin to more UV rays from the sun, which can cause sunburn to occur more easily. Because these organic acids are somewhat caustic, they can also cause chemical burns and irritation if applied in high concentrations or for extended periods of time.
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