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 milk (lactic acid) to improve her complexion. Now hydroxy acids are a common additive to numerous skin care products, including moisturizers, cleansers, toners and masks.
Alpha hydroxy acids are derived from fruit and milk sugars. The most commonly used alpha hydroxy acids are glycolic acid and lactic acid because they have a special ability to penetrate the skin. They also have the most scientific data on their effectiveness and side effects. The following are the five major types of alpha hydroxy acids found in skincare products and their sources:
Alpha hydroxy acids work mainly as an exfoliant. They cause the cells of the epidermis (the top layer of the skin) to become "unglued" allowing the dead skin cells to slough off, making room for regrowth of new skin. Alpha hydroxy acids may even stimulate the production of collagen and elastin.
Alpha hydroxy acids are reported to improve wrinkling, roughness and mottled pigmentation of photodamaged skin after months of daily application.
Alpha hydroxy acids found in skincare products work best in a concentration of 5 to 8 percent and at a pH of 3 to 4.
The two major side effects of alpha hydroxy acids are irritation and sun sensitivity. Symptoms of irritation include redness, burning, itching, pain and possibly scarring.
People with darker colored skin are at a higher risk of scarring pigment changes with alpha hydroxy acids. The use of alpha hydroxy acids can increase sun sensitivity by 50 percent, causing an interesting dilemma.
It appears that alpha hydroxy acids may be able to reverse some of the damage caused by photoaging, but at the same time, they make the skin more susceptible to photoaging. It is clear that anyone using alpha hydroxy acids must use a good sunscreen that contains UVA and UVB protection. Note that many sunscreens do not protect against UVA rays, the rays most implicated in skin aging.
Because of concerns over the side effects of alpha hydroxy acids, the FDA in 1997 announced that alpha hydroxy acids are safe for use by consumers with the following guidelines:
Alpha hydroxy acids in various concentrations are used in chemical peels. These chemical peels give results that are similar to microdermabrasion—erasing fine lines and giving the skin a smoother appearance with one to three applications.
These treatments must, however, be repeated every three to six months to maintain this skin appearance. Doctors can use alpha hydroxy acid products that have a concentration of 50 to 70 percent. Alpha hydroxy chemical peel treatments also erase fine wrinkles and remove surface scars, but the effects last longer—up to two to five years.
The higher the alpha hydroxy acid concentration used in a chemical peel, the more skin irritation occurs. At the 50 to 70 percent concentration, a person could expect to have severe redness, flaking and oozing skin that can last for 1 to 4 weeks.
There is only one beta hydroxy acid: salicylic acid.
The main difference between alpha hydroxy acids and beta hydroxy acid is their lipid (oil) solubility. Alpha hydroxy acids are water soluble only, while beta hydroxy acid is lipid (oil) soluble. This means that beta hydroxy acid is able to penetrate into the pore, which contains sebum, and exfoliate the dead skin cells that are built up inside the pore.
Because of this difference in properties, beta hydroxy acid is better used on oily skin with blackheads and whiteheads. Alpha hydroxy acids are better used on thickened, sun-damaged skin where breakouts are not a problem.
Alpha hydroxy acids are found in a variety of skincare products, including moisturizers, cleansers, eye cream, sunscreen, and foundations. However, it is best to pick one product that contains the proper formulation of alpha hydroxy acid to use as your exfoliant, and then choose other skin care products or cosmetics that don't contain alpha hydroxy acids to reduce the likelihood of skin irritation.
Using an alpha hydroxy acid in a moisturizer base may be the best combination of products. Cleansers containing alpha hydroxy acids are not very effective because the alpha hydroxy acid must be absorbed into the skin to work. Cleansers are washed off before this absorption occurs.
Sunscreen must be applied liberally when using an alpha hydroxy acid product. The sunscreen should have an SPF of at least 15 for UVB protection and contain avobenzone, titanium dioxide or zinc oxide for UVA protection.
Alpha hydroxy acids work best in a concentration of 5 to 8 percent and at a pH of 3 to 4. Unfortunately, cosmetic manufacturers are not required to provide concentration information on the label. As a general rule of thumb, having the alpha hydroxy acid listed as the second or third ingredient on the list makes it more likely that it contains the proper concentration. The only way to know for sure the pH of a product is to test with a pH strip.
Alpha hydroxy acids as a component in moisturizers, creams, or other skin care products may reverse some of the damage caused by photoaging. In the form of a chemical peel, especially at higher concentrations in a doctors office, these acids may improve the appearance of fine wrinkles and scars for up to a few years. Alpha hydroxy acids tend to work better for people with thickened, sun damaged skin, whereas beta hydroxy acids may be a better choice for those with acne prone skin.
Despite their ability to improve the appearance of sun damaged skin, alpha hydroxy acids can also increase sun sensitivity and increase the risk of skin damage with sun exposure. Wearing a good sunscreen which includes coverage for both UVA and UVB rays is important if you choose to use these products.
Tran, D., Townley, J., Barnes, T., and K. Greive. An Antiaging Skin Care System Containing Alpha Hydroxy Acids and Vitamins Improves the Biomechanical Parameters of Facial Skin. Clinical, Cosmetic and Investigational Dermatology. 2014. 8:9-17.