What are alpha hydroxy acids?

Alpha hydroxy acids are a group of organic carboxylic compounds that are produced both naturally and industrially. Some natural types of alpha hydroxy acids include:

• Citric acid: found in citrus fruits

• Lactic acid: found in milk and pickles

• Glycolic acid: derived from sugarcane

• Malic acid: found in various apples

• Tartaric acid: found in various grapes

Note: Among the various types of AHA, lactic, citric, and glycolic acids are used in cosmetic products for skin health.

Structure and physical properties of alpha hydroxy acids

There are several types of acids in the alpha hydroxy acid group. In these molecules, one or more hydroxyl functional groups are attached to the alpha carbon (the first carbon next to the acid group). Tartaric acid is a dicarboxylic acid with two hydroxyl groups located at the alpha position. Malic and citric acids have two hydroxyl groups, one of which is attached to a carboxyl group at the alpha position and the other to a carboxyl group at the beta position.

Uses of AHAs

AHAs are best known for their use in cosmetics and personal care products. These acids have many benefits for the skin. They can combat signs of aging, fine lines, dark spots, and even acne due to their various properties, including:

• Increased skin thickness

• Improved quality of elastic fibers

• Increased collagen density

• Skin exfoliation

Alpha hydroxy acids are also effective in reducing solar keratosis, roughness, and discoloration of the skin caused by sun exposure.

At concentrations of ۴ to ۱۰ percent, alpha hydroxy acids are available as creams or other products without a prescription. While pharmaceutical types have concentrations higher than ۲۰ percent and can only be obtained with a doctor's prescription.

Mechanism of action of alpha hydroxy acids

Numerous studies have examined the mechanism of action of alpha hydroxy acids. The results of one study showed that the effects of alpha hydroxy acids when used topically are related to their chelating properties (chelating). This feature of alpha hydroxy acids leads to a reduction in calcium ion concentration in the epidermis and the release of calcium from cell adhesions. In fact, this results in the loss of calcium ions in the cadherins of desmosomes (which are the main components of desmosomes that play an important role in maintaining intercellular adhesion) and adhesive junctions. As a result of the disruption of cell adhesion, exfoliation occurs. Additionally, the reduction of calcium can enhance cell growth by stimulating the epidermis and delay cellular differentiation.

Safety assessment of alpha hydroxy acids in cosmetics

According to the report of the Expert Panel on Cosmetic Ingredient Safety (CIR), which serves as the self-regulatory authority of the cosmetics industry for assessing the safety of cosmetic ingredients, the use of products containing alpha hydroxy acids such as glycolic acid and lactic acid is safe under the following conditions:

• The concentration of AHA in the product should be ۱۰

Alpha hydroxy acids

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