What Are Alpha Hydroxy Acids and How Do They Work?

Alpha-hydroxy acids are naturally occurring acids, derived from the sugars in particular plants. Some examples are Glycolic Acid (Sugar Cane), Lactic Acid (Milk), Tartaric Acid (Grapes), Citric Acid (Citrus Fruits), Malic Acid (Apples), and Mandelic Acid (Bitter Almonds). These acids work at the very base of the stratum corneum, dissolving the cement that holds dead skin cells together. This increases cell turnover and influences the structure of new stratum corneum being made. This results in skin that is more flexible, more smooth, and more even in tone. At greater concentrations (12%-20%), deeper dermal effects, such as higher amounts of mucopolysaccharides and collagen and increased skin thickness, are observed. Eventually, alpha hydroxy acids will produce skin that is softer, smoother, less wrinkled, less dehydrated, and more even in skin tone.

Glycolic Acid

Glycolic acid, the most common alpha hydroxy acid found in cosmetic preparations, is popular mainly because that is the alpha hydroxy acid that has been the most widely studied. The small molecular structure and the rapid penetration of glycolic acid make it the most irritating of the group. The possibility of irritation make glycolic acid more suitable for those with mature or non-sensitive skin. Those with oilier skin types often prefer glycolic acid sinks it sinks into the skin quickly. The widespread use of glycolic acid, though, gives the consumer flexibility on the formula. The consumer has a wide range of choices with glycolic acid products: gels, serums, lotions, creams, formulas at varying pH's and concentrations, for that contain a variety of other age-fighting ingredients. If a person wants to find a cream that contains both AHAs and vitamin C, they will have a good chance of finding a glycolic acid formulation that does.  Buy Ageless Crystal Cream and get a FREE sample size 50% Professional Glycolic Acid Peel Kit

Lactic Acid

Lactic acid is most often found in moisturizers due to its more moisturizing properties. Lactic acid is a natural humectant that draws and holds water in the upper layers of the skin. Alpha hydroxy acids as a whole can increase the skin's ability to trap water due to an increased production of natural skin moisturizers (hyaluronic acid), but lactic acid's extra humectant properties make it even more ideal for treating dry skin.  We use Lactic Acid in our best selling moisturizer Skin Tight . Lactic acid's larger molecule size makes it less irritating than glycolic acid. Also, because lactic acid is naturally found in the human body, it is not likely to cause an allergic reaction in those with reactive skin. Lactic Acid is ideal for those with slightly sensitive, dry skin or allergy-prone skin.  Our Creamy Cleanser contains Lactic Acid to exfoliate, cleanse and moisturize.

Mandelic Acid

Mandelic acid, an alpha hydroxy acid derived from the bitter almond, is not a widely used AHA in the cosmetic industry. It is, however, no stranger to the scientific community. Due to its natural antibacterial properties, mandelic acid is used in oral drugs to help sterilize urine and treat urinary tract infections. This alpha hydroxy acid has some unique characteristics that make it a very promising topical agent, too. With a pKa of 3.41, mandelic acid is a stronger acid than glycolic acid (3.83), yet the large molecule structure and even penetration of mandelic acid make it substantially less irritating than glycolic acid. The gentle nature of mandelic acid reduces the risk of inflammation that can sometimes occur with alpha hydroxy acid use. This quality allows those with sensitive skin, who cannot normally tolerate glycolic acid, to use AHAs - at even higher concentrations. It also makes it suitable for use on darker skin types who are at high risk for postinflammatory hyperpigmentation. The natural antibacterial properties and non-irritating nature of mandelic acid make it the ideal AHA for those trying to treat rosacea or acne.

Malic Acid

Malic Acid, is an acid that is most commonly found in apples. Malic acid, along with tartaric acid, has unique antioxidant properties that none of the above AHAs contain. Along with its antioxidant properties, malic acid has considerable moisturizing properties. Malic acid imparts a very smooth almost slippery consistency to products. When applied to the skin, malic acid leaves a protective, moisturize coat on the skin.

Citric Acid

Citric acid is most often used in cosmetics in a low (2-3%) concentration to adjust the pH of a product. Because we cannot find any products using solely citric acid in high enough concentrations, we do not have much information on the individual properties of this particular AHA. We will eventually conduct a few tests to check for its irritancy level and skin lightening potential.

Tartaric Acid

Tartaric acid appears to be the strongest acid in the group with a pKa of 3.04 ( a difference of 1 unit of pK represents a tenfold difference in strength). It is also one of the few AHA's that has antioxidant properties. We have found a few products that contain tartaric acid, but has only been within an AHA blend.

AHA's at greater bioavailability appear to have dermal affects that influence the formation of collagen. Alpha hydroxy acids, on topical application to photoaged skin, have been shown to substantially increase skin thickness. Skin biopsies revealed increased synthesis of mucopolysaccharides and collagen as well.