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Glycolic Skin Care - What is glycolic skin care, and how does it work?

acid hydroxy concentrations alpha

2-Hydroxyethanoic acid, or hydroxyacetic acid, is the chemical name of the smallest possible α-hydroxy acid. An α-hydroxy acid is a carboxylic acid with a hydroxyl group attached to the carbon next to the carboxyl group. They are a well-known class of synthetic building blocks in organic chemistry, useful in the production of various esters and in promoting long chain polymerization. They are used in dyes, inks and paints to adjust flow and gloss characteristics, and even as degreasers and rust removal agents.

If that all sounds dangerously like more industrial chemistry than you ever needed (or wanted) to know, then welcome to the club. But the fact is that you probably already know a good deal more about α-hydroxy acids than you think you do. Have you heard of “chemical peels” which remove wrinkles and make your skin appear newer, and younger? Those, for the most part, are various concentrations and blends of α-hydroxy acids, usually called AHAs by the cosmetics industry.

The most well-known AHA is probably glycolic acid, officially called 2-Hydroxyethanoic acid. It is a naturally occurring product and can be isolated from sugar cane, beets or pineapple. In nearly all practical applications, however, the glycolic acid used in the cosmetics industry is synthetically produced through the reaction of chloroacetic acid with caustic soda. Other well-known AHAs which have been used in cosmetics are lactic acid (which can be obtained from sour milk or yogurt), malic acid (which occurs naturally in apples), citric acid (which occurs in citrus fruits such as oranges) and tartaric acid (which can be isolated from wine and grapes). These materials form the basis of beauty tricks such as milk baths and the application of fruit purees to the skin.

Glycolic acid is the most common AHA in chemical peels because it is the smallest possible α-hydroxy acid. Small molecular size is an important factor in determining a chemical’s ability to penetrate the skin’s outer layer. The small molecular size of glycolic acid enables it to penetrate the outer layer of skin, where its acidic nature then weakens the underlying lipids which hold dead skin cells to our body’s surface. This allows the dead cells to essentially be “peeled” away, revealing the live, more youthful appearing skin underneath. We call this process exfoliation. Glycolic acid is usually mixed with added moisturizers, which it draws with it into the exfoliated skin’s surface, keeping the newly uncovered skin layer from drying out too quickly. Other additives work to carry away the loosened dead skin and neutralize the acid once it has done its job.

Larger AHAs, such as lactic acid, are also used, although they do not penetrate the skin as easily or as deeply. They are said to produce “lighter” peels. The famous Egyptian Queen Cleopatra is said to have regularly bathed in rancid goat’s milk to enhance the beauty of her skin. The penetrating and exfoliating action of AHAs may provide a rationale for that tale, although the effects would have to be startling indeed to justify a dip in rancid milk!

Because it penetrates more deeply, a glycolic acid peel is considerably more abrasive than a lactic acid peel. Most exfoliating creams which use glycolic acid also incorporate other additives that are designed to moderate the action of the glycolic acid, either by reducing its concentration (and thus its acidity), delaying its effects, or by moderating the irritation which may develops immediately after use.

Most over the counter products contain glycolic acid concentrations of 5-10%. These concentrations are considered to be mild, and facilitate exfoliation of only the outermost layers of skin. They are considered safe to use on a daily basis by everyone except people with extremely sensitive skin. Some new formulations also contain certain amino acids which are thought to slow the activity of the glycolic acid, acting almost as a time-release agent.

At concentrations between 10 – 50%, the exfoliating effects are much more pronounced. Applications in this concentration range are typically applied in preparation for even deeper and more abrasive chemical peels. In even higher concentrations, typically between 50 – 70%, the direct supervision of a physician is required and the application is limited to about 5 minutes.

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