Glycolic acid is perhaps the best-known of a group of chemicals called fruit acids or alpha-hydroxy acids (AHA). It is derived from sugar cane, so it can be considered a natural product. Citric acid from oranges and other citrus fruits also fall under the same classification as glycolic acid.

Industrial uses for glycolic acid include rust removal and degreasing, so pure glycolic acid (generally sold in concentrations of 70% or better) is extremely dangerous to exposed skin. In fact, the government considers any product with a concentration of glycolic acid over 10% to be a hazardous material.

Most consumers know glycolic acid not from its industrial uses, but from its cosmetic ones. Glycolic acid is generally used as a natural skin exfoliant and moisturizer, although there is much debate over its safety and effectiveness. Some proponents of glycolic acid suggest that products with a glycolic acid concentrations of less than 10% are practically useless. The problem is that many large-scale cosmetic producers will not increase the glycolic acid levels for fear of liability and class action lawsuits. Some smaller cosmetics companies with high-end clients do offer products with at least a 10% glycolic acid concentration.

Glycolic acid works as an exfoliating agent because of its high acidity but easy solubility. When placed on the skin as part of an exfoliating cream or gel, glycolic acid goes under the damaged upper layers of skin and destroys the 'glue' which holds dead skin to the surface. As this dead skin is chemically burned off, the other ingredients carry the individual flakes away and a water rinse neutralizes the remaining acid. The result is a much-smoother skin surface and a more youthful appearance. A secondary benefit is glycolic acid's ability to draw moisturizers into the newly-exfoliated skin surface. This is why cosmetic counters often sell a complete system of skin care; the rest of the alpha-hydroxy line contains moisturizers and neutralizers to counteract the corrosive actions of glycolic acid.

Cosmetic exfoliants and moisturizers containing glycolic acid may leave the user's skin especially sensitive to the sun, so many skin care experts recommend using a sunscreen after exfoliating with glycolic acid. If a 10% concentration of glycolic acid can cause concern over skin damage, another use may be even more controversial. Some customers seeking a more complete exfoliation may opt for a chemical peel. In general, a chemical peel involves a careful scrubbing of the skin followed by an application of a powerful AHA such as glycolic acid. Concentration levels of glycolic acid in chemical peels can be as high as 50% or more. Even industrial suppliers of glycolic acid limit their concentration to 70%, so this is indeed a very powerful chemical process.

Quite often after a chemical peel, a patient's skin will look as if it were extremely sunburned. Several days of recovery are often necessary for a complete recovery from a glycolic acid peel. Proponents of glycolic acid say that the process may appear dangerous or unsightly, but the results are worth the temporary discomfort.

Whether or not glycolic acid is the miracle ingredient in a cosmetic Fountain of Youth, there can be no doubt that it is effective when used correctly and in the proper concentration level for an individual's exfoliating and moisturizing needs. As with any other acid, proper attention must be given to storage and access. Young children could experience severe skin rashes or internal problems if the products are improperly applied or ingested.