Glycolic acid

Overview
Glycolic acid (or hydroxyacetic acid) is the smallest α-hydroxy acid (AHA). It appears in the form of a colorless, odorless and hydroscopic crystalline solid that is highly soluble in water and related solvents. Glycolic acid is associated with sugar-crops and is isolated from sugarcane, sugar beets, pineapple, canteloupe, and unripe grapes.

Uses
Due to its excellent capability to penetrate skin, glycolic acid finds applications in skin care products, most often as a chemical peel performed by a dermatologist in concentrations of 20%-80% or at-home kits in lower concentrations of 10%. It is used to improve the skin's appearance and texture. It may reduce wrinkles, acne scarring, hyperpigmentation and improve many other skin conditions. Once applied, glycolic acid reacts with the upper layer of the epidermis, weakening the binding properties of the lipids that hold the dead skin cells together. This allows the outer skin to "dissolve" revealing the underlying skin.

Glycolic acid is also a useful intermediate for organic synthesis, in a range of reactions including: oxidation-reduction, esterification and long chain polymerization. It is used as a monomer in the preparation of polyglycolic acid and other biocompatible copolymers (e.g. PLGA). Among other uses this compound finds employment in the textile industry as a dyeing and tanning agent, in food processing as a flavoring agent and as a preservative. Glycolic acid is often included into emulsion polymers, solvents and additives for ink and paint in order to improve flow properties and impart gloss.

Preparation
Glycolic acid is isolated from natural sources and is inexpensively available. It can be prepared by the reaction of chloroacetic acid with sodium hydroxide followed by re-acidification.

Safety
Glycolic acid is a mild irritant.