Answer:
Glycolic acid is a subtype (monohydroxycarboxylic) of the alpha-hydroxy acid (AHA) peels, which include naturally occurring acids such as lactic acid, citric acid and tartaric acid. The peel depth is determined by the agent, its concentration, the volume applied, time of contact, frequency of application, integrity of the stratum corneum, skin thickness, cleansing, oiliness and post-peel care. AHA's increase the production of collagen, the skin's water content, and GAG's. They result in increased number of elastin fibers, increased volume of the epidermis, and tightening of the superficial skin layers. Glycolic acid has the smallest molecular structure and therefore penetrates more readily and is more active. Decreased pH produces an increased effect because of better bioavailability but also produces more skin irritation. AHA's are beneficial in the treatment of acne scars, dry skin, hyperkeratosis, hyperpigmentation, and environmentally wrinkled skin.
The pre-peel program is crucial for the success of the peel and also indicates patient compliance. Home AHA preparations have a maximal concentration of 10% and pH greater than 3.5%. AHA can be combined with bleaching agents in Fitzpatrick II, III, IV and V patients to decrease the chance of postinflammatory hyperpigmentation, and tretinoin (Retin-A). The technique of the peel itself is similar to other peels. Unlike other peels, the depth is time dependent. To stop the peel, it must be neutralized with water. Post-peel care consists of sunblock for more superficial peels and an emollient until crusting resolves. Patients with a history of herpes must be on an antiviral (Zovirax, Famvir) by the time re-epithelialization occurs (usually started the day of the peel). After crusting resolves, the patient may resume the pre-peel regimen. A superficial peel (superficial papillary dermis - 0.06mm) can be performed weekly, a medium depth peel (papillary or reticular dermis - 0.5mm) every 6 to 12 months, and a deep peel (mid-reticular dermis - 0.6mm) rarely more than once.