A chemical peel refers to a controlled removal of varying layers of the epidermis and superficial dermis with the use of a wounding agent, such as phenol or TCA. Chemical peels can be subdivided into the types of wounding agents used and the depth of the peel, either epidermal or dermal.
Since the days of ancient Egypt, chemoexfoliation methods also known as chemical peeling has been used to rejuvenate skin. The original chemoexfoliant was lactic acid, an active ingredient of sour milk that was used topically by the nobles as a part of an ancient skin rejuvenation regimen.
In the Middle Ages, old wine with tartaric acid as its active ingredient was used for the same purpose. Today, these historical chemoexfoliants are known to contain alpha-hydroxyl-acids, which are the active ingredients responsible for skin exfoliation.
The chemical peel produces a controlled partial thickness injury to the skin. Following the insult to the skin, a wound healing process ensues that can regenerate epidermis from surrounding epithelium and adnexal structures, decrease solar elastosis (seen histologically in the sun-exposed skin of the elderly or in those who have chronic actinic damage), and replace and reorient the new dermal connective tissue. The result is an improved clinical appearance of the skin, with fewer rhytides (wrinkles) and decreased pigmentary dyschromia (abnormal color).
Modern day chemical peeling originally was promoted by dermatologists, such as P.G. Unna, who first described the proprieties of salicylic acid, resorcinol, phenol, and TCA. Slowly, the early practitioners of chemical peels began to develop other peeling agents for varying depths of penetration.
Superficial Peeling Agents (Epidermal Peels)
- Trichloroacetic acid (TCA) (10-35%) has been used for many years and is safe to use at lower concentrations. At higher concentrations of 50% and above, TCA has a tendency to scar and is less manageable than other agents used for superficial peels found in several proprietary peels at varying concentrations.
- Jessner’s peel is a combination of salicylic acid 14%, lactic acid 14%, and resorcinol 14% in alcohol. This agent is easy to use with no timing necessary.
- The agent is applied to the face.
- When a light frost forms on the skin.
- Neutralize with water.
- Salicylic acid has been used for several decades and is found in medications, such as Whitfield’s ointment at 4%, and Ver-Sal at 17% concentrations. Salicylic acid is lipid soluble; therefore, it is a good peeling agent for comedonal acne (necrotizing). The salicylic acid is able to penetrate the comedones better than other acids. The anti-inflammatory and anesthetic effects of the salicylate result in a decrease in the amount of erythema and discomfort that generally is associated with chemical peels. The most common concentration today is 20% to 30%.
- Carbon dioxide, when used for a chemical peel, uses a solid block of carbon dioxide ice dipped in an acetone-alcohol mixture and then applied to the skin for 5 to 15 seconds, depending upon the desired depth. Carbon dioxide is easier to use, and the depth of the peel can be controlled more easily than with liquid nitrogen. Carbon dioxide has a temperature of 78ْ degrees Celsius while liquid nitrogen has a temperature of 196ْ degrees Celsius.
- Alpha-hydroxy-acid peels include lactic acid, glycolic acid, tartaric acid, and malic acid that are synthesized chemically for use in peels. Various concentrations are available, with 10% to70% concentrations used for facial peels, most commonly 50% or 70%.
Medium-Depth Peels (Epidermal or Dermal)
- Three combination peels currently being used are carbon dioxide and TCA 35%, Jessner’s and TCA 35%, and glycolic acid and TCA 35%. These peels are as effective as the other medium-depth peels with less chance of scarring and pigment dyschromia. An endless number of combinations are possible. TCA 50% is seldom used because of a higher risk of scarring and the availability of the combination peels.
- Full strength phenol (88%) is a very caustic agent that causes immediate keratin agglutination, preventing further penetration of the agent deeper into the dermis. The increased risk of scarring and pigment dyschromia makes this agent less attractive to the practitioner. If diluted and mixed with other complementary chemicals, this agent can be used effectively as a deep peeling agent.
- Pyruvic acid is rarely used today because of its fast action which causes difficulty in controlling the depth. A product currently is being developed that uses ethyl pyruvate and has a higher pH and greater buffering ability than other related products.
Deep Peels (Dermal Peels)
The Baker Gordon peel (phenol 88%, 2ML distilled water, 8 drops Septisol, and 3 drops croton oil) produces the most dramatic results and is the most effective peeling agent currently used. The phenol produces a new zone of collagen that is thicker than produced by laser. The solution is very effective in smoothing wrinkles related to aging and sun damage.
- This advantage is countered by several disadvantages. A long healing time is required, with erythema occasionally lasting as long as six months. In addition, the potential for pigmentary changes, scarring, and infection are high with this peel. Despite the problems that may be encountered, a properly administered phenol peel has had better results than other peeling agents, and for perioral wrinkles, the phenol peel even surpassed laser resurfacing. Although dramatic results can be achieved with a phenol peel, the risks and benefits should be weighed carefully before proceeding. Only experienced clinicians should attempt a phenol agent based peel.
- The Baker Gordon solution penetrates into the middle reticular dermis and requires special monitoring devices, such as an electrocardiogram (ECG) monitor and oximeter, because there is a potential that phenol may cause arrhythmias. This formula is seldom used because of resurfacing laser technology; however, a deep peel works well on deep perioral rhytides. Deep peels can be occluded or nonoccluded. The occluded method uses zinc oxide tape or other artificial barrier product to prevent evaporation of the phenol from the skin, thus enabling the solution to penetrate deeper. (Two variants of the Baker Gordon peel are Litton's formula, which replaces Septisol with glycerin, and the Beeson McCollough formula, which uses aggressive defatting and heavier application of Baker Gordon solution.)