Updated: Nov 6, 2009
Since the days of ancient Egypt, people have been using chemexfoliation methods, also known as chemical peeling, to rejuvenate skin. The original chemexfoliant was lactic acid, an active ingredient of sour milk that was used topically by the nobles as 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 chemexfoliants are known to contain alpha hydroxy acids, which are the active ingredients responsible for the skin exfoliation.
Chemical peelings represent accelerated exfoliation or skin damage induced by caustic agents that cause controlled damage, followed by the release of cytokines and inflammatory mediators, resulting in thickening of the epidermis, deposition of collagen, reorganization of structural elements, and increases in dermal volume. This process decreases solar elastosis and replaces and reorients the new dermal connective tissue. The result is an improved clinical appearance of the skin, with fewer rhytides and decreased pigmentary dyschromia.
Modern day chemical peeling originally was promoted by dermatologists, such as P.G. Unna, who first described the properties of salicylic acid, resorcinol, phenol, and trichloroacetic acid (TCA). Slowly, the early practitioners of chemical peels began to develop other peeling agents for varying depths of penetration. In the 1960s, Baker and Gordon developed a deep peeling agent, which was able to smooth deeper furrows, especially around the mouth. From the 1980s to the present, an explosion has occurred in the mass of research on this subject, with the elucidation of many different types of peels, each for a specific range of problems.
The most common agents used for chemical peels are salicylic acid, glycolic acid, 30% salicylic acid in ethanol, 60% pyruvic acid in ethanol, resorcinol, and 10-50% resorcin paste, depending on the problem being addressed. For medium-depth peeling, the most common agents include 60% pyruvic acid applied for 3-5 minutes, 35-50% TCA, 35% TCA augmented with carbon dioxide, Jessner solution plus 35% TCA, and 70% glycolic acid plus 35% TCA. For deep chemical peels, agents include 88% phenol and Baker-Gordon phenol formula.
Coagulation and inflammation
The healing process after a chemical peel must be as rapid as possible to avoid infections that may deepen the wounds, extending the peel from superficial to deep, with increased risks of scaring. Deep peels may be prophylactically treated with antimicrobials, but superficial and medium-deep peels are simply kept moist with the application of petrolatum-based products. After reepithelialization, and when skin appearance is back to normal, a regimen of alpha hydroxy acids, retinoic acid, bleaching creams, moisturizers, and sunscreens should be restarted. Sun exposure must be avoided for 6 weeks after the peel to minimize the risks of postinflammatory hyperpigmentation.
Production of controlled chemical burns of the epidermis and/or dermis results in exfoliation. The first phases of this process must be understood well to control the depth of penetration of chemical peelings. Phases are as follows:
The process of performing a chemical peel
An evaluation of the patient by the clinician is necessary to determine the appropriate treatment based on the dermal defect. When evaluating the patient before the peel, an extensive history should be taken. If it is determined that a chemical peel is warranted, the appropriate agent is selected based on the patient's Fitzpatrick skin type and Glogau photoaging group, as well as other variables that may affect peel penetration. Evaluation of the skin should also refer to skin thickness and oiliness. Sebaceous skin usually requires priming with topical retinoids or/and alpha hydroxy acids and thorough skin defatting before the procedure to assure even penetration of the peeling solution.
The patient must be educated concerning the chemical peel process and give signed consent is advised if performing a medium or deep peel. The patient has to be questioned about their general health status, medications (eg, oral isotretinoin), smoking, previous cosmetic procedures (eg, surgical lifts, fluid silicone injections), recurrent herpetic outbreaks, and keloid formation.
The skin should be defatted properly with acetone. Delicate areas that need to be protected should have petroleum jelly applied, including the lips, inside the nose, and optionally in the nasolabial fold, medial canthus, and lateral canthus. The correct peeling agent then is applied for the appropriate amount of time. When performing a combination peel, pouring one agent at a time is advisable because of the ease in which the agents may be confused when poured into similar cups. Then, the peeled area should be neutralized, and the patient should be sent home with proper instructions along with advice to call should any complications arise. Skin preparation with bleaching creams and early reintroduction of these products in the immediate postpeel period are crucial to avoid postinflammatory hyperpigmentation in dark phenotypes.
Acne
Epidermal growths
Chemical peels are divided into 3 categories depending on the depth of the wound created by the peel. Superficial peels penetrate the epidermis only, medium-depth peels damage the entire epidermis and papillary dermis, and deep peels create a wound to the level of the midreticular dermis. The depth of the peel is dictated by a number of factors, including the chemicals applied and their concentration, mode of application, and skin type and its condition. In general, the depth of the peel determines the patient's inconvenience during and after the procedure, the healing time, the rate of the potential adverse effects, and the results.
Patient history
History is taken to determine the amount of sun-induced damage, history of hypertrophic scarring or keloid formation, and a general medical history. Items of interest include a history of prior surgeries, dermabrasion, or recent laser therapy. In addition, medicines, such as isotretinoin, need to have been stopped for at least 6 months prior to chemical peeling.
Peeling agent concentration
Peeling agent concentration can vary, even though the label indicates the same concentration. The different methods used to determine the concentration of an acid can produce some variation. From strongest to weakest, these methods are dilutions of a saturated solution, the weight-to-weight method, the weight-to-volume method, and grams of acid crystal mixed to 100 mL of water.
Free acid availability
Molecules found in chemical peels are either alcohols that contain a carboxyl (-COOH) and hydroxyl (-OH) groups or regular acids. It has been suggested that according to their chemical properties, substances used in chemical peels are classified as metabolic, caustic, and toxic.
The pH of the agent, or free acid available (pKa), is another measurement. The pKa of the solution is the pH at which half is in acid form; therefore, a lower pKa means that more free acid is available. Many products advertise the acid percentage; however, pKa is a more accurate determinant of strength.
Application of peeling agent
The clinician can vary the number of coats depending on the depth of peel desired. The peel frost, or facial whitening indicating depth of epidermal damage, can aid in the determination of this number.
Frequency that patient receives a peel
Most patients can tolerate a monthly superficial peel, while medium-depth peels can be performed at 6-month intervals if necessary.
Method of application
The peeling agent should be removed from its reservoir and put into a glass bowl. Cotton-tipped applicators may be used individually or put together to deliver more of the agent. Alternatively, 4 X 4-inch gauze may be folded into squares to apply the peeling agent. The gauze has the advantage of directing tactile pressure on the skin surface as the peel is performed. Neutralizing agents are put in metal bowls to distinguish them from the peeling agents. One bowl contains a 1% sodium bicarbonate solution and the other contains cool water. The patient should be resting comfortably in the supine position. The acid should not form pools in the facial folds nor drip from the face. The more acid the clinician applies, the deeper the peel.
Hair is removed from the face with a hair bonnet. The lips are coated with an occlusive ointment preparation, and cotton is put in each ear opening during the peel. If only the face is being peeled, the neck and shoulders are draped with towels. Eyewear is optional and often interferes with the area to be peeled; however, patients must understand that they should keep their eyes closed during the procedure. This is usually not an issue.
Contact time
The duration the peeling agent is in contact with the skin also helps determine the depth of the peel. After the appropriate time has past, neutralization is performed. Some chemical peels, such as salicylic acid and trichloroacetic acid, do not require a neutralization step because the skin neutralizes the acid. Glycolic acid peels must be neutralized. Always wash the patient's face with water following the peel.
Density of adnexal structures
Recent radiation treatment can affect the density of adnexal structures. The reepithelialization process partially occurs from the adnexal structures; therefore, some clinicians advise that a punch biopsy be performed to verify their existence.
Occlusion
Products available, such as biosynthetic occlusive dressings, may decrease pain and speed healing. Examples include hydrogel membrane products, such as Vigilon (Hermal Labs, Delmar, NY); polyurethane membranes, such as Meshed Omiderm (Doak Dermatologics, Fairfield, NJ); and silicone membrane Silon II (BomMed Inc, Bethlehem, Pa).
Rejuvenation regimen
Patients may treat the skin before and after a peel with agents such as tretinoin, hydroquinone, or an alpha hydroxy acid. These may help the skin heal faster and may allow the chemical peel agent to achieve better penetration.
Ointments
Petroleum jelly and other occlusive ointments may, to a minor degree, act as an occlusive barrier.
Defatting
The skin should be cleaned, and excess fat should be removed with agents such as acetone, rubbing alcohol, Septisol, or a combination of these agents. Three parts alcohol with 1 part acetone works well. A thorough defatting of the skin is necessary for proper penetration of the peeling agent because most agents are not lipid soluble.
Application
The patient should sit in a comfortable position, wear a disposable hair cap, and be instructed to keep the eyes closed during the procedure. A zinc oxide past should be applied at the lip and eyelid commissures.
The peeling agent can be applied with 4 X 4-inch gauze, cotton swabs, or the foam applicator that comes with the peel kit. Popsicle sticks are good applicators for the paste form. Apply the peeling agent in cosmetic units, beginning with the forehead and finishing with the chin. Feather the peeling agent into the hairline and the shadow of the mandible. Reapplication of the peeling agent may be necessary if the frost is uneven or is not white enough.
Frost
The change in coloration of the skin to a whitish tint is called frost. This represents the end stage of the chemical peel and shows that keratin agglutination has occurred. Depending on the agent used, the white tint may vary from a brighter white in a superficial peel to a grayish white in a deep peel.
Neutralization
Neutralization of the chemical peeling agent is an important step once the clinician has achieved the proper depth of the peel, which is determined by either the frost or how much time has elapsed. Neutralization can be achieved by applying cold water or wet, cool towels to the face following the frost. This soothes the sharp tingling discomfort caused by the peeling agent. Other neutralizing agents that can be used include bicarbonate spray or soapless cleanser. Peeling agents for which this neutralization step is less important include salicylic acid, Jessner solution, and phenol.
A detailed consent form listing details about the procedure and possible complications should be signed by the patient. The consent form should specifically state the limitations of the procedure and should clearly mention if more procedures are needed for proper results. The patient should be provided with adequate opportunity to seek information through brochures, presentations, and personal discussions. The need for postoperative medical therapy should be emphasized.
Following the peel, the patient must follow the instructions given by the physician to prevent complications. If possible, the patient should stay out of the sun; when unavoidable, the patient should apply a strong sunscreen and wear a hat. An ointment, such as petroleum jelly or bacitracin, should be applied to the involved skin.
The patient should be made aware that the skin will exfoliate and may look cosmetically unattractive for a period of time depending on the depth of the peel. For superficial peels, a follow-up appointment can be scheduled at the time of the next peel. For deeper peels, patients should be seen 2-3 times the week following the peel to provide for early intervention if problems develop.
The patient should be instructed to remain vigilant for signs of infection. If the patient has a history of cold sores, treating the patient with acyclovir (400 mg PO bid) or an equivalent drug is advisable, beginning 2 days prior to the peel and continuing for 7 days after the peel.
Superficial peeling agents
Trichloroacetic acid3,4
Trichloroacetic acid (TCA) can be used to create a superficial, medium, or deep peel. Apart from variables such as patient skin type, adequacy of skin priming, layers of acid applied, and technique of application, the most important factor affecting the depth of the peel is the concentration of TCA used. Concentrations of 10-25% are used for intraepidermal peels, whereas 30-40% are used for papillary dermal peeling. TCA is most commonly used for medium-depth peels, especially to treat pigmentation disorders and early facial rhytides.
TCA (10-35%) has been used for many years and is safe to use at lower concentrations. At higher concentrations, such as 50% and greater, TCA has a tendency to scar and is less manageable than other agents used for superficial peels. TCA is found in several proprietary peels at varying concentrations, and some kits have instructions and buffering agents so the peel can be diluted as deemed necessary. The end point is frosting for TCA peels, which are neutralized either with a neutralizing agent or cold water, starting from the eyelids and then proceeding to the entire face.
Jessner solution
Jessner peel solution 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. Apply the agent, wait for a light frost, and then neutralize with water. The solution is applied to the skin with a soft applicator in patients with thin, sensitive skin or is rubbed in with gauze squares in patients with thick sebaceous skin. The depth of the peel depends on the number of coats of solution applied. A very superficial Jessner peel results in faint erythema, which may be associated with a light powdery-looking whitening of the skin surface.
Salicylic acid
Salicylic acid has been used for several decades and is found in medications such as Whitfield's ointment at 4% and Trans-Ver-Sal at 17% concentrations. Adverse effects, usually only found with high-dose oral ingestion, include headache, nausea, and ringing of the ears, each of which may be resolved with a few glasses of water and rest. These have never been reported with a peel procedure. For salicylic acid peels, the end point is the pseudofrost formed when the salicylic acid crystalizes. This type of agent is very safe, and patients generally tolerate the procedure well.
Salicylic acid is lipid soluble; therefore, it is a good peeling agent for comedonal acne. 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 used today is 20-30% and can be purchased in easy-to-use kits.
A newly introduced agent, beta-lipohydroxy acid, is a salicylic acid derivative and has properties that could possibly expand the clinical use of peels.5,6
Carbon dioxide
Carbon dioxide peels use a solid block of carbon dioxide ice dipped in an acetone-alcohol mixture, which is then applied to the skin for 5-15 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 is at -78°C, while liquid nitrogen is at -196°C.
Alpha hydroxy acid7,3
Alpha hydroxy acid peels include lactic acid, glycolic acid, tartaric acid, and malic acid that are synthesized chemically for use in peels. Various concentrations can be purchased, with 10-70% concentration used for facial peels, most commonly 50% or 70%. Alpha hydroxy acids are weak acids that induce their rejuvenation activity by either metabolic or caustic effect. At low concentration (<30%), they reduce sulfate and phosphate groups from the surface of corneocytes. By decreasing corneocyte cohesion, they induce exfoliation of the epidermis. At higher concentration, their effect is mainly destructive. Because of the low acidity of alpha hydroxy acids, they do not induce enough coagulation of the skin proteins and therefore cannot neutralize themselves and must to be neutralized using water or a weak buffer.
Pyruvic acid
Pyruvic acid is used in superficial peeling and if difficulty is encountered controlling peel depth. A product currently is being developed that uses ethyl pyruvate and has a higher pH and greater buffering ability than other related products.
Medium-depth peels8
Three combination peels currently being used are carbon dioxide and TCA 35%, Jessner solution and TCA 35%, and glycolic 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, more than can be covered in this overview.
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. Again, 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.
Deep peels9
Baker-Gordon peel 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 that produced by laser. This solution is very effective in smoothing wrinkles related to aging and sun damage.
This advantage is countered by several disadvantages. The agent may produce premature ventricular contractions or more serious arrhythmia. A long healing time is required, with erythema occasionally lasting as long as 6 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 is unmatched by the other peeling agents, and, for perioral wrinkles, the phenol peel even surpasses laser resurfacing. Although dramatic results can be achieved with the 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 is made of phenol 88%, 2 mL distilled water, 8 drops Septisol, and 3 drops croton oil. This formula penetrates into the middle reticular dermis and requires special monitoring devices, such as an ECG monitor and pulse oximeter, because of the potential of the phenol to cause arrhythmias. The Baker-Gordon formula is not often used in current practice 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 another 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 a heavier application of Baker-Gordon solution.
Pigmentary change
Pigmentary change is not an uncommon complication, especially with the deeper peeling agents. In some cases, the peeled area remains stark white. Taking proper precautions (as described earlier) can help prevent undesirable pigmentary changes. Usually, patients with lighter complexions have a lower risk of hyperpigmentation, but genetic factors play an important role, and, sometimes, light-skinned patients with "dark genes" hyperpigment unexpectedly. Skin priming using a combination of hydroquinone and tretinoin cream (Kligman formulation) before a superficial or medium-depth peel and early introduction of this preparation after deep peels reduces the rate of this complication.
Scarring
Scarring remains the most dreaded complication of chemical peels. The contributing factors are not well understood. By matching the patient and peeling agent properly, the risk of scarring can be decreased. In addition, to further decrease the risk of scarring, the patient should be advised to refrain from picking at the healing skin. Patients with a history of keloids should not undergo medium or deep peels because of the risk of scarring. Medium and deep peels penetrate to the superficial and reticular dermis and, thus, may stimulate keloids. Weaker superficial peels that only exfoliate the stratum corneum or superficial epidermis can be used.
Infection
By using bacitracin for the medium and deep peels and cleaning the face with a povidone wash, the risk of infection is decreased. Cold sores can be prevented with acyclovir (400 mg PO bid), beginning 2 days prior to the peel and continuing 7 days after the peel. Candidiasis infection also can develop, for which a short course of fluconazole can be used. Cultures need to be taken, and appropriate antibiotics should be administered. Toxic shock syndrome has been reported after a chemical peel.10
Prolonged erythema
Patients usually do not report erythema because it generally subsides in 30-90 days, but sometimes erythema continues. Prolonged erythema is usually not permanent, and topical hydrocortisone can be used to speed the healing process.
Acne
Some patients develop acne after a chemical peel. This usually occurs between days 3-9. Cultures should be taken, and an antibiotic that covers gram-positive bacteria should be prescribed. If it is a true acne occurrence, then the appropriate topical treatment also should be started. If severe enough, isotretinoin may be initiated.
Milia
Small inclusion cysts, sometimes called milia, can appear in the healing process after a chemical peel. These usually appear about 2-3 weeks after reepithelialization and may be aggravated by ointments, owing to occlusion of the sebaceous glands.
Novices at chemical peeling should educate themselves through dermatology conferences, journals, and hands-on training. After sufficient knowledge is obtained, starting with superficial problems, such as acne, general skin rejuvenation, or melasma, using a superficial peel such as 20% salicylic acid, is recommended.
Chemical peels are not a cure-all, and patient expectations should be realistic. Dynamic wrinkles caused by muscle action or sagging due to old age usually requires an alternative treatment, such as facelift, botulinum toxin (BOTOX®), or collagen injections. The clinician should assess each patient, explain the alternatives, and then decide on a course of action. The correct peeling agent needs to be chosen if chemexfoliation is decided. Proper defatting of the skin is critical for an even peel. Application of the peeling agents must be performed correctly. Postpeel instructions need to be explained carefully. If performed correctly, the chemical peel can give excellent results, with many satisfied patients.
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chemical peels, chemexfoliation, peeling agents, chemical abrasion, glycolic acid, trichloroacetic acid, salicylic acid
Gabriella Fabbrocini, MBBS, Tenured Researcher in Cutaneous and Venereal Diseases, Department of Systemic Pathologies, Division of Dermatology and Venereology, Università degli Studi di Napoli Federico II, Italy
Disclosure: Nothing to disclose.
Zoe Diana Draelos, MD, Primary Investigator, Dermatology Consulting Services; Private Practice
Zoe Diana Draelos, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Cosmetic Surgery, American Academy of Dermatology, American Contact Dermatitis Society, American Medical Association, American Society for Dermatologic Surgery, North Carolina Medical Society, Sigma Xi, Society for Investigative Dermatology, and Women's Dermatologic Society
Disclosure: Nothing to disclose.
Michael J Wells, MD, Associate Professor, Department of Dermatology, Texas Tech University Health Sciences Center
Michael J Wells, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, and Texas Medical Association
Disclosure: Nothing to disclose.
Christen M Mowad, MD, Associate Professor, Department of Dermatology, Geisinger Medical Center
Christen M Mowad, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, and Phi Beta Kappa
Disclosure: Nothing to disclose.
Catherine M Quirk, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania
Catherine M Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.
Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors, Raymond T. Kuwahara, MD, MBA, and Ron Rasberry, MD, to the development and writing of this article.
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