superficial and medium-depth chemical peels

Clinics in Dermatology (2008) 26, 209–218

Superficial and medium-depth chemical peelsEileen Clark, MD, Lawrence Scerri, MD⁎

Department of Dermatology, University of Malta, Sir Paul Boffa Hospital, Floriana, Malta

Abstract The use of chemicals for facial rejuvenation has been explored since ancient times. A soundknowledge of skin anatomy and wound healing is important for understanding the principles ofchemical peeling. Chemical peels are classified according to the depth of skin resurfacing produced. Themain clinical indications in the cosmetic field are photoaging, dyschromias, and acne scars, which areclassified according to the histologic depth of the clinical changes. Proper patient selection, skinpriming, and postpeel care are of utmost importance in ensuring a satisfactory outcome. Chemical peelsare combined with other rejuvenating treatments for best results in photoaging.© 2008 Elsevier Inc. All rights reserved.

Introduction

Facial resurfacing techniques are used for the reversal ofsigns of skin aging and for the treatment of certain epidermalcutaneous lesions as well as scars, particularly acne scars.Various resurfacing modalities exist to suit the different skintypes and associated conditions and range from superficial todeep. The main currently practiced skin resurfacingtechniques are chemical peeling, classic dermabrasion,microdermabrasion, and ablative lasers. As a rule, the riskof procedure-related morbidity increases with the depth ofresurfacing, although there is also an operator-dependentelement. It is recommended to combine chemical peelingwith other skin rejuvenating and resurfacing techniques forbest overall results.

Historical aspects of skin resurfacing

The use of chemicals for facial skin softening andrejuvenation has been explored since ancient times. Chemi-

⁎ Corresponding author. Tel.: +356 22987127; fax: +356 22987131.E-mail address: [email protected] (L. Scerri).

0738-081X/$ – see front matter © 2008 Elsevier Inc. All rights reserved.doi:10.1016/j.clindermatol.2007.09.015

cal peeling may be the oldest cosmetic procedure performedthat is still in use today. Four thousand years ago, Egyptiansdescribed a method of treating the skin with abrasive masksof alabaster particles. Cleopatra bathed in sour milk, whereaswomen in ancient Rome rubbed fermented grape skins fromthe bottom of wine barrels over their skin to enhance theirbeauty, unknowingly benefiting from the superficial exfo-liative effects of the hydroxyl acids: lactic acid in milk andtartaric acid in grape skins. These acids are now commoningredients of many beauty products.1

Later in history, poultices containing mustard, sulfur, andlimestone were used for similar purposes. Indian womenmixed urine with pumice, and Turkish women singed theirskin with fire to create a superficial form of exfoliation.Dermabrasion was also popularized in ancient Egypt, wherephysicians used sandpaper to treat scars.

The evolution of chemical peeling and dermabrasion intothe procedures commonly used today began in the early 20thcentury by cosmeticians, and formulas were closely guardedsecrets. In 1905, Kromayer pioneered surgical planing, todayknown as dermabrasion.2 He is reported to have usedrotating wheels and rasps for the treatment of keratosis, acnescars, and pigmentary disorders. In the post–World War IIera, many attempts were made to improve traumatic tattooinjuries sustained in the war, and standardized dermabrasion

210 E. Clark, L. Scerri

procedures were developed in the early 1959s by Dr Kurtin,3

a physician, and Mr Noel Robbins,4 an engineer.At the turn of the 20th century, Mackee, a dermatologist,

used phenol to treat acne scars.5 Scientific investigations onthe use of phenol and trichloroacetic acid (TCA) peels forfacial resurfacing, however, only began in the late 1950sand 1960s, and TCA peels did not really become popularuntil late 1980s. This was partly related to the diminishedinterest in the treatment of photoaging in the immediatepostwar period as compared with the treatment of war-related injuries.1 Also, earlier results of chemical peels werenot uniformly good because there was no proper skinpriming before the procedure, and the use of maintenancetherapy posttreatment was lacking. It was not until 1972 thatBaker and Gordon6 demonstrated the beneficial resultsachieved with phenol to a group of plastic surgeons. Plasticsurgeons and dermatologists have now delineated indica-tions and limitations of chemical peels and improved theirsafety and efficacy.

Chemical peels

Skin anatomy

A sound knowledge of skin anatomy and normal woundhealing is important for understanding the principles ofchemical peeling. The skin covers the entire external surfaceof the body, and its functions include protection, sensoryperception, immunologic surveillance, thermoregulation,and control of insensible fluid loss.

The skin is composed of the epidermis and dermis, whichlie on the subcutaneous fat layer. Because the epidermis isdevoid of blood vessels, it depends on the dermis for itsnutritive supply and removal of waste through the dermoe-pidermal junction. The function of the dermis is primarily tosustain and support the epidermis.

Epidermal appendages, including sebaceous glands,sweat glands, apocrine glands, and hair follicles, developas downward growths from the epidermis deep into thedermis. They are lined with epithelial cells that have thepotential for division and differentiation. They are thereforean important source of cells for re-epithelialization when theoverlying epidermis is destroyed. Such destruction of theepidermis may occur in partial-thickness burns and traumaticabrasions; iatrogenically in chemical peeling, dermabrasion,and other skin resurfacing techniques; or in split-thicknessskin graft harvesting. The face has a particular ability to re-epithelialize deep cutaneous wounds because it has a veryhigh concentration of sebaceous glands, which can also befound in the subcutaneous fat layer.7

The regeneration of the epidermis from the epidermalappendages located in the remaining dermis begins within24 hours of wounding, and it is usually complete in 7 to10 days. The new epidermis shows greater organization and

vertical polarity, with the disappearance of actinic keratosisand lentigines. There is a thinner, more compact stratumcorneum, associated with a thicker, acanthotic epidermiswithout atypia and with a uniform dispersion of melanin.New collagen and glycosaminoglycan deposition in thedermis is also stimulated to give a tighter and firmerappearance to the skin. Dermal regeneration is a slowerprocess, but it is usually complete within several months.8,9

Definition and classification of chemical peels

Chemical peeling is the process of applying chemicals tothe skin to destroy the outer damaged layers, thusaccelerating the normal process of exfoliation. Differentagents have different depths of penetration, and therefore,chemical peels can be divided into 4 different groups basedon the histologic level of necrosis that they cause10:

1. Very superficial (exfoliation): destruction of the
stratum corneum without creating a wound belowthe stratum granulosum;
2. Superficial (epidermal): destruction of part or all of the
epidermis, anywhere from the stratum granulosum tothe basal cell layer;
3. Medium (papillary dermal): destruction of the epider-
mis and part or all of the papillary dermis; and
4. Deep (reticular dermal): destruction of the epidermis
and papillary dermis, extending into the reticulardermis.
This classification helps predict which skin abnormalitieswill be corrected by the particular chemical peel according tothe histologic level of the peel. It also helps predict the effectthe peel will have on a patient's lifestyle. A very superficialexfoliation does not hinder the patient's lifestyle, but amedium depth peel will cause erythema, edema, andpigmentation for about a week after the procedure. Theassociated risks of complications can also be predictedbecause these increase with the depth of the peel.

Clinical indications for chemical peels in thecosmetic field

Dyschromias and wrinkles are the major clinical indica-tions for facial chemical peeling. Most wrinkles anddyschromias are due to photodamage combined with thenormal aging process of the skin.

PhotoagingThe term photoaging refers to the skin changes that are

associated with chronic UV light exposure. The clinical signsof photodamaged skin include markedly increased skinroughness, mottled hyperpigmentation, loss of elasticity,wrinkling, and the development of solar lentigines andactinic keratosis. The histologic changes in the epidermis of

211Superficial and medium-depth chemical peels

photoaged skin are thickened stratum corneum with a thinneratrophic epidermis, epidermal atypia, and irregular disper-sion of melanin. Epidermal dysplasia corresponds to thedevelopment of actinic keratosis and may result in thegrowth of basal or squamous cell carcinomas. In the dermis,glycosaminoglycans are decreased, and the elastic fibersdegenerate. Collagen is also lost, and the relative proportionof Type I to Type III collagen is reduced.1,11

Dyschromias and wrinklesDyschromias include ephelides (freckles), lentigines

simplex, senile lentigines, flat seborrheic keratoses, nevi,melasma, and postinflammatory hyperpigmentation.12

Wrinkles may be divided according to severity.13 Finewrinkles or crinkles are presumably due to thinning of theepidermis and upper dermis, creating a “cigarette paper” typeof tissue, and often appear as crosshatched lines. Muscle-related wrinkles are caused by repetitive movements thatcreate a dent in the epidermis and most of the dermis.Accordion-pleat wrinkles are due to loose redundant skinwith atrophy of the epidermis, dermis, and subcutaneoustissue, as well as loss of elasticity. Folds are due to downwardsagging of the skin and underlying muscles that is causedby gravity.

Classification of photodamaged skin14

The classification of photodamaged skin by Rubin14 isbased on the histologic depth of visible clinical changes,making the choice of the appropriate type of depth specifictreatment easier. It also helps predict the morbidityassociated with the treatment program and the complicationsrisk level.

Level 1 Clinical signs are due to alterations in the
epidermis only. Most abnormalities are of pigmentationand texture, including freckles, lentigines, and a dullrough skin texture due to the increased thickness of thestratum corneum.
Level 2 Clinical signs are due to the epidermis and
papillary dermis and are also often related toabnormal pigmentation. Textural and pigmentarychanges are more marked than in level 1. Thesepatients may have actinic keratosis, liver spots(senile lentigines or flat seborrheic keratosis), and adefinite increase in wrinkling. The increased wrink-ling is usually seen in the infraorbital areas andlateral to the nasolabial groove, where the skin mayappear atrophic and crinkled.
Level 3 Clinical signs are due to alterations in the
epidermis, papillary dermis, and reticular dermis. Themost severe form of photodamage, level 3 is associatedwith many of the clinical changes seen in levels 1 and2. These patients, however, also have marked wrinklingusually associated with a thickened leathery appear-
ance and feel and also a yellowish tint of the skin. Inaddition, the skin of some patients has a pebbly textureand scattered open comedones.

On the basis of this classification of photodamaged skin,the peel must be as deep as the deepest skin problem toachieve the best results. Chemical peels create a thinner,more compact stratum corneum, associated with a thicker,acanthotic epidermis without atypia and with a uniformdispersion of melanin. Ephelides, epidermal melasma, andepidermal hyperpigmentation respond excellently to epider-mal peels, whereas senile lentigines and lentigines simplexdo better with papillary dermal peels. Nevi, dermal andmixed melasma, dermal and mixed postinflammatoryhyperpigmentation, and seborrheic keratoses respond poorlyto superficial and medium-depth chemical peels.

Because peels have the ability to create a thickerepidermis, more collagen and glycosaminoglycans in thepapillary and reticular dermis, and more elastic stainingfibers in the dermis, they bring about an increased volume oftissue, which tightens the superficial skin layers, leading toan improvement of wrinkles. Deeper peels result in a greaterdeposition of collagen and glycosaminoglycans. Therefore,lighter peels help the more superficial types of wrinkles,whereas deeper peels are needed to improve deep lines.

The overall results of chemical peels depend mostly onthe histologic depth of the lesions. For instance, if a patienthas dyschromia located in the epidermis and fine wrinklingdue to papillary dermal atrophy and damage, a peel is neededthat corrects papillary damage to obtain the best resultsbecause an epidermal peel will improve only the dyschro-mias with little or no effect on wrinkling.

Techniques of application of chemical peels

Patient selection

The success of a chemical peel depends on a carefulselection of patients and individualization of the treatment.Skin texture, thickness, degree of photoaging, severity offacial rhytids, and age-related gravitational changes must allbe considered.

Extent of skin damageAs a rule, patients with mild facial rhytids and/or minimal

dyschromias are the best candidates for superficial tomedium-depth chemical peels. Deep rhytids and excessivefacial skin are likely to respond best to traditionalrhytidectomy. Some patients may benefit from bothprocedures because excess skin is removed by rhytidectomy,whereas the quality of the skin is addressed by the chemicalpeel. A minimum of 3 months is recommended between the2 procedures to allow for complete wound healing, however.Patients' expectations should be discussed so that the extent


to which the facial lesions and/or photoaging will beenhanced by the procedures is understood.1

ComplexionEvaluation of skin type and complexion is very

important to determine which chemical peels would besuitable for the patient and which patients are at greater riskof pigmentation abnormalities complicating the peels. TheFitzpatrick classification of skin types (I-VI) is often used.It refers to the ability of skin to acquire a tan or burn afterUV light exposure.15

Skin types I to III do not usually develop postinflamma-tory hyperpigmentation, and patients with these skin typesare therefore excellent candidates for undergoing chemicalpeels. Patients with skin types IV to VI have a much higherrisk of hypo- or hyperpigmentation complications.1

Patient's lifestyle7

The patient's lifestyle should always be considered.Compliance with pre- and postpeel treatment must beassured. The patient must be motivated enough to stick toa daily regimen for a few weeks before and after theprocedure. The patient must also be able to put up with theerythema and scaling that occur after a peel. Early sunexposure has to be avoided after a peel, and outdooroccupations may therefore make a patient unsuitable forchemical peeling.

Sex7

Men often have thicker and oilier skins as compared withwomen. This might cause uneven penetration of the peelingagent. Also, men are less likely to use camouflage makeup ifpigmentary complications arise. These factors might makemen less optimal candidates for chemical peels.

Medical history7,16

A thorough medical and drug history is very important.Medical conditions such as cardiac, hepatic, or renal diseasemay influence treatment decisions and the choice of peelingagents. Exogenous estrogens, oral contraceptives, and othermedications may be photosensitizing and predispose patientsto pigmentation complications after chemical peeling.

Prior treatments such as radiation or oral isotretinoinreduce the number of epithelial appendages, causing re-epithelialization to occur more slowly, increasing the risk ofscarring after a chemical peel. It is advisable that at least 12months must elapse after treatment with isotretinoin beforeproceeding with a chemical peel. This will ensure someregeneration of epithelial appendages and reduce the riskof complications.

A history of herpes simplex requires antiviral prophylaxisfrom the immediate prepeel period until re-epithelializationis complete. Some dermatologists advise prophylaxis in allpatients to avoid the risks of a herpetic outbreak. Anyexisting lesion must heal completely before undergoing achemical peel.

Therefore, although the technique of chemical peelingmight be relatively simple, great care must be taken forproper patient and peeling agent selection to minimize therisks of complications.

Preprocedure care

Preconditioning or priming of the skin is very importantto improve peel results and reduce the risk of complications.The more the pigment and the darker the complexion thelonger, the preconditioning treatment should be continuedbefore a chemical peel. A minimum period of 2 weeks isimportant to sufficiently prime a patient.

Fulton and Porum17 suggest a step-by-step skin rejuvena-tion program. It is suggested that minor photoaging isreversed first with avoidance of free-radical generators, suchas cigarette smoke and UV light exposure. A daily skin careregimen is then used, which produces a slight skin peelingonce a week. Avoidance of unprotected sun exposure for atleast 2 months before and after treatment is advised, and abroad-spectrum sunscreen must be used.

α-Hydroxy acids18-20

α-Hydroxy acids (AHAs) are a group of organic acidsderived from fruits and therefore often referred to as fruitacids. They include glycolic acid from sugar cane, citricacid from citrus fruits, and malic acid from apples, and arenow manufactured in laboratories. α-Hydroxy acids causea superficial exfoliation by keratinocyte dyscohesion(ungluing) of pathologically sticky cells at the level ofthe stratum granulosum in the epidermis. This allows thepathologic cells to become loose and shed and thereforehelps to correct an abnormally thickened stratum corneum.This effect lasts for up to 14 days after cessation oftherapy. Also, the daily use of AHAs increases theepidermal thickness. In the dermis, there is an increasein the deposition of collagen and glycosaminoglycans,resulting in increased dermal thickness. α-Hydroxy acidsare especially good for priming patients who have a verysensitive skin, a ruddy complexion, telangiectasias, orsevere sun exposure.

Retinoic acid21,22

Retinoic acid is commonly used either alone or incombination with AHAs or other ingredients. It causesthinning and compaction of the stratum corneum andthickening of the epidermis. It also improves dyschromiasby dispersing melanin throughout the epidermis and reverseskeratinocyte atypia, thus improving or eradicating actinickeratosis. In the dermis, there is stimulation of collagendeposition and capillary arborization. These effects result inan improved skin texture; improvement of superficialdyschromias; and a pinker, rosier hue of the skin. Photo-sensitivity is, however, associated with this product, andpatients must avoid excessive sunlight during its use.


Because AHAs and retinoic acid have different modes ofaction, with retinoic acid acting mainly on the stratumcorneum, whereas AHAs act mainly on the stratumgranulosum, they are often used in combination, especiallyin patients with thick, oily skin.

Reducing wound healing timeThe use of retinoic acid and AHAs accelerates the skin

turnover from the normal 28 days to 10 to 12 days. Facialre-epithelialization after a 35% TCA is speeded up by about24 hours. They are usually used for at least 4 weeks beforethe procedure.

Achieving uniform penetration of the peeling agent23

The stratum corneum, which provides a protective barrieron the skin, varies in thickness over different areas of the face.Therefore, its ability to block the penetration of a peelingagent also varies in different areas. Thinning the stratumcorneum facilitates a uniform penetration of the peeling agent.This is achieved with the use of AHAs and retinoic acid.

Decreasing the risk of postinflammatoryhyperpigmentation23

Chemical peels may induce postinflammatory hyperpig-mentation. Because retinoic acid and glycolic acid enhance thedispersion ofmelanin granules through the epidermis, they havea skin-lightening effect and are therefore helpful in reducing theincidence of postinflammatory hyperpigmentation.

Other bleaching agents such as hydroquinone, and kojicacid, inhibit tyrosinase. This blocks the conversion oftyrosine to L-dopa and may decrease skin's ability to producemelanin, therefore decreasing the risk of hyperpigmentation.They are usually started about 2 weeks before the peel andcontinued for 2 or 3 months after the peel. Azelaic acid isalso used as a bleaching agent, but it is less effective andmore irritating to many patients.

The use of bleaching agents is especially important inpatients undergoing peels to improve hyperpigmentation andin those who have a great risk of developing postinflamma-tory hyperpigmentation.

Preparation for postpeel maintenance regimen23

Maintenance therapy after a peel is important to achieveand maintain best results. This usually involves the use ofretinoic acid, bleaching agents, and sunscreens. It isimportant that the patient is started on the products to beused after the peel before the procedure is performed, so thatany temporary sensitivity reaction of the products in theimmediate postpeel days, occurring because the skin is moresensitive during this time, may be differentiated from aspecific allergic reaction to the product.

Skin cleansingThe patient should thoroughly cleanse the face with

nonresidue soap the day before the peel and should notapplymakeup ormoisturizers. Immediately before starting the

procedure, the skin is cleansed to remove any remaining tracesof makeup or oils, using ether, acetone, or isopropyl alcohol.Cleansing the skin before a chemical peel is of utmostimportance to prevent uneven penetration of the peeling agent.

Postoperative care

The healing process after a chemical peel must be as rapidas possible so as to avoid infections with bacteria, includingPseudomonas, yeasts such as Candida, or viruses such asherpes. Infectionsmay deepen thewounds, extending the peelfrom superficial to a deep peel, with the concomitant risks ofscaring. Deep peels may be prophylactically treated withantimicrobials, but more superficial peels are simply keptmoist with the application of petrolatum-based products.After re-epithelialization, and when skin appearance is backto normal, a regime of AHAs, retinoic acid, bleaching creams,moisturizers, and sunscreens should be restarted. Sunexposure must be avoided for 6 weeks after the peel tominimize the risks of postinflammatory hyperpigmentation.

Classification of peeling agents24

Peeling agents are classified according to the depth of peelthey cause. Many variables can alter the depth of peeling achemical agent can cause, including the following:

1. The nature and concentration of the peeling agent;2. The number of coats applied/length of time the agent is

in contact with the skin;
3. Technique of application (painted or rubbed in);4. Priming of the skin in the weeks preceding the peel;5. Cleansing and degreasing the skin before the peel;6. Type of patient's skin; and7. Anatomical location of the peel.
It is therefore very important to standardize peelingprocedures by treating all patients in a similar manner, usingsame skin priming and cleansing procedures before peelingand similar techniques of application of the peeling agent.

Peeling agents can be classified as follows.Very superficial agents include the following:

• Glycolic acid, 30% to 50%, applied briefly (1 to 2
minutes);
• Jessner solution, applied in 1 to 3 coats;• Low-concentration resorcinol, 20% to 30%, applied
briefly (5 to 10 minutes); and
• TCA 10%, applied in 1 coat.

Superficial agents include the following:

• glycolic acid, 50% to 70%, applied for a variable time
(2 to 20 minutes);
• Jessner solution, applied in 4 to 10 coats;


• Resorcinol, 40% to 50%, applied for 30 to 60 minutes;
and
• TCA, 10% to 30%.

Medium-depth agents include the following:

• Glycolic acid 70%, applied for a variable time (3 to
30 minutes);
• TCA, 35% to 50%; and• Augmented TCA (carbon dioxide plus TCA 35%;
Jessner solution plus TCA 35%; glycolic acid 70% plusTCA 35%).
Deep agents include the following:

• Phenol 88% and• Baker-Gordon phenol formula.

Specific chemical peels

Jessner peels25

Jessner solution is used for light peels alone or inpreparation for a TCA peel. The preparation is made fromsalicylic acid, 14 g; resorcinol, 14 g; lactic acid (85%), 14 g;and ethanol to 100 mL. Its shelf life is 2 years if the containeris opened only for 5 minutes every month, and it darkenswith age and exposure to light and air.

The solution is applied to the skin with a soft applicatorin patients with thin sensitive skin or rubbed in with gauzesquares in patients with thick sebaceous skin. The depth ofthe 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-lookingwhitening of the skin surface. This is not frosting(coagulation) but probably simply the precipitation ofchemicals on the skin and can be easily wiped off. Thislevel of peel (level 1) created with 1 to 3 coats of Jessnersolution is very superficial and only causes mild flaking ofthe skin for 1 or 2 days or none at all.

A level 2 peel is created with the application of more(4-10) coats of the solution. There is increased erythema andsome pinpoints of true white frosting. There is mild tomoderate burning and stinging, which lasts for 15 to 30minutes. In the next 1 to 3 days, a mild red-browndiscoloration develops, and the skin feels tight. Exfoliationthen follows for 2 to 4 days, with moderate flaking but rarelyactual peeling.

Further coats of Jessner solution create a level 3 peel,where there is prominent erythema and increased areas offrosting associated with a moderate amount of stinging. Atthis level, exfoliation usually lasts 8 to 10 days, and theremight be actual peeling apart from the dry flaking of the skin.Crusting and weeping does not occur, however, because it isstill an intraepidermal peel.

Different patients may require different number of coats toachieve the same level of peel. This is because penetration ofthe solution depends on a number of factors, including thepreparation of the skin, the thickness of the corneum, and thesensitivity of the skin. Four to 6 minutes should be allowedafter application of a coat of the solution to evaluate the fullskin reaction to the solution.

During the healing phase, it is important for the patient touse a bland moisturizer to relieve the tight, masklike feel ofthe skin. A mild topical steroid may be applied if there ispersistent stinging or sensitivity. Makeup may be used in thehealing phase, but scrubs, masks, astringents, toners, orretinoic acid and AHAs may only be applied after 48 hoursafter the peel has healed.

The advantages of Jessner solution are that the peel is verysuperficial and safe and rarely goes deeper than one wouldexpect. A fairly uniform peel is created, and there is asignificant amount of exfoliation, which is ideal for treatingdyschromias. Concentration of resorcinol is low, and there-fore, there is a very low risk of resorcinol toxicity.Disadvantages include erythema and discoloration, whichare associated with this peel and which may be quite difficultto cover up with makeup.

Complications, including allergic reactions, are very rare.Toxicity to salicylic acid only occurs if the area being treatedis very large, such as when treating the face, chest, arms, andlower legs simultaneously. Infections are very rare becausethe peel is only intraepidermal. Erythema may complicateJessner peels, but it is always self-limiting. This can betreated with a mild topical steroid and emollients.

Glycolic acid peels26

Glycolic acid is the most commonly used AHA as apeeling agent. Its natural source is sugar cane, but it ismanufactured in the laboratory for use as a chemical peel. Itcan be used as a daily skin care product in low concentrationsof 5% to 15%. Greater concentrations of 30% to 70% areused for chemical peels. The higher the concentration, thedeeper the peel they produce. α-Hydroxy acid peels are usedcommonly for several reasons. They are systemically safeand nontoxic and produce superficial peels capable ofsignificant effects but with few complications. They are alsowell tolerated by patients.

All AHA peels need to be neutralized to terminate theiraction on the skin when the desired depth of wounding hasbeen achieved. Neutralization is best affected by applying analkaline solution such as sodium bicarbonate, which causes alot of fizzing on the face. Other neutralizing agents do notcause such fizzing. Washing the face with water is also goodbut may not remove all the glycolic acid.

Therefore, the depth of a glycolic acid peel depends onthe strength of the glycolic acid and the length of time thisis left on the skin neutralized. Seventy percent freeglycolic acid left on the skin for 15 minutes causes a


dermal wound as deep as 40% TCA. For this reason, it issafer to start with 50% glycolic acid, which can be left onthe skin longer. Preparations of glycolic acid that have alower pH create more burning, stinging, irritation, anderythema and are therefore less tolerated by patients thanpreparations with a higher pH. Also, preparations with alower pH may penetrate the skin more unevenly, causingareas of accidental deeper peeling. The depth of the peelmay also be affected by the sensitivity of the skin,excessive priming of the skin, and any recent wounding ofthe skin.

When applying a glycolic acid peel, a few precautionsshould be taken. Firstly, the neutralizing agent must beready at hand. Application of the acid to the whole faceshould be done rapidly so that different parts of the facewould not be exposed to the acid for different periods. It isalso advisable to start the peel from the forehead becausethis area can tolerate a slightly longer period in contactwith the acid.

Once the whole face has been treated, one should watchout for areas of erythema or epidermolysis because thesemust be neutralized immediately. Some areas of the face mayabsorb the acid faster. These include areas such as the alargroove, nasolabial fold, lateral canthus, oral commissures,and just inferior to them on the chin. Reasons for thisincreased sensitivity are a thinner stratum corneum orunderlying xerosis. It is therefore advisable to protect thesevulnerable areas with a thin smear of petrolatum before thechemical peel application.

A fan may be used during the procedure to alleviate themild stinging or burning discomfort associated with thisprocedure. As time passes, the depth of the glycolic acid peelincreases, and this can be seen clinically as the skin becomespink first, changing to red, signifying intraepidermalwounding. Gray-white coloring and vesiculation occurwith epidermolysis or separation of the epidermis from thedermis and hydration. Frosting signifies dermal injury.

The depth of the peel performed depends on what lesionsare being treated. Therefore, only superficial epidermalnecrosis may be required to treat some patches ofhyperpigmentation, although one must be careful becauseit might make postinflammatory hyperpigmentation worse.For significant improvement of wrinkling, one needs tocreate epidermal necrosis and dermal inflammation. Healingtakes around 5 to 7 days, and there is crusting during thistime. The deeper the peel, however, the larger is the riskof complications.

For postpeel care, a bland emollient applied oftenduring the day is all that it is usually needed. Thenormal maintenance regimen of AHAs should be startedagain when skin sensitivity and appearance are back tonormal. Glycolic acid peels may be repeated as often asthere is evidence of additional improvement with eachpeel. A few weeks must elapse before repeating the peelto allow for resolution of any dermal inflammation thatmay have occurred.

Glycolic acid peels can be applied to other sun-damagedareas including the neck, chest, and dorsum of the hands.There is an improvement of mottled hyperpigmentation andfine wrinkling, but significant wrinkling and dark pigmenta-tion are usually resistant to the treatment. Peels should besuperficial in nonfacial areas to avoid scarring.

Trichloroacetic acid peels1,27,28

Trichloroacetic acid can be used to create superficial,medium, or deep peels. Apart from variables such aspatient's skin type, adequacy of skin priming, layers ofacid applied, and technique of application, the mostimportant factor affecting the depth of the peel is theconcentration of TCA used. Concentrations of 10% to 25%are used for intraepidermal peels, whereas 30% to 40% areused for papillary dermal peeling. It is most commonly usedfor medium-depth peels, especially to treat pigmentationdisorders and early facial rhytids.

The skin is prepared and cleansed as for other peels.Trichloroacetic acid is applied using cotton tipped applica-tors or gauze sponges, with the patient best seated with thehead elevated at 45° for comfort and to avoid pooling of acid.Special attention should be paid around wrinkles, so that theacid gets to the bottom of the wrinkles. Overlap of coatsshould be avoided to prevent deep wounding. The peelshould be carried through the eyebrows and also a littlebeyond the hairline and below the jawline.

The depth of the peel can be judged from the appearanceof the skin. Trichloroacetic acid is a chemical cauterant thatcoagulates proteins in the skin. A very light applicationproduces minimal erythema, and this corresponds to a verysuperficial peel removing mostly the stratum corneum. Asuperficial epidermal peel is created when the skin showssome erythema with irregular patches of light frosting. Thisshould heal after 2 to 4 days of light flaking. Uniform whitefrost on a background of erythema signifies a full-thicknessepidermal peel that heals after about 5 days. When noerythema shows through a solid white frost, it is assumed thatthe peel has extended to the papillary dermis, and this takesup to 7 days to heal.

A cream or ointment with 1% hydrocortisone may beapplied immediately after the procedure to soothe the skin.During the healing phase, great care should be taken of theskin. In the healing phase, sun exposure must be avoided.Heavy exercise and sweating must also be avoided, and theface should not be unnecessarily touched. Peeling usuallystarts after about 2 days around the perioral region andcontinues from the central face outward, making the faceunsightly for 4 to 6 days. It is important to keep the skinmoist with the use of bland emollient creams or ointmentsduring this time to avoid premature peeling.

Trichloroacetic acid can also be used for nonfacial peels,but care must be taken so as not to perform dermal peelsbecause of the risk of scarring. It may therefore be advisableto use lower TCA concentrations for nonfacial peels.


Combination peels

Combination peels are used to enhance the penetration of alow-concentration TCA, or other acids, thus minimizing therisks of scarringwhile the acid still penetrates as deeply as 50%TCA. The most commonly used combinations are as follows.

Jessner solution and TCA (Monheit peel)29

This peel combination was popularized by Cary Monheit.After priming the skin as for other peels, 1 to 4 layers ofJessner solution are applied until there is generalizederythema with areas of light frost. Thirty-five percent TCAis then applied, which penetrates more rapidly, uniformly,and deeply than if it were applied on its own, especially if thepatient's skin is thick and sebaceous. These peels can berepeated every 3 to 4 months to maintain an improvement ofthe fine lines of aging.

Solid carbon dioxide and TCAThis combination, which has been studied by Dr Hal

Brody, is used to peel different areas of the skin to differentextents. After priming the skin as for other peels, areas thatneed deeper peeling, such as wrinkles or rims of scars, are firsttreated with solid carbon dioxide dipped in a solution ofacetone and alcohol to help it glide over the skin. The longerthe time and the greater the pressure exertedwhen applying thesolid carbon dioxide, the deeper the peel. When the burning ortingling sensation from the carbon dioxide has subsided, 35%(or other concentrations) TCA is applied to the whole face.

Glycolic acid and TCA30

After normal priming of the skin, 70% glycolic acid isapplied to the skin for 2 minutes without prior cleaning of theskin. Trichloroacetic acid 35% is then applied. Thiscombination is thought to result in a more uniform anddeeper peel than TCA used alone.

Jessner solution and glycolic acid31

This technique was studied by Dr Larry Moy. It involvespriming the skin and then applying 1 to 3 coats of Jessnersolution, causing the skin to become diffusely erythematous.The skin is then treated with 70% glycolic acid. Thisprocedure again produces a more uniform glycolic acid peel.Also, exfoliation from the use of Jessner solution is combinedwith the stimulatory effects of glycolic acid. It is also a riskyprocedure because the skin is already red from the applicationof Jessner solution, and it is easy to then overpeel the patient.

Complications1,16

Tears

Tears coming down the cheek can dilute the acid appliedon the cheek and drip onto the neck, causing a peel in an area

that is more prone to scaring. It is therefore very important todab off any tears and immediately wash those that fall. Theneck may be protected with a layer of petrolatum.

Premature peeling

Premature peeling predisposes the underlying skin to risksof infection, persistent erythema, postinflammatory hyper-pigmentation, and scarring. It may occur accidentally or maybe the result of picking at the peeling skin. If non–re-epithelialized tissue (moist looking) is exposed, patientsshould be started on regimens of oral antibiotics until re-epithelialization occurs. Aggressive wound care managementmay include the use of topical antibiotics and hydrocolloiddressings. Topical steroid ointment or cream is used ifepithelialized bright red skin is exposed on premature peeling.

Infection

Infections occur more commonly with deep peels anddeepen the peels, thus increasing the risk of scarring.Common bacterial pathogens include staphylococci andstreptococci. Pseudomonas and nitrobacteria infections alsooccur. Infections are treated with topical and oral antibiotics.Topical ointments are applied frequently to help keep thewound moist and enhance healing.

Herpetic outbreaks may occur, usually starting on the lipor above the vermilion border. They usually present aspainful erosions, and outbreaks are prevented with the use ofprophylactic oral acyclovir. Thrush may also occur along thelips and oral mucosa and may be treated with oralitraconazole or fluconazole.

Acneform eruptions

These may occur during or just after the peeling phase andpresent as multiple tender erythematous follicular papules.They respond to the oral antibiotics used in the treatment ofacne such as tetracycline, minocycline, or erythromycin.

Postinflammatory hyperpigmentation

Postinflammatory hyperpigmentation occurs more fre-quently in patients with dark complexion. It may developvery soon after the peel or months later, and it is often theresult of early sun exposure after the peel. Sun avoidance andthe daily use of sunscreen are very important for itstreatment. Oral contraceptives may exacerbate hyperpig-mentation, and if possible, they should not be used during theperipeel period. Epidermal postinflammatory hyperpigmen-tation responds well to various treatments, whereas dermalhyperpigmentation, not so well. Bleaching agents such ashydroquinone and kojic acid may be used to graduallylighten the pigmentation, especially in combination withretinoic acid or AHAs, which cause the shedding of the


epidermis. Light peels that do not create inflammation, suchas 10% TCA, Jessner solution, or 50% to 70% glycolic acidmay be used to treat postinflammatory hyperpigmentation.

Hypopigmentation

Peels that cause exfoliation lighten the skin because of theshedding of cells containing melanin. In deep peels wherethe entire epidermis is removed, new melanocytes migrateto the epidermis from the hair follicles, and this takes 2 to3 months. With reticular peels, some areas of permanenthypopigmentation frequently result because of the destructionof melanocytes in the hair follicles. Most patients with thisproblem require cosmetics to camouflage the affected areas.

Persistent erythema

Although erythema is common and quite normal after anypeel, patches of erythema persisting for more than 3 weeksmay be a sign of developing hypertrophic scars and are besttreated with a class 1 potent topical corticosteroid. Pulseddye laser may also be used, but it is more expensive andleaves unsightly purpura lasting up to 3 weeks.

Scarring

Although uncommon, there is an increased risk ofscarring in certain patients. These include those with aknown history of poor healing and keloid formation, patientsundergoing deep peels or a second peel very soon after aprevious peel or surgery without waiting for adequately skinhealing, patients who have been previously treated withisotretinoin especially in the previous year, and patients whodevelop an infection during the peel. Scarring may takedifferent forms. It may develop as hypopigmented, flat,shiny, sheetlike areas. There may also be atrophic scars,hypertrophic scars, or keloid formation. Hypertrophic scarsoccur most commonly along the mandibular border and inthe perioral region. Most scars are secondary to othercomplications such as infection or premature peeling, andtherefore, a careful monitoring of the patient in the postpeelphase is very important for early detection and treatment ofsuch complications. At least 1 year should have elapsed afterthe use of isotretinoin before any peel is attempted.

Hypertrophic scars and keloids are best treated withpotent corticosteroids topically or intralesionally. Closefollow-up is necessary. Resistant scars may be treated withdermabrasion or pulsed dye laser followed by compressivesilicone sheeting therapy.

Conclusions

The largely predictable outcome and the favorable risk-benefit ratio of superficial to medium-depth chemical

peels in experienced hands still render this resurfacingmodality an attractive option, although considerable timehas passed since the first peels appeared on the marketand in spite of the development of more modernrejuvenating techniques. It is, however, recommended tocombine chemical peels with other rejuvenating techni-ques to achieve the best end result and patient satisfaction.The deep peels are somewhat less popular nowadaysbecause of the associated prolonged downtime andincreased risk of complications.

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superficial and medium-depth chemical peels

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