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Keywords:

  • chemical peels;
  • glycolic acid;
  • lipo-hydroxy acid;
  • phenol;
  • photoaging;
  • trichloroacetic acid

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

Background/Objectives  Peelings are among the oldest and most widespread aesthetic procedures used in aesthetic dermatology worldwide. More than 50 commercial peelings are currently available on the European market.

Materials and Methods  In the present review, we summarise the current knowledge on chemical peels.

Results/Conclusions  A state-of-the-art peeling procedure will take into account the depth of the targeted structure and the skin condition of the patient to choose carefully among the variables such as chemical class of the peeling agent, concentration, frequency and pressure of the application. The usual classification of chemical peels comprises superficial, medium and deep peels. For superficial peels alpha-hydroxy-acids and most recently lipo-hydroxy acid are used to induce an exfoliation of the epidermis. Medium-depth agents such as trichloroacetic acid (< 50%) cause an epidermal to papillary dermal peel and regeneration. Deep peels using trichloroacetic acid (> 50%) or phenol based formulations reach the reticular dermis to induce dermal regeneration. The success of any peel is crucially dependent on the physicians understanding of the chemical and biological processes, as well as of indications, clinical effectiveness and side effects of the procedures.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

Chemical peels are methods to cause a chemical ablation of defined skin layers to induce an even and tight skin as a result of the regeneration process. The actual peeling procedure involves the application of a caustic chemical substance to destroy layers of the skin such that they are then spontaneously eliminated over several days and repair mechanisms of the epidermis and dermis are induced. The mechanical action of peeling, even when limited to the epidermis, is able to stimulate regeneration via pathways in the dermis that are not well understood. The depth of destruction depends on the substance used and its concentration. The use of chemical peels has been reported since antiquity, but a standardized and scientifically based technique has emerged only over the past decades.

History

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

The earliest use of caustic preparations for peeling procedures was described in the Egyptian medicine in the Ebers papyrus as early as 1550 BC.1,2 Reports are also found in the ancient Greek and Roman literature. Over the past centuries, some formulas have apparently been transmitted by gypsy populations. Dermatologists began to show interest in peeling in the 19th century. In 1874 in Vienna, the dermatologist Ferdinand von Hebra used the technique to treat melasma, Addison’s disease and freckles. In 1882 in Hamburg, Paul G. Unna described the actions of salicylic acid, resorcinol, trichloroacetic acid (TCA) and phenol on the skin. Their initial work was followed by that of many other authors.1

The use of phenol was developed after World War I in France.3 In England, MacKee had already worked with phenol for the treatment of scars, but he did not publish his results until 1952.4 Meanwhile, in the United States during the 1940s, Eller and Wolff provided the first systematic description on the use of phenol, resorcine, salicylic acid and CO2 for the treatment of scars.5 The modern era of peeling began in the 1960s with the development of modified phenol solutions (addition of croton oil, septisol and water) by Baker and Gordon6 and histological assessment of peeling results by comparing phenol and TCA peels.7 The scientific basis for TCA peels was extended in the 1970s and early 1980s by the comparison of the histological effects of three TCA concentrations.8 In parallel, at that time, alfa-hydroxy acids (AHA) were developed by van Scott and Yu as more superficial peels for hyperkeratosis.9 Subsequently, peeling with glycolic acid, the most commonly used AHA, was developed.10 The description of combinations of two superficial peeling substances (Jessner’s solution and TCA 35%) by Brody and Haily11 and later by Monheit12to achieve medium-depth effects provided further progress in the development of chemical peels. The latest development is the use of lipo-hydroxy acid (LHA).13

Classification

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

Chemical peels are classified into three categories based on the depth of destruction caused by the treatment14:

  •  Superficial peels, which exfoliate epidermal layers without going beyond the basal layer.
  •  Medium-depth peels, which reach the upper layers of the dermis down to the papillary dermis.
  •  Deep peels, which remove the papillary dermis and reach the reticular dermis.

Some authors discriminate between very superficial (exfoliation) and superficial (epidermal) peels. The depth of peeling depends on several factors – the substance used, its concentration, the pH of the solution and the time of application. For example, TCA is used for superficial, medium-depth or deep peels, depending on its concentration. Furthermore, combinations of substances that each act as superficial peels may add up to synergistic effect of a medium-depth peel (e.g. Jessner’s solution and TCA 35%).

General principles of peeling procedures

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

The process and the technique of a peeling procedure are largely determined by the chemical’s nature and the concentration of the applied peeling substance. However, most peeling procedures follow a typical sequence of steps.

Pre-peeling preparation (priming)

Because of the relevance to the final treatment result and the rate of complications, the importance of a consistent pre-treatment phase cannot be underestimated.13 Therefore, any doubt regarding the reliability of the patient should disqualify for a peeling procedure.

The purpose of the pre-treatment phase is to prepare the skin for the peeling process and for the following regeneration phase. To achieve this, tretinoin is usually applied for one month beforehand because its action on the skin facilitates a more homogeneous penetration of the peel, leading to a more consistent result. Moreover, preparation with tretinoin also facilitates to accelerate the post-procedural healing process.13–15 The concentration of tretinoin used depends on skin tolerance. In case of intolerance, tretinoin can be replaced by an AHA. To prevent post-inflammatory hyperpigmentation, the epidermal melanogenesis needs to be inactivated13,14 by the daily use of sunscreens. In patients with a dark phototype, an additional treatment with a hydroquinone-based preparation may be required.

In patients with a history of herpes infection, medium-depth or deep peels are preceded with oral anti-herpes treatment started the day before the procedure and continued for 1 week after.13,14 This prevents the majority of herpes outbreaks during post-peeling healing (Table 3).

Table 3.   Clinical effect after four treatments
Treatment stepsPeeling agentPeeling level
SuperficialMedium–deepDeep
AHA (glycolic acid, pyruvic acid) BHA (salicylic acid, LHA)TCA 35% or combinationsTCA >50% phenol
  1. TCA, trichloroacetic acid; AHA, alfa-hydroxy acids; BHA, beta-hydroxy acids; LHA, lipo-hydroxy acid.

Preparation (Priming)Time1–2 weeks prior to first session2–3 weeks prior to session
PurposeTo prepare the skin by starting the exfoliating process To optimize and homogenize the penetration of the peel solutionTo prepare the skin by starting the exfoliating process To regulate pigment content in patients with strong pigmentation
SolutionsLHA Cleansing gel LHA solution (0.25% LHA) LHA Serum (0.45% LHA)Topical AHA or BHA Topical retinoids Vitamin C Vitamin ECreams and solutions containing:  Topical retinoids  Vitamin C/vitamin E  Depigmenting solution (e.g. hydroquinone 1.0/dexamethasone 0.02/tretinoin 0.0125/Ung. emulsif. nonion. ad 20.0)
ProceduresDaily cleansing Gel and/or solution daily skin care LHA Serum, 0.45% LHADaily application over 3 weeksDaily application over 3 weeksDaily application over 3 weeks
 PurposeCleaning and degreasing of skin prior to treatment to achieve homogenous peeling results No sedation or analgosedationCleaning and degreasing of skin prior to treatment to achieve homogeneous peeling results SedationCleaning and degreasing of skin prior to treatment to achieve homogeneous peeling results Analgosedation
SolutionsLHA Solution (0.25%) degreasing wipe (vaseline) Hexachlorophene cleanser Acetone or acetone–alcohol mixture Gauze pads Diazepam 5–10 mg p.o. Hexachlorophene cleanser Acetone or acetone–alcohol mixture Gauze pads Diazepam 5–10 mg p.o. ± Non-steroidal antiphlogisticsHexachlorophene cleanser Acetone or acetone–alcohol mixture Gauze pads Diazepam 5 mg + pentazocin 15 mg i.v. + Regional block (bupivacaine) + Non-steroidal antiphlogistics 1.0–1.5 l volume infusion
ProcedureEye protection (patient and physician) Cleansing (no rinsing) Degreasing with wipe (vaseline protection for sensitive areas) Eye protection (patient and physician) Cleansing with hexachlorophene Thorough rinsing with water, dry Degreasing with acetone or acetone–alcohol mixture (vaseline protection for sensitive areas) Eye protection (patient and physician) Cleansing with hexachlorophene Thorough rinsing with water, dry Degreasing with acetone or acetone–alcohol mixture (vaseline protection for sensitive areas) Eye protection (patient and physician) Cleansing with hexachlorophene Thorough rinsing with water, dry Degreasing with acetone or acetone–alcohol mixture (vaseline protection for sensitive areas) ECG control required
TreatmentTime++++++++++
PurposeExfoliation of epidermal layerActual peeling processActual peeling process
SolutionsCotton-tip applicators LHA solution (5%, 10%)Brush or gauze AHA (e.g. glycolic acid 20%)Cotton-tip or gauze TCA alone (e.g. 35–50%) TCA combination (e.g. Jessner’s solution + TCA 35%)Cotton-tip or gauze, (waterproof tape) Phenol solution (e.g. Baker–Gordon solution: phenol 50%, 2% croton oil) TCA combination (e.g. Jessner’s solution + TCA 35%)
ProcedureApplication to facial units in order of fig. 2. 1–3 layers, depending on skin typeApplication to facial units Variable number of layersAppliction to facial regions Combinations:  1. Jessner’s solution  2. TCA solution (variable number of layers) Applcation to each facial region with 5–15 min intervals between regions One application per region (occlusion with waterproof tape)
NeutralizationNoYesYesYes
Frequency4(4)-6-(8)11
Post-treatmentTime15 days 15–28 days1–2 months2 months
PurposeTo stabilize and enhance the exfoliating process To prepare skin for next peeling procedureTo prevent infection and pigmentation disorders To enhance the regeneration processTo prevent infection and enhance wound healing prevent pigmentation disorders
SolutionsLHA cleansing gel LHA solution (0.25% LHA) LHA serum (0.45% LHA)Topical AHA or BHA in Topical retinoids Vitamin C/vitamin EBland emollient cream NaCl solution or acetic acid soaked compresses alternatively Non-steroidal anti-inflammatory drugs (e.g. acetyl salicylic acid) Bland emollient cream Antibiotic skin cream (e.g. refobacine) 0.25% Acetic acid Non-steroidal anti-inflammatory drugs (e.g. acetyl salicylic acid)
ProcedureDaily cleansing with gel and/or solution, no rinsing Daily skin care, LHA serum 0.45% LHADaily application over 3 weeks Thorough rinsing requiredSoak face 4–5 times in first 24 h Apply bland emollient cream and wet NaCl or acetic acid soaked compresses alternativelyLeave occlusion for 12–48 h Debridement by soaking with acetic acid solutions and compresses Open and/or occlusive application of emollient and/or antibiotic creams
General remarksDaily application of a sunscreen product with an SPF 15 or higher with UVA/UVB for 2–3 months usually no antiviral treatment requiredDaily application of a sunscreen product with an SPF 15 or higher with UVA/UVB for 6 months Optional antiviral treatment (e.g. acyclovir 400 mg 2×/d) Daily application of a sunscreen product with an SPF 15 or higher with UVA/UVB for 6–12 months Antiviral pre- and post-treatment required (e.g. acyclovir 400 mg 2×/day)

Pre-treatment

A pre-treatment cleansing step directly prior to the actual application of the chemical peel substance is a consistent part of every peeling protocol. It is crucial to obtain a homogeneous penetration of the peel and thus a uniform result.14 The application technique is very simple. The skin is first systematically and thoroughly cleansed to remove fats and oils and to eliminate debris from the stratum corneum – some authors use acetone for this.14 The skin is then rinsed and dried (Table 3).

Treatment

The peeling agent is then applied using, for example, compresses, cotton, an applicator or a brush. Contact time depends on the caustic agent used and the desired depth. The peel is neutralized with sodium bicarbonate or water, as necessary.

Each session is terminated with the application of a hydrating and healing cream. Some authors place bandages after treatment with medium-depth and deep peels.13 Treatment can involve the entire face or only a part. In the latter case, facial anatomy is divided into four aesthetic units (upper lip, both cheeks and forehead; fig. 1).16,17 Each unit is treated in its entirety to avoid an excessively visible demarcation line between treated and untreated zones.15

image

Figure 1.  Facial treatment areas for the peeling procedure.

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Patients should be advised that the treatment may be painful:

  •  Usually, just a simple sensation of heat is experienced with superficial peels.
  •  With medium-depth peels, more intense pain may require local anaesthesia with an anaesthetic cream.
  •  Deep peels result in very intense pain that normally necessitates general anaesthesia.

Post-peeling care

After a superficial peeling, simple hydration is all that is required.14 For medium peel, downtime is necessary for about one week. Post-operative treatment to accelerate healing is required and is based on moisturizers. For deep peels, post-operative care is required for 10 days and unsightliness imposes social isolation during this time; healing care, based on moisturizers or bandages, and daily attentive surveillance are undertaken.14 Photoprotection with sunscreens is recommended for several weeks, especially for medium and deep peels.14 Prophylactic herpes treatment is often administered to patients suffering from frequent infections, especially for medium and deep peels.14

Frequency of application

Superficial peels, especially with AHA and beta-hydroxy acids (BHA), require 4–6 applications, generally 2–4 weeks apart.14 Deeper peeling products are applied only once.15

Histological changes after peeling

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

The histological changes observed evidently depend on the depth of peeling. However, all types of peels cause inflammation and induce healing phenomena that repair the zones damaged by the caustic agent (Table 4).18,19

Table 4.   Depth reached by a trichloroacetic acid peel as a function of the clinical aspect obtained.
Degree of frostingCloudySlightly whiteClearly whiteIntensely and uniformly whiteGrey–whiteGrey
Crimping0±++++±0
Firmness0+++++++++++++++
Oedema00±+++++++++
DepthEpidermisEpidermisPapillary dermisPapillary dermisUpper dermisMedium dermis

Superficial peeling involves the epidermis and the outermost part of the dermis. The epidermis becomes thinner and its regeneration is caused by multiplication of the epidermal cells. New layers of epidermis are produced. In the dermis, an inflammation provokes neocollagenesis.13 Stimulation of the epidermis induces the production of cytokines that, in turn, stimulate the activation of fibroblasts. The fibroblasts produce collagen type 1 and type 4 as well as elastin fibres. Medium peeling removes the epidermis and reaches the papillary dermis. The regeneration of skin is mainly from cells of the hair follicles, which are present deeper than the areas destroyed by the peeling process. New layers of epidermis are formed and collagenesis is stimulated.13

Deep peeling destroys the epidermis, superficial dermis and reaches the reticular dermis. The regeneration of the epidermis is also from cells of the hair follicles. The production of new collagen and ground substance is very important.13 With phenol peeling, a number of modifications have been reported after several weeks.19 In the epidermis, and in comparison with untreated zones, epidermal architecture returns to normal. Melanocytes are present and distributed uniformly. Basal cells contain small melanin grains distributed homogeneously. The histological signs of lentigines and actinic keratosis found in untreated zones are no longer visible. The thickness of the basal membrane is homogeneous. In the dermis, a new sub-epidermal band of collagen and a band 2–3 mm thick appears. It is located above the dermis where elastolysis occurs, the part of the dermis unaffected by peeling. The sub-epidermal band is composed of compact bundles of collagen arranged parallel to the skin surface. New elastic fibres form a network of fine fibres, often parallel to those of collagen. These modifications can be observed up to 20 years after Phenol peeling.19

Mechanisms of action of peels

Superficial peels.  Glycolic acid targets the corneosome by enhancing breakdown and decreasing cohesiveness, causing desquamation.20 Superficial peels with AHA also increase epidermal activity of enzymes, leading to epidermolysis and exfoliation.21 Glycolic acid is extremely hydrophilic and has a low pH that varies with the concentration of the acid (e.g. unbuffered solutions of 80% concentration have a pH of 0.5, 10% concentration has pH 1.7).21 Glycolic acid peels typically need to be properly neutralized to stop the acidification of the skin; applying acid to the skin saturates the ability of cells to resist acidification and excess acid must be neutralized to avoid burning the skin.21 AHA peels can be neutralized by basic solutions, such as ammonium salts, sodium bicarbonate or sodium hydroxide.21

The LHA molecule acts on the corneosome/corneocyte interface to detach individual corneosomes cleanly.22 The corneosome is detached from adjacent corneocytes without fragmentation, suggesting that LHA probably acts on transmembrane glycoproteins. This action occurs at the compactum/disjunctum interface and does not affect keratin fibres or the corneocyte membrane.22 LHA also stimulates renewal of epidermal cells and the extracellular matrix, with an effect that is similar to the effect of the reference compound retinoic acid. In contrast to many other peeling chemicals, LHA has a pH that is similar to that of normal skin (5.5) and does not require neutralization.

Medium peels.  Medium-depth peels, such as TCA, cause coagulation of membrane proteins and destroy living cells of the epidermis and, depending on the concentration, the dermis.21 New, healthy keratinocytes replace abnormal cells and stimulate the skin to produce new collagen.21 The depth of skin necrosis correlates closely with the potency of the medium-depth peel.

Deep peels  Deep peels act in the reticular dermis, while medium-depth peels target the papillary dermis and stimulate new collagen deposition, decrease elastic fibres and increase activated fibroblasts.23,24 Deep peels coagulate proteins, which produces the frosting seen clinically, and produce complete epidermolysis.21 In addition, phenol peels restructure the basal layer by incapacitating melanocytes and inhibiting transfer of melanosomes to nearby keratinocytes.21 Deep peels can also destroy the papillary dermis, restoring the dermal architecture.21

Chemical substances used for peelings

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

Alfa-hydroxy acids

Among superficial peels, the most commonly used product is glycolic acid. It is used in solutions at concentrations varying between 25% and 70% and at a pH between 1 and 3; tolerance is generally good. The higher the concentration and the lower the pH, the more intense the peeling will be, but it remains superficial. Glycolic acid is always used over several sessions (generally 6) several weeks apart. As sessions progress, the concentration of the solution used and application time are progressively increased depending on tolerance and the result obtained after preceding sessions.15 Other AHA exist, including lactic acid,25 pyruvic acid26 and mandelic acid, but are used less frequently.

Beta-hydroxy acids

Salicylic acid has been used for a long time, but is used much less frequently since the advent of peeling with AHA. This superficial peel is employed at weekly sessions for 6–8 weeks.27,28,29 A peel using a lipophilic derivative of salicylic acid, lipo-hydroxy acid (LHA), has recently been introduced.13 It is the newest product in this category. The LHA is used in 5% and 10% concentrations.

Resorcin or resorcinol

Resorcin is generally used in preparations, the most widely used being Jessner’s solution,14 the formula of which is: 14 g of resorcinol, 14 g of salicylic acid, 14 mL of lactic acid, ethanol q.s. 100 mL. This provides a superficial peel14 and the preparation is used in a single session. Some authors combine Jessner’s solution with a 35% TCA peel in the same session to obtain a medium-depth peel.12,30 Resorcin is not used in some European countries.

Trichloroacetic acid

Trichloroacetic acid has been used as a peel for a long time. The depth of peeling depends on the TCA concentration: between 10% and 30% is considered a superficial peel; above 30% provides a medium-depth peel. The concentration used generally does not exceed 50%.14 The depth of the peel depends not only on the concentration, but also on the time of application. The depth reached is precise as a function of symptomatology (Table 1),14,31,32 but requires considerable experience. A TCA peel is thus highly operator-dependant. There is no need to neutralize the product.

Table 1.   Indications and contraindications for peeling procedures
Treatment stepsPeeling agentPeeling level
SuperficialMedium-deepDeep
AHA/BHA/LHATCA 35% or combinationsTCA > 50%, phenol
  1. TCA, trichloroacetic acid; AHA, alfa-hydroxy acids; BHA, beta-hydroxy acids; LHA, lipo-hydroxy acid.

Indications Photoaging  Roughness, yellow stains  Fine lines; keratosis  Solar lentigines Pigmentary disorders  Melasma  Post-inflammatory Retentional acne ± comedone extractionPhotoaging  Fine lines  Wrinkles Pigmentary disorders Superficial atrophic scarsSevere photoaging Pigmentary disorders Scars
ContraindicationsAbsolutePregnant, nursing patients, 6 months isotretinoin treatment Active herpes simplex; cold sores Fitzpatrick skin types V-VIPregnant, nursing patients, 6 months isotretinoin treatment Active herpes simplex; cold sores Fitzpatrick skin types IV–VIPregnant, nursing patients, 6 months isotretinoin treatment Active herpes simplex; cold sores Fitzpatrick skin types IV–VI Phenol: insufficient kidney function
RelativeCold sores: 4–6 weeks after healing Botulinum toxin: 1–2 weeks after Collagen injections: 2 weeks before or after Facial surgery: 6 weeks after oedema Laser: 8 weeks after Electrolysis and dying: 7 days before or after Waxing, depilatories: 3 weeks afterQuestionable patient compliance Regular sun exposure Heavy cigarette smoking Inactive but recurring herpes infections Oral oestrogen intake History of hypertrophic scarring Connective tissue disorders Advanced AIDS stages

Phenol

Phenol is used in solution and there are many formulas.14 Treatment is very painful and requires general anaesthesia or deep sedation. The risk of heart failure requires cardiac monitoring; therefore, hospitalization is obligatory.33 Phenol is used for deep peels and is a difficult product to use. Laser resurfacing is generally preferred now.34

Indications

Indications can be divided into two groups; those for which there is an indisputable consensus and those reported in very rare cases.

Recognized indications

  • Wrinkles. Peels are part of the classical strategy for managing skin ageing.14,34,35 Superficial peels act on fine superficial lines (figs 2 and 3). Some peels can modulate both epidermal and dermal signs of ageing, especially through epidermal thickening and dendrocytic hyperplasia. Medium-depth and deep peels result in neocollagenesis and so are active against medium-sized wrinkles (figs 4–6). Very few comparative studies on peels have been conducted. In one, LHA peel (without neutralization) was compared with glycolic acid (20% and 50% with neutralization) in a split-face study of mild to moderate facial ageing. Wrinkle improvement was noted in 41% on the LHA side and 30% on the glycolic acid side.36
  • Complexion, melasma and lentigines. (1) Superficial peels result in a regular epidermal structure with uniform distribution of melanin and the elimination of melanin accumulations.18 Clinically, superficial peels impart a radiant complexion, treat melasma at the dermal–epidermal junction and improve lentigines.14,32 In the study comparing LHA and glycolic acid discussed above, 46% of women showed an improvement in pigment disorders on the LHA side vs. 34% on the glycolic acid side.13 (2) Medium-depth or deep peels are also effective on lentigines and improve the complexion.14,32 However, they are contraindicated for melasma as they may cause post-inflammatory hyperpigmentation that aggravates the initial symptomatology. Precautions associated with their use are proportional to the darkness of the skin to be treated.36,37
  • Scars. Medium-depth and occasionally deep peels are used on relatively shallow scars to elevate the base of the scar by neocollagenesis and to lower the edges by the abrasion they cause. They are often proposed to treat regular shallow acne scars.14,38–40
  • Actinic keratosis. Some authors have proposed using medium-depth or deep peels to treat profuse actinic keratoses.12,13,41 Recently, Hantash and colleagues conducted a prospective, randomized, 5-year trial to evaluate the ability of chemical peeling (30% TCA) as a prophylaxis against actinic keratoses.42 The results showed that treatment with TCA peels significantly reduced actinic keratoses and was associated with a trend towards longer time to development of new actinic keratoses compared with that of a control group (P = 0.07).42
  • Acne: Some authors have proposed superficial peels as adjuvant treatments for acne (fig. 7); they act as comedolytic agents43–47 but have no effect on seborrhoea.46 Superficial peels can result in improvement in both skin appearance and texture,29 but have very few effects on atrophic or hypertrophic scars; they may also improve penetration of topical acne therapies.45 Best results may occur when these peels are used in patients with oily skin and seborrhoea. Peels should be used as an adjunctive treatment to the appropriate topical and oral medications. Depending on the climate, the type of peel may be rotated on a seasonal basis. Acne flare is possible with peels, and patients should be counselled about the possibility of flare so that they do not become discouraged.
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Figure 2.  Clinical effect of a single treatment with lipo-hydroxy acid.

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Figure 3.  Clinical effect after four treatments.

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Figure 4.  Clinical effect of deep phenol peel on wrinkles (baseline and 3 months post-peel). Photos courtesy of Dr Torsten Walker.

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Figure 5.  Clinical effect of deep phenol peel on wrinkles (baseline and 7 months post-peel). Photos courtesy of Dr Torsten Walker.

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Figure 6.  Clinical effect of deep phenol peel on wrinkles (baseline and 11 months post-peel). Photos courtesy of Dr Torsten Walker.

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Figure 7.  Clinical effect of trichloroacetic acid 25% with Jessner’s solution. Photos courtesy of Dr Torsten Walker.

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A recent split-face, blinded study compared a series of six glycolic acid 30% peels on one side of the face vs. six salicylic acid 30% peels on the other side in patients with facial acne (n = 20).47 Both treatments were effective, but the effect of salicylic acid was sustained longer and this peel was associated with fewer side-effects compared with that of glycolic acid.47 In acne prone women, LHA reduced both the number and the size of microcomedones, the acne precursor lesions.48 The same study also showed that unplugging the follicle was associated with lower bacterial loads in the follicle and a reduction in follicular size.48 We can hypothesize that the lipophilic form of salicylic acid could increase the effect of superficial peeling; this effect may be attributable to a better penetration into the sebaceous follicle.

Other indications

Peeling has been proposed to treat flat warts,26 Pseudofolliculitis barbae,37 trichoepitheliomas,49 rhinophyma,50 generalized linear epidermal naevus51 and tumour prophylaxis in xeroderma pigmentosum.52 There is relatively little documentation on these indications, which are sometimes based on an old and unconfirmed publication. Considerable caution is thus required in these cases. Anecdotally, the authors have had good experience with superficial peels for keratosis pilaris, particularly on the arms, legs and backs. Peels may also be useful to enhance the results of laser therapy or other concomitantly used procedures. The different indications and contraindications are summarized in Table 1.

Side-effects management and prevention of complications

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

All peels should be managed with care to minimize the potential for side-effects; the level of expertise in administering peels is vitally important to ensure a good outcome. Generally, the depth of peel correlates with the potential for side-effects and the benefit/risk ratio changes with increasingly deeper peels. Superficial peels very rarely cause complications, which are usually not severe – transient mild hyperpigmentation, redness during the first night and a flare-up of pimples have been reported.14 Medium peels cause marked redness for several days, followed by desquamation that can be quite significant. There is a high risk of hyperpigmentation and solar lentigines following treatment. Therefore, a stringent photoprotection with sunscreens is recommended for several weeks. Because of the risk of hyperpigmentation, medium-depth peels are unsuitable for phototype V or VI patients. There is also an increased risk of herpes infection.6

For deep peels, the risk of complications is significant, particularly post-operative infections and, more importantly, pigmentation problems such as frequent early transient hyperpigmentation followed by hypopigmentation, or even total and permanent achromia. Deep peels are, therefore, performed only in patients with light phototypes. These are currently used to a lesser extent because of the greater risk of complications. In a recent study, a rate of cardiac complications (most notably arrhythmia) of 7% has been reported for phenol peels.6 The different side-effects and complications are summarized in Table 2.

Table 2.   Side-effects and complications for peeling procedures
 Peeling level
SuperficialMedium-deepDeep
AHA/BHA LHATCA 35% or combinationsTCA >50%, phenol
  1. TCA, trichloroacetic acid; AHA, alfa-hydroxy acids; BHA, beta-hydroxy acids; LHA, lipo-hydroxy acid.

Potential side-effects/complicationsRedness Transient hyperpigmentation Pimples Redness Herpes Hyperpigmentation LentiginesPain Redness Herpes Transient hyperpigmentation Infection Hypopigmentation Permanent achromia Heart failure (phenol)

Conclusion

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References

Chemical peels represent a flexible and useful tool for improving skin texture and the effects of ageing. Peels are available in a variety of formulations that allow the clinician to individualize therapy to the patient’s presentation. This technique is indicated for a range of skin problems, including wrinkles, acne and pigmentary changes. In addition, peels may be used with other techniques as part of a multimodality approach to improve skin texture and resurface skin.

Three major points are essential for successful chemical peels:

  • • 
    Clinical concept– peeling is more than “an ablative technique”: the process uses the inflammatory reaction and dermal stimulation proactively to modify the skin.
  • • 
    Pre- and post-procedure skin– never underestimate the role of the pre- and post-treatment for the efficacy of the peel. It will determine the level of re-epithelialization, remodelling effects as well as scaring/recovery time.
  • • 
    Side-effects– the level of expertise of a dermatologist is crucial for the rate of side-effects and for the final peel results. Superficial peels are easy to perform and their benefit/ratio risk is very good.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. History
  5. Classification
  6. General principles of peeling procedures
  7. Histological changes after peeling
  8. Chemical substances used for peelings
  9. Side-effects management and prevention of complications
  10. Conclusion
  11. Acknowledgements
  12. References