A perspective on what’s new in chemical peels

INTRODUCTION

Chemical peels are important procedures in a cosmetic or aesthetic practice as they are versatile and cost-effective. The concept of skin peeling by chemicals to beautify the skin has been used since time immemorial. Cleopatra used sour milk, containing lactic acid, and French women used old wine containing tartaric acid as beauty baths. With the advent of newer peels and newer combinations, there has been a resurgence of their popularity in recent times. According to the American Society of Plastic Surgeons, they are among the top five minimally invasive cosmetic procedures in practice.^[1] Chemical peels are basically cutaneous resurfacing procedures, that cause a controlled chemical exfoliation of the skin, followed by regeneration and remodeling of the epidermis and dermis leading to improved appearance of the skin.^[2] Some of the newer peels have added adjuvants that do not cause obvious peeling; hence, “chemical rejuvenation” is a more appropriate term.

VALUE OF PEELS IN AESTHETIC PRACTICE

The resurgence of popularity of peels among dermatologists, plastic surgeons, and estheticians is due to its several advantages. They are simple office procedures, easy to learn and practice, minimally invasive with little downtime, that perfectly suit today’s busy lifestyles. Unlike lasers, they do not require equipment and costly maintenance and more importantly have minimal complications, even in skin of color. The long-term experience with chemical peels has shown them to be safe and effective for a variety of common conditions such as dyschromias, photoaging, and acne. A wide array of peeling agents is now available; hence, treatment can be individualized, according to skin type.

CLASSIFICATION OF PEELS

Chemical peels are traditionally classified according to the depth of peeling as very superficial, superficial, medium depth, and deep peels [Table 1]. However, the depth can be variable, depending on the formulation of the peeling agent, amount of free acid, pre-peel skin preparation, skin condition, and method of application of the peel. It is preferable to standardize the method of skin preparation, priming agents, and application with the same formulation to achieve the desired depth.

INDICATIONS

Chemical peels can be used for various aesthetic and medical conditions [Table 2] acne, hyperpigmentation, photoaging, and skin rejuvenation are the main indications. Very superficial peels exfoliate the stratum corneum only, leading to smooth, translucent skin with a glow. These are called as lunchtime peels, party peels, or glow peels.

CONTRAINDICATIONS

Absolute contraindications to chemical peels include active infection, particularly herpes simplex, open wounds, and allergy to peeling ingredients. Relative contraindications include recent sun tanning, photosensitizing medications, and pre-existing inflammatory dermatosis such as psoriasis, atopic dermatitis, pregnancy, radiation therapy, and unreliable patients. It was previously advocated that all resurfacing procedures are contraindicated with concomitant use of isotretinoin, due to increased risk of scarring. However, the recent evidence points that they are safe, particularly superficial, and medium depth peels, while deep peels should be avoided.^[3,4]

TYPES OF PEELS AND NEWER PEELS

Peels can be single agent peels, called as monopeels or a combination of agents compatible in a single formulation called as combination peels [Table 3].^[5] The classic monopeels are salicylic acid (SA 20–30%), glycolic acid (GA 20–70%), and trichloroacetic acid (TCA 15–50%). Other newer monopeels peels include mandelic acid (10–40%), pyruvic acid, lactic acid, ferulic acid, and retinoic acid. The classic combination peel is the Jessner’s peel (Lactic acid, SA and resorcinol). Phenol peel is also a combination of phenol with croton oil. The newer combination peels include modified Jessner’s peel (lactic acid, SA and citric acid), salicylic - mandelic acid, VI peel (TCA, SA, tretinoin, phenol, and citric acid), polyhydroxy acids, lipohydroxy acids (LHA), and combination skin lightening peels.

Peels may also be classified according to their formulation as solution based peels, gel based peels and peeling pastes, creams, or ointments. Most of the chemical peels are available as solutions. Examples of solutions are glycolic acid 70%, TCA 25%, SA 20%, Jessners solution, etc. Gel based peels are formulated as gels and are indicated for sensitive skins as they deliver the active agent slowly into the skin and hence are better tolerated.^[2] They cause minimal irritation and exfoliation, for examples, are mandelic acid 40% gel, salicylic-mandelic acid combination gel, lactic acid 90% gel, etc. Chemical peels are also available as pastes, ointments or creams. Examples are Unna’s paste containing zinc oxide 60%, SA 20% ointment, and retinol cream.

The alpha hydroxy acids (AHA) are a group of acids that include glycolic acid, which is the older one, and mandelic acid, lactic acid, tartaric acid, citric acid, and malic acid, which are the newer peels. AHAs are water soluble and act as exfoliators on the skin surface. They are useful in persons with dry, rough skin, and in conditions such as keratosis pilaris. It is important to use sunscreen during the peeling period as they can cause photosensitivity. Beta hydroxy acids are a group of acids that include SA and some forms of citric acid. They are useful in conditions with oily skin. LHA is derived from SA. Being more fat soluble, it penetrates the skin more slowly and is useful for treating acne in patients with sensitive skin.^[6] Polyhydroxy acids are a group of acids that includes lactobionic acid, gluconolactone, and maltobionic acid. They have a larger molecular structure as compared to AHA, penetrate the skin more slowly, gently exfoliate the skin and are useful for sensitive skins and conditions such as rosacea. Mandelic acid is an AHA with a large molecular weight. It penetrates the skin more slowly, is less irritating, and also has skin lightening properties and antibacterial action. Thus, it is a very useful peel for acne, melasma, and hyperpigmentation, particularly in sensitive skins.

NEWER WAYS TO PEEL

Chemical peels are versatile procedures and newer modifications have further increased their versatility.^[5]

PRIMING AND PRE-PEEL CARE

Pre-peel care or priming is done before chemical peeling. Priming aims at thinning the stratum corneum to enhance penetration of chemical agents, accelerate healing, and reduce the incidence of post-inflammatory hyperpigmentation (PIH). It is particularly important in darker skins, Fitzpatrick Type IV-VI that are prone to PIH. Priming should begin at least 2–4 weeks before the chemical peel and stopped 3–5 days prior.^[3,8] Patients should avoid UV exposure and apply a broad-spectrum sunscreen that blocks both UVA and UVB each morning. Sunscreen should ideally be started at least 3 months before the procedure and continued thereafter. Tretinoin cream (all-trans retinoic acid) is a useful priming agent that causes decreased epidermal adhesion, resulting in thinning of the stratum corneum, and enabling the peeling agent to penetrate the skin more rapidly and deeply. Tretinoin also enhances epithelial differentiation and accelerates epithelial proliferation, hence hastening re-epithelialization. Hydroquinone 2–4% cream reduces the risk of PIH and should be initiated at least 2 weeks before a chemical peel. Other topical agents that are used as priming agents include glycolic acid 5–10%, salicyclic acid 5–10%, kojic acid 1–4%, azelaic acid, and topical corticosteroids. Patients should be instructed to avoid waxing, electrolysis, and dermaplaning for a minimum of 3–4 weeks before chemical peeling. Individuals with a history of recurrent herpes simplex virus infection should be commenced on systemic antiviral treatment before medium-depth and deep chemical peeling and continued for 7 days post-procedure.^[8]

POST-PROCEDURE CARE

Good post-peel care is essential for recovery of the skin and preventing complications. The patients should be instructed to wash the face gently with a non-soap cleanser and to avoid rubbing, scrubbing, scratching, or picking their skin. A bland emollient and sunscreen should be applied regularly to the skin until peeling is complete. Ice packs may be used for mild edema and burning, while topical steroids may be required for severe edema and discomfort. Thereafter the products used in pre-peel care should be restarted.

CHEMICAL PEELS IN ACTIVE ACNE

Chemical peels are being increasingly used in the management of acne. They are good adjuvants in active acne. SA, mandelic acid, retinoic acid (yellow peel), glycolic acid, TCA, Jessners peel, pyruvic acid, azelaic acid, and combination peels are useful peels for acne. Chemical peels in acne offer several benefits. Since many peels like SA, are lipophilic, they can easily target the sebaceous glands. Comedones can easily be extracted, post-acne pigmentation, and oiliness can be reduced and there can be improvement of superficial post- acne scars. In a study of 36 patients, Fitzpatrick Type IV-V, Jessner’s solution (JS) was compared with SA 30% in the management of acne vulgaris and post-acne hyperpigmentation.^[10,11] Three sessions were performed every fortnight. Significant improvement was observed in the inflammatory, non-inflammatory lesions, and in the pigmentation. There was no difference between the two reagents, though SA was superior for the non-inflammatory lesions and led to faster improvement in inflammatory lesions. Side effects such as burning, exfoliation, and acneiform eruptions were mild and transient. PIH was observed in one patient treated with JS. Thus, chemical peels were safe and effective even in darker skin types. In a study of 45 patients, a chemical peel containing SA, pyruvic acid, and retinoic acid (DefinisseTM classic peel by Relife) was applied at 3 week intervals for four sessions.^[11] Patients were evaluated by Michaelson’s score and Subject Global Aesthetic Improvement Scale. Improvement was seen in 96% patients. In this combination peel, SA and pyruvic acid are lipophilic and also have an anti-inflammatory effect, while topical retinoic acid allows a better penetration of the other acids into the dermis. A study comparing 45% mandelic acid with 30% SA found both were equally efficacious, but MA had was better tolerated, while SA was more efficacious in treating non-inflammatory lesions.^[12] Comparative study of efficacy and safety of 45% mandelic acid versus 30% SA peels in mild-to-moderate acne vulgaris. Another study compared azelaic acid with pyruvic acid in adult acne and reported that both peels were equally effective A review of chemical peels in active acne concluded that both glycolic acid and SA are effective and well tolerated, with SA showing a faster response.^[13]

CHEMICAL PEELS IN MELASMA AND HYPERPIGMENTATION

Chemical peels are efficacious in the management of melasma and are often used as second line of treatment. Sahu and Dayal conducted a study on 90 patients with melasma and concluded that 15% TCA and 30% GA peel were equally effective and superior than 92% lactic acid peel in treatment of epidermal melisma.^[14] They also suggested that 30% GA peel is best among the three peels for melasma in Indian patients. Bhardwaj et al. reported their investigations on the mode of action of chemical peels to treat hyperpigmented and photoaged skin.^[15] They observed that besides an exfoliant action, a combined TCA-lactic acid peel strongly inhibits tyrosinase, collagenase and elastase, leading to reduced pigment, and promoting increased collagen and elastin.

CHEMICAL PEELS IN PHOTOAGEING

Medium depth chemical peels are also useful to treat extrinsic and intrinsic ageing. In a comparative study of GA 70% with TCA 15% versus TCA 35%, it was observed that both peels were effective. TCA 35% was more effective but had lower tolerability.^[16]

NEWER INDICATIONS FOR CHEMICAL PEELS

Chemical peels have been used as adjuvant therapies for keratosis pilaris, striae distensae, acanthosis nigricans, macular amyloidosis, PIH, rhinophyma,^[17] repair of ear lobe,^[18] and surface nail abnormalities.^[19] Low strength peels have also been used 2–4 weeks before lasers to prevent PIH. A recent review on chemical peels as field therapy for actinic keratosis (AK) reported that chemical peels were effective in reducing AK counts, with minimal adverse effects. It was useful in diffuse widespread lesions and may also be potentially useful in prevention of additional AK formation and development of keratinocyte carcinomas.^[20]

CHEMICAL PEELS IN MALES

The demand for aesthetic procedures in males has increased tremendously. Male skin is thicker and has more pilosebaceous activity, hence may require more sessions, or higher strength peels. However, they are less likely to be compliant with topical applications and avoidance of sun exposure. Common indications for chemical peels in men include acne vulgaris, acne scarring, melasma, actinic keratosis, photodamage, rosacea, keratosis pilaris, and periorbital rejuvenation.^[21]

PERIOCULAR PEELS

Chemical peels are been increasingly used for rejuvenating and treating hyperpigmentation in the periocular area. Glycolic acid at a concentration of 20–70% is the most common agent used. The effect of glycolic peel depends on the time it is left on skin. Trichloroacetic acid has also been used for rejuvenation. In a comparative study, 20% glycolic acid peeling was more effective than 15% lactic acid and 12% ferulic acid performed at 3 weekly intervals, though ferulic acid was better tolerated.^[22] In another study, three sessions of 30% LA peel appeared to be better, more effective and better tolerated than 20% GA peeling used 3 weeks apart in type four skin.^[23] Erythema, burning, tearing, scaling, and transient darkness were the transient complications observed.

LIP PEELS

Lip peeling is a recent addition in the rejuvenation of the lips. It can help in improving the surface texture, pigmentation, and also to some extent act as a lip enhancer. Indications for lip peeling include lip rejuvenation due to photodamage, lip pigmentation, rough texture, and wrinkles. Mandelic acid, lactic acid, and glycolic acid are the preferred peels on the lips for pigmentation and rejuvenation. Phenol peels are more potent deep peels and are also being used as lip enhancers. The advantage of chemical peeling on the lips over fillers is that additionally they have an anti-aging effect by causing epidermal rejuvenation, improving lip wrinkles, and pigmentary abnormalities caused by photodamage.^[24]

BODY PEELS

Although chemical peels are traditionally most commonly applied on the face, they are being increasingly used in other body areas, including the hands, feet, decolletage area, and trunk to treat various conditions such as uneven skin tone and texture, fine lines, and actinic damage. The major difference between facial peels and body peels is that healing is slower and unpredictable in the non-facial regions due to lesser concentration of appendageal structures. Risk of systemic absorption is greater due to application on larger surface area.

The commonly used agents are glycolic acid, lactic acid, mandelic acid, and trichloroacetic acid. The classic body peel is the Cook’s peel, which is a sequential peel of glycolic acid 70% gel followed by TCA 40% lotion.^[25] It has been used to treat lentigines, actinic keratoses, poikiloderma and photodamaged skin on the chest and decollete. Combination of glycolic, lactic and mandelic acids have been used to treat keratosis pilaris. A study reported that glycolic acid 50–70% significantly improved follicular hyperpigmentation in patients with keratosis pilaris after 4 sessions, but there was no significant difference at the 5-year follow-up compared with pretreatment values.^[26] Other indications of body peels include truncal acne, acanthosis nigricans, frictional melanosis, PIH, and striae.

NAIL PEELS

Chemical peeling of the nail is a recent concept. It has been used for improvement of surface abnormalities, such as rough, dull, discolored, hyperkeratotic, irregular surface abnormalities of the nails, and trachynychia. In an initial study, 70% glycolic acid was applied for 45 min in 22 patients with dry rough nails as a single session. There was good improvement in 80%, average in 10%, whereas 10% were non-responsive.^[27] In another right-left comparative study in 15 patients, 70% glycolic acid versus combination peel of phenol 8% with 15% TCA five patients showed good improvement, seven showed moderate, while three responded poorly. Two patients developed leukonychia due to prolonged exposure to glycolic acid.^[28] Another recent study used the black peel containing a combination of black acetic acid 50%, SA 0.5%, tetrahydrojasmonic acid 6%, 10% bio sulfur, and 0.1% potassium iodide, in combination with 8% ciclopirox olamine in two patients with onychomycosis and comorbidities and reported a favorable response at 6 months.^[29] Proper precautions regarding protection of the cuticles while applying the peel is essential. Further studies are required to prove utility and indications of chemical peels in nail disorders.

COMBINATION PROCEDURES

Chemical peels have also been used in combination with other procedures such as micro needling, microdermabrasion, lasers, botulinum toxin, and fillers for enhanced results in the management of acne scars, pigmentation, photoaging, and skin rejuvenation.^[29] A study conducted in 60 patients concluded that combination of micro needling and Jessner’s solution chemical peel showed better clinical improvement in treating atrophic acne scars as compared to micro needling and chemical peels alone.^[30] In a series of seven patients with Nevus of Ota, combination of 1064-nm Q-switched neodymium-doped yttrium-aluminum-garnet laser with modified Jessner’s peel showed more than 50% reduction in pigment in a majority of patients in eight sessions. The authors concluded that a significant reduction in pigmentation was faster with fewer sessions and reduced cost.^[31]

HOME PEELS

The desire to have a smooth flawless skin has created a rapidly growing market for products that can deliver a little more than topical creams, with minimum downtime. The internet is flooded with a lot of information and products for home-based peels. The practitioner should be aware of these products as patients often ask advice on the selection and usage of these products. They are also useful for initiation of treatment as advanced priming agents and as maintenance therapy after professional chemical peels. Their popularity has further increased during the COVID 19 pandemic and the lockdown. Most of these products contain similar products as physician grade peels, but in a lower concentration. Some examples are 5–10% glycolic acid, 10–20% lactic acid, 10–15% SA, 10–15% mandelic acid, <1% retinol, and lipohydroxy acids. They are available as solutions, serums, medicated pads, masks, and creams. Enzyme peels derived from fruits such as papaya and pumpkin peels are popular ingredients in home peels. They gently exfoliate the skin and are better tolerated. The disadvantage of home peels is that though convenient, overenthusiastic, unsupervised use can result in irritation and complications.

COMPLICATIONS OF CHEMICAL PEELS

Chemical peeling is a relatively safe procedure. Appropriate patient selection, consistent pre-procedure, and post-procedure care minimizes the risk.^[32–34] However, side effects may occur, which are mostly mild, rarely severe [Table 4].^[33,34] A survey of Australian dermatologists, reported that hyperpigmentation (67%), persistent erythema (52%), edema (37%), and acne or folliculitis were the most common complications seen.^[35] Excessive irritation and burning are the common early complications and can be managed with moisturizers and topical steroids. Short course of oral steroids may be given if there is edema, particularly in the periocular region. Intralesional steroids may be indicated in areas of impending hypertrophic scarring. Indicators of hypertrophic scarring include persistent erythema, textural abnormality, and more common on the mandibular area. Prolonged erythema may be treated with pulsed-dye or dual wavelength vascular lasers. PIH can occur in darker skin types or with prolonged sun exposure following peels. It is managed by skin lightening agents.

CONCLUSION

Chemical peels are ideal for patients looking to improve skin texture and tone. They are simple, cost effective office procedures, with little downtime. Newer peels, newer ways to peel and combinations with other procedures keep chemical peels among the top five minimally invasive aesthetic procedures performed globally.