Score	Description
1	Absent: No visible fold; continuous skin line. Amelioration with TCA peels
2	Mild: Shallow but visible fold with a slight indentation; minor facial feature; improvement in skin texture with TCA peels
3	Moderate: Moderately deep folds; clear facial feature visible at normal appearance but not when stretched. Excellent correction with phenol peels
4	Severe: Very long and deep folds; prominent facial feature; less than 2 mm visible fold when stretched. Significant improvement expected with combined peels
5	Extreme: Extremely deep and long folds detrimental to facial appearance; 2–4 mm visible V-shaped fold when stretched. Unlikely to have satisfactory correction with medium and deep peelings alone

Table 13.1 Correlation among skin diseases and suggested peeling approach

Skin disease	Diagnostic method	Suggested approach
Comedonal Acne-papulo-pustular	Global score^a	+++Salicylic acid +++Pyruvic acid +Glycolic acid +Mandelic acid

Melasma MASI score^b

+++Salicylic acid

+++Pyruvic acid

++Glycolic acid

+Kojic acid +Retinoic acid

Photoaging Wrinkle severity index^c

+++Retinoic acid

+++Trichloroacetic acid (TCA) 30%

Xantelasma Clinical evaluation

+++TCA 30%

Acne scars
Box scar Goodman & Barron classification^d

+++TCA CROSS +++TCA 30%

++Glycolic acid ++Salicylic acid with TCA 25%

++Resorcinol

++Jessner’s solution

Rosacea Clinical evaluation

+++ Salicylic acid

+++Pyruvic acid

+Azelaic acid

Lentigo simplex Clinical evaluation

+++TCA 30%

++Salicylic acid

Actinic keratosis Clinical evaluation

+++TCA 10–30%

++Salicylic acid

++Glycolic acid 70%

Chicken pox Goodman & Barron classification^d

+++TCA CROSS

^a Doshi A, Zaheer A, Stiller MJ 1997 A comparison of current acne grading systems and proposal of a novel system. International Journal of Dermatology 38:416–418

^b See Box 13.1

^c Day DJ, Littler CM, Swift RW, Gottlieb S 2004 The wrinkle severity rating scale: a validation study. American Journal of Clinical Dermatology 5(1):49–52

^d Goodman GJ, Baron JA 2006 Postacne scarring: a qualitative global scarring grading system. Dermatologic Surgery 32:1458–1466

Patient expectations and lifestyle must also be evaluated. During the consultation, if it is evident that the patient overestimates the benefits that can be achieved or cannot tolerate long post peeling care and recovery time (as with medium-depth TCA peels), the physician must recommend an alternative treatment. Numerous skin disorders can be improved with chemical peeling.

Indications

• Acne

In active acne, peels can be utilized due to their anti-inflammatory and keratolytic properties. These effects can enhance the efficacy of topical treatments and increase the patient’s compliance to therapeutic regimens. The keratolytic effect improves skin smoothness and promotes penetration of topical drugs by exfoliating the stratum cornuem. In this way it is possible to obtain a rapid improvement of comedonal and papulo-pustular lesions. However, patients with nodulocystic acne should be cautioned that only limited improvement with chemical peels is likely.

• Acne scars

The best results are achieved in macular scars. Ice pick and rolling scars cannot disappear completely and need sequential peelings combined with homecare treatment with topical retinoids and alpha hydroxy acids. For the deepest ice pick scars, phenol peels can be very useful but require monitoring.

• Melasma and hyperpigmentations

Chemical peels are very effective in treating melasma. To achieve optimal results, patients must adhere to home skin care regimens that include depigmentating topical agents and broad spectrum sunscreens. In dermal melasma or solar lentigines, peelings can be incompletely effective. Very circumscribed cryotherapy or intense pulsed light or laser can be employed to disperse residual pigmentation. Nevertheless, chemical peels can be utilized when lentigines are widespread and lightly pigmented to obtain an overall reduction in pigmentation prior to pulsed light or cryotherapy. In our hands, 30% salicylic acid is best suited for this indication.

• Xanthelasma

Focal chemical peeling is an effective treatment for xanthelasma in the majority of cases. In particular, we have found that xanthelasma lesions can be ‘debulked’ with chemical peels prior to excisional surgery. Our favorite agent for this indication is trichloracetic acid at a concentration of 30%. In the literature, xanthelasma has been successfully treated with higher concentrations of TCA (90–100%) and full strength (100%) bichloracetic acid (BCA).

• Expected results

The level of improvement can vary with regard to different diseases and individual patients. With training and experience, one will be able to select the most appropriate peel type(s) to address a patient’s specific skin condition. For example, a patient with ice-pick acne scars can expect only mild improvement in the scars even if skin texture is remodeled. Conversely, a patient with isolated box car scars can obtain a significant improvement with focal application of TCA at 50–90% to individual scars. This technique called TCA CROSS (chemical reconstruction of skin scars) can produce more than 70% improvement of visible scars with homogeneous tightening of the skin.

In case of melasma and lentigines, chemical peels are usually performed as a series and may need to be repeated after summer or extensive unprotected sun exposure.

To control comedonal acne and seborrhea, several sessions of weekly light chemical peels are performed over the course of a month. For photo rejuvenation, periodic light chemical peels can exfoliate the hyperkeratotic stratum corneum and improve skin brightness and texture. Concentrations of the peeling agent are titrated upwards as the patient tolerates. Today’s patients desire cost-effective procedures which produce reliable results and have minimal associated side effects and downtime. For many indications, chemical peels are just that.

Treatment Approach

The general principles of chemical peeling are easily remembered. Be familiar with the peeling agent you are using, and remember the microanatomy of the skin you are peeling. Thin skin peels faster than thick skin. The key factors which determine the depth of the wound that you create with the peeling agent (superficial, medium or deep) depends on three main factors: (1) the concentration of the agent; (2) the amount of pressure applied to the skin; and (3) the duration time of application.

Skin preparation is very important for superficial and medium peels. We feel that daily use of topical retinoid for 3–6 weeks before the procedure creates a better and more even penetration of the peeling solution in patients with sebaceous and hyperkeratotic skin. In thin-skinned patients, we do not utilize this retinoid regimen.

Standard baseline photography and an informed consent are always obtained prior to the procedure. Since the choice of the peeling agent is a very important step, we have recently developed a flowchart that can help doctors in the evaluation and management of potential candidates for chemical peels (see Figure 13.1).

Figure 13.1 Flowcharts of potential candidates for chemical peels and peeling principal indication

• Major determinants

Table 13.2 summarizes the main factors that can influence therapeutic efficacy and side effects of different chemical peels.

Table 13.2 Main factors that can influence therapeutic efficacy and side effects of different chemical peels

Chemical peel	Advantages	Disadvantages
Pyruvic acid	Very mild erythema Mild desquamation Short postoperative period Can be used in skin types III and IV Excellent for acne	Intense stinging and burning sensation during application Requires neutralization Pungent and irritating vapors for the upper respiratory mucosa
Salicylic acid	Excellent for acne Given the appearance of the white precipitate, uniformity of application is easily evaluated The peel induces an anesthetic effect that increases patient tolerance Established safety profile in patients with skin types I–VI	Minimal efficacy in patients with significant photodamage Limited depth of peeling
Resorcinol	Easy to perform Uniformity of application and penetration Useful in acne, postinflammatory hyperpigmentation and melasma Not painful (the burning sensation during the peeling is usually mild)	Cannot be used in summer Resorcinol may cause allergic and toxic reactions Unsafe in Fitzpatrick skin type higher than V Desquamative effect aesthetically unacceptable
Trichloracetic acid	Low-cost procedure Uniformity of application and penetration Evaluation of the frost, permits easy to modulate depth of penetration	Stinging and burning sensation during the application High concentrations are not recommended in skin types V and VI Hypo/hyperpigmentation can occur
Combination peels: Salicylic acid + TCA	Efficacy in all skin types Well tolerated in darker racial/ethnic groups Most beneficial in treating recalcitrant melasma and postinflammatory hyperpigmentation	Increase penetration of superficial peeling Increased desquamation in some patients lasting up to 7–10 days Postinflammatory hyperpigmentation more common than with salicylic acid peeling alone
Glycolic acid	Very mild erythema Mild desquamation Short postoperative period Useful in photodamage	Burning sensation and erythema during application No uniformity of application Requires neutralization Necrotic ulcerations if time of application is too long and/or skin pH is reduced Cautious application in patients with active acne
Jessner’s solution	Excellent safety profile Can be used in all skin types Substantial efficacy with minimal ‘downtime’ Enhances the penetration of TCA peel	Concerns regarding resorcinol toxicity, including thyroid dysfunction Manufacturing variations Instability with exposure to light and air Excessive exfoliation in some patients

• Patient interview

To better select the right patient for the right peel it is important to obtain a detailed history that evaluates all potential risks linked to the peeling agents. It is important to identify all potential factors that may adversely affect the outcome of a peel and fully characterize a patient’s skin type and propensity to scar and hyperpigment (see Table 13.3).

Questions	Possible answers and discussion
Do you have sensitive skin?	Sensitive skin can develop adverse reactions even with superficial peels at low concentration.
Are you pregnant or breast-feeding?	Some peels, such as salicylic acid, should be avoided in pregnant and breast-feeding women.
Are you allergic to topical or systemic drugs?	Patients with glycolate hypersensitivity cannot be treated with glycolic acid; allergy to resorcinol, salicylic acid, or lactic acid are absolute contraindications to Jessner’s solution
Have you been treated with isotretinoin therapy within the last 6 months?	This is a contraindication to deeper chemical peels
What do you expect from this treatment?	Patients should not have unrealistic expectations
Do you have recurrent herpes simplex virus infection?	History of recurrent herpes simplex virus infection requires systemic prophylaxis with antivirals starting a day before the procedure and continuing for 10 days until full reepithelilization

Treatment Techniques

• Glycolic acid

Glycolic acid acts by thinning the stratum corneum, promoting epidermolysis and dispersing basal layer melanin. It increases dermal hyaluronic acid and collagen gene expression by increasing secretion of IL-6.

Glycolic acid is a useful adjunctive therapy in a variety of conditions including photodamage, acne scars, striae distensae, pseudofolliculitis barbae, hyperpigmentation disorders, actinic keratoses, fine wrinkles, lentigo, melasma and seborrheic keratoses. It may also reduce UV-induced skin tumor development and has been successfully utilized in exfoliative conditions such as ichthyosis, xeroderma and psoriasis. Concentrations and number of treatments depend on the diagnosis. The appearance of striae distensae alba on the abdomen or thighs can be improved with topical 20% glycolic acid daily. In melasma, a series of three monthly 50% glycolic acid peels can minimize unwanted pigmentation. In patients with comedonal acne, we typically perform 70% glycolic acid peels with an application time of 2–7 minutes. Glycolic acid peels are also helpful to reduce seborrhea and to prepare skin for more extensive photo rejuvenation. Sequential application of a Glycolic acid peel followed by TCA produces a uniform a medium-depth peel. This can be performed as a single procedure to treat actinic keratoses, mild rhytides, pigmentary dyschromias or depressed scars.

Side Effects, Complications and Alternative Approaches

Side effects, such as temporary hyperpigmentation or irritation, are not very common with superficial glycolic acid peels. Some studies demonstrate that the level of skin damage with glycolic acid peel increases in a dose- and time-dependent manner. Lower doses (1 and 3 mg/cm²) of glycolic acid caused erythema and eschars, whereas higher doses (5 and 7 mg/cm²) caused redness, edema and necrotic ulceration. Systemic effects are rare.

• Jessner’s solution

First formulated by Dr. Max Jessner, this combination of resorcinol (14 g), salicylic acid (14 g), and lactic acid (85%) in ethanol (95%) is an excellent superficial peeling agent. The advantage of this formulation is the synergistic effect of keratolytic agents and phenolic skin-lightening agent (resorcinol). Jessner’s peels have long been used to treat hyperkeratotic epidermal lesions, acne, melasma, postinflammatory hyperpigmentation, lentigo, freckles, and photodamage.

Because of its excellent safety profile, Jessner’s solution can be used in all skin types and it has substantial efficacy with minimal ‘downtime’. Similar to glycolic acid, Jessner’s solution can be used to enhance the penetration of TCA.

Jessner’s solution can be used in postinflammatory hyperpigmentation, comedonal, to moderate inflammatory acne. In more extensive photoaging, a Jessner’s peel in combination with TCA 35% can be employed. In darker skintypes we prefer to use 35% TCA only.

Side Effects, Complications and Alternative Approaches

Despite concerns regarding resorcinol and salicylate toxicity, Jessner’s solution is extremely well tolerated and has minimal side effects. Although cases of thyroid disease have been reported, a recent toxicological review on the risk of Jessner’s solution did not confirm induction of thyroid abnormalities.

• Pyruvic acid

Skin conditions that can be successfully treated with pyruvic acid include inflammatory acne, especially microcystic acne, ‘oily’ skin, moderate acne scars, warts, actinic keratosis, moderate photoaging (fine wrinkles, textural alterations, diffuse dyschromias, yellowing and mottling). Patients with photoaging can expect smoother skin texture, an improvement in fine wrinkles and an important reduction of hyperpigmented lesions (freckles and lentigines). Patients with acne and oily skin notice improvement of active acneic lesions and decreased seborrhoea. Pyruvic acid is our first choice in inflammatory acne and in macular acne scars. In our experience, this peeling agent is also the most effective peel in controlling rosacea.

While salicylic acid peels are our first choice in comedonal acne, we consider pyruvic acid peels as an alternative.

Actinic keratoses can be selectively treated with either TCA (30%) or pyruvic acid (50–60%). In melasma, pyruvic acid can be utilized in combination with 40% salicylic acid alone or with 30% salicylic acid + TCA 10% gel. Pyruvic acid peels can also be used in post-inflammatory hyperpigmentation and solar lentigines.

Side Effects, Complications and Alternative Approaches

Pyruvic acid causes very mild erythema and desquamation with minimal downtime. Pyruvic acid can be used in Fitzpatrick skin types I through IV.

Side effects include desquamation, crusting in areas of thinner skin, intense stinging and burning sensation during treatment. Since pyruvic acid has stinging and irritating vapors, using a handheld fan during the procedure can dissipate these fumes.

• Resorcinol

Conditions that can be successfully treated with resorcinol include acne scars, epidermal melasma, mild photoaging and freckles.

Although it is very effective for acne scars and melasma we limit its use due to the risk of toxicity and for the intense desquamation in the post peeling period.

Side Effects, Complications and Alternative Approaches

Side effects include postinflammatory hyperpigmentation. For this reason, we do not recommend usage of this agent in the summer as it may be a photosensitizer or in Fitzpatrick skin types of V or greater. Allergic or toxic reactions may also occur. Following a rescorcinol peel, the skin becomes brownish and tight on day 2 and undergoes crust separation starting on the third day. This desquamation is considered aesthetically unacceptable by most patients.

• Salicylic acid

Salicylic acid is a naturally occurring substance found in the bark of the willow tree. In concentrations of 3–5%, it acts as a keratolytic agent and enhances the penetration of other peeling agents. It is also a well-documented comedolytic agent. Salicylic acid is one of the oldest peeling agents with first documented use by Unna, a German dermatologist. Salicylic acid is a flexible substance that can be formulated in many types of vehicles. In our experience, salicylic acid is the best peeling agent for acne and macular acne scars (Figure 13.2), hyperpigmentation, melasma, and rosacea. Side effects are rare even in darker skin types.

Figure 13.2 30% salicylic acid, for few minutes, 5 session in 3 months. (A) Before the treatment. (B) After the treatment

We consider salicylic acid peels as first line therapy in the treatment of post inflammatory hyperpigmentation and melasma. We initially utilize 25% salicylic acid. If results are not satisfactory, 25% salicylic acid + 10% TCA gel can be used. In darker skin, 20–30 % salicylic acid is our first choice. Rosacea is another important indication for salicylic acid peels. In the telangiectatic phase, salicylic acid can be used in concentrations of 15–30%.

In solar lentigos, a combination of 30 % salicylic acid + TCA 25 % can be utilized even though we prefer 25% TCA alone as first choice. In mild to moderate photoaging, 20–30% salicylic acid alone or 25% salicylic acid + 25% TCA gel are our third and fourth choices.

Side Effects, Complications and Alternative Approaches

Side effects of salicylic acid peeling are mild and transient. Symptoms such as rapid breathing, tinnitus, hearing loss, dizziness, abdominal cramps, and central nervous system disturbance characterize salicylism, or salicylic acid toxicity. While true salicylism is rare in its occurrence, it has been reported with 20% salicylic acid application to 50% of the body surface, and with usage of 40 and 50% salicylic acid paste preparations. The authors have peeled more than 1,000 patients with the current 20 and 30% marketed ethanol formulations and had never observed cases of salicylism.

• Trichloroacetic acid

Trichloroacetic acid (TCA), first described by Roberts in 1926, is an inorganic compound, which is present in crystalline form. For the purposes of chemical peeling, it is mixed in an aqueous solution with distilled water to create the desired concentration. The use of TCA as a peeling agent has a wide variety of applications.

The most common indications we use TCA peels to treat are solar lentigos and severe acne scars (Figure 13.3). TCA can also be combined with salicylic acid for treatment of solar lentigos. For the treatment of recalcitrant hyperpigmentation and melasma, TCA can be combined with salicylic acid or glycolic acid.

Figure 13.3 35% TCA peel repeated at 15-day intervals for 3 sessions. The frosting gives the time of application. (A) Before the treatment. (B) After the treatment

We also utilize TCA in the treatment of xanthelasma. In mild to moderate photoaging, when 50–70% glycolic acid is ineffective, TCA 50% is the best choice for an all-over medium-depth peel. We tend to avoid the use of higher concentration TCA in darker skintypes. It is important to stress sun protection in all patients after treatment to avoid postpeel hyperpigmentation.

Side Effects, Complications and Alternative Approaches

It is of great importance to be familiar with the possible complications of TCA peels. These include infection, pigmentary changes, prolonged erythema, milia, acne, textural changes, and scarring. Scarring is a rare, yet feared complication of medium-depth chemical peels. Contributing factors include poor wound care, infection, uneven peeling depth, mechanical injury and previous recent history of ablative procedures. Localized areas of prolonged erythema, particularly on the angle of the jaw can be indicative of incipient scarring. Application of mild topical steroids to localized areas of erythema, proper wound care and infection prophylaxis can minimize the risk of scarring. If scarring is imminent, application of high-strength steroids, silicone gel and/or sheaths, and pulsed-dye lasers may be beneficial. Prolonged erythema may also be secondary to underlying rosacea, eczema, or use of retinoic acid. In this case, treatment with a mild topical steroid is usually effective. Milia formation is most likely due to over occlusion and can be minimized with the use of less occlusive emollients after reepithelialization. As noted previously, use of sunscreens, bleaching agents, and retinoic acid can minimize post peeling pigmentary complications.

Advanced Topics: Treatment Tips for Experienced Practitioners

In a recent study, we proposed an innovative method for the treatment of acne scars and chickenpox scars. If only a few isolated scars are present on a background on healthy skin, the best method is TCA CROSS (chemical reconstruction of skin scars). This method involves local serial applications of high concentration TCA (50% to skin scars with sharpened wooden applicators). The wooden end of cotton-tipped applicators can be sharpened to a dull point using number 10 blade to approximate the shape of the scar. No local anesthesia or sedation is needed to perform this technique. TCA is applied for a few seconds until white frosting is present in the scar. We then prescribe emollients for 7 days after, and high photoprotection. In our study, we repeated the procedure at 4-week intervals, and each patient received a total of three treatments. We opted to use a reduced concentration of TCA (50%) instead of 100% TCA which was first described in the study by Lee and colleagues. We demonstrated excellent cosmetic outcomes without significant adverse reactions. Of note, this precise technique can be used for focal chemical scar reconstruction without the prolonged downtime associated with classic full-face chemical resurfacing. Moreover, compared with other procedures, this technique can minimize or avoid the potential risks of scarring and dyspigmentation by sparing the adjacent normal skin and adnexal structures. The CROSS technique with 50% TCA is in our hands a very useful approach for the treatment of acne scars (Figure 13.4).

Figure 13.4 50% TCA repeated at 4-week intervals for 3 session treatment. The frosting gives the time of application.

Reproduced from Fabbrocini G, Cacciapuoti S, Fardella N et al 2008 CROSS technique: chimica reconstruction of skin scars method. Dermatologic Therapy, 21: S29–S32 (with permission)

Case Studies

• Case study 1: a patient with acne scars successfully treated with 30% TCA peeling

The patient had acne scars (Fig 13.5A). He had been previously treated with 30% salicylic acid and 50% glycolic acid peels without improvement. We decided to perform three 30% TCA peels at 4 week intervals. Photoprotection with SPF total block was recommended and alpha hydroxyacids were prescribed for topical application 4 times a week. The patient experienced good results after the second peeling with only mild transient erythema lasting 48 hours. Emollients were applied after each peeling. No burns or desquamation were observed until the third peeling. The results showed improvement of acne scars of about 70% and the patient was very satisfied with this course of therapy (Fig. 13.5B). Profilometry performed before and after treatments to evaluate reduction of roughness and deepness of the scars showed a reduction of about 65% in selected areas.