CHAPTER 50
Medium‐Depth Chemical Peels

Gary D. Monheit and Katherine T. Hrynewycz

Total Skin & Beauty Dermatology Center, PC, and Departments of Dermatology and Ophthalmology, University of Alabama, Birmingham, AL, USA

Introduction

A number of acidic and basic chemical agents have been used to produce the varying effects of light, medium, or deep chemical peels, mediated by differences in their ability to penetrate and damage epidermal and dermal skin components. The level of penetration, destruction, and inflammation determines the degree of skin rejuvenation. The stimulation of epidermal growth through the removal of the stratum corneum without necrosis characterizes light superficial peels. Through exfoliation, it thickens the epidermis with qualitative regenerative changes. Destruction of the epidermis defines a full superficial chemical peel inducing the regeneration of the epidermis. Further destruction of the epidermis and induction of inflammation within the papillary and upper portions of the reticular dermis constitutes a medium depth peel. Further inflammatory response in the mid‐reticular dermis induces new collagen production and ground substances constituting a deep chemical peel [1].

Formulations

Trichloracetic acid

Trichloracetic acid (TCA) has become the gold standard of chemical peeling agents, based on its long history of usage, versatility in peeling, and chemical stability. The first documented use for skin rejuvenation dates back as far as 1882, when German dermatologist Paul Gerson Unna described the properties of salicylic acid, resorcinol, phenol, and TCA [1]. TCA has since been used in many concentrations because it has no systemic toxicity and can be used to create superficial, medium, or even deep wounds in the skin. TCA is naturally found in crystalline form and is mixed weight‐by‐volume with distilled water. It is not light sensitive, does not need refrigeration, and is stable on the shelf for over 6 months. The standard concentrations of TCA should be mixed weight‐by‐volume to assess the concentration accurately. TCA crystals weighing 30 g are mixed with 100 mL distilled water to give an accurate 30% weight‐by‐volume concentration. All other dilutional system – volume dilutions and weight‐by‐weight – are inaccurate in that they do not reflect the accepted weight‐by‐volume measurements cited in the literature.

Because TCA, at concentrations of 50% or above, has a high potential to be scarring, the use of higher concentrations has fallen out of favor [2]. Thus, it is not used as a deep peel because of the incidence of scarring at high concentrations. Therefore, combined applications using an initial modifying treatment followed by a 35% TCA formula were developed to better control the level of damage and minimize the risk of side effects [3].

Brody [4] first developed the use of solid CO₂ applied with acetone to the skin as a freezing technique prior to the application of 35% TCA. The preliminary freezing appears to break the epidermal barrier for a more even and complete penetration of the 35% TCA. Monheit [5] then introduced the use of Jessner’s solution prior to the application of 35% TCA (Table 50.1). The Jessner’s solution was found to be very effective in destroying the epidermal barrier by breaking apart individual epidermal cells. This also allows a deeper penetration of the 35% TCA and a more even application of the peel solution. Similarly, Coleman and Futrell [6] have demonstrated the use of 70% glycolic acid prior to the application of 35% TCA. Its effect has been very similar to that of Jessner’s solution.

Table 50.1 Jessner’s solution (Combes’ formula).

Resorcinol	14 g
Salicylic acid	14 g
85% Lactic acid	14 g
95% Ethanol (q.s.ad.)	100 mL

q.s.ad, a sufficient quantity up to.

Table 50.2 Agents used for medium‐depth chemical peeling.

Agent	Comment
40–50% TCA	Not recommended
Combination 35% TCA + solid CO₂ (Brody)	The most potent combination
Combination 35% TCA + Jessner’s solution (Monheit)	The most popular combination
Combination 35% TCA + 70% glycolic acid (Coleman)	An effective combination
88% phenol	Rarely used

All three combinations have proven to be as effective as the use of 50% TCA; however, with a greater safety margin. The application of acid and resultant frosting are better controlled with the combination so that the “hot spots” with higher concentrations of TCA can be controlled, creating an even peel with less incidence of dyschromias and scarring (Table 50.2).

In the face of resorcinol sensitivity, modified Jessner’s solution (MJS) may be used. This solution uses 8% citric acid in place of resorcinol, while salicylic acid and lactic acid are each increased to 17% [7]. However, there is inadequate data to equate the efficacy of Jessner’s solution with MJS.

Advantages and disadvantages

The advantages of chemical peeling compared with other modalities used to treat photoaging or precancerous lesions include the low cost, the ease of a single application, and reliable efficacy. Additionally, chemical peeling may be performed in any office setting with routine dermatologic supplies such as 2 × 2 or 4 × 4 inch gauze pads and cotton‐tipped applicators, and does not require special equipment (Figure 50.1). When performed properly on the correctly chosen patient, a medium depth peel will reliably improve the appearance of photoaged skin and produce sustained clearing of most precancerous skin lesions for a period of several months to several years [8].

Schematic illustration of standard setup for Jessner’s and trichloracetic acid (TCA) combination peel. The standard setup includes a facial cleanser such as Septisol, acetone, Jessner’s solution, 35% TCA, cotton-tipped applicators, 2 × 2 inch and 4 × 4 inch gauze pads, and cool-water soaks for patient comfort. — **Figure 50.1** Standard setup for Jessner’s and trichloracetic acid (TCA) combination peel. The standard setup includes a facial cleanser such as Septisol, acetone, Jessner’s solution, 35% TCA, cotton‐tipped applicators, 2 × 2 inch and 4 × 4 inch gauze pads, and cool‐water soaks for patient comfort.

Indications

While superficial peels may improve conditions such as acne and skin texture, and deep peels may help improve moderate rhytides and acne scarring, current indications for medium‐depth chemical peeling include Glogau type II photoaging (Table 50.3), epidermal lesions such as actinic keratoses, pigmentary dyschromias, mild acne scarring, as well as full face blending the effect of deeper resurfacing procedures in selective cosmetic areas (Table 50.4) [9].

Table 50.3 Glogau’s classification of photoaging.

Group	Severity	Age group (years)	Features
I	Mild	Usually 28–35	Mild pigmentary change
			No keratoses
			Minimal wrinkles
II	Moderate	Usually 36–50	Early senile lentigines
			Keratoses palpable but not visible
			Parallel smile lines beginning
III	Advanced	Usually 51–65	Obvious dyschromia, telangiectasias
			Visible keratoses
			Wrinkles even when not moving facial muscles
IV	Severe	Usually 66–75	Yellow‐gray color of skin
			Prior skin malignancies
			Wrinkled throughout with no normal skin

Table 50.4 Major indications for medium‐depth chemical peels.

Destruction of premalignant epidermal lesions – actinic keratoses

Resurfacing moderate to advanced photoaged skin (Glogau Levels I, II)

Improving pigmentary dyschromias

Improving mild acne scars

Blending laser, dermabrasion, or deep chemical peeling in photoaged skin (transition from treated to non‐treated area)

The Jessner’s + 35% TCA peel is particularly useful for the improvement of mild to moderate photoaging. It freshens sallow, atrophic skin and softens fine rhytides, with minimal risk of textural or pigmentary complications. Deep furrows, however, are not eliminated with this peel and there is no significant skin retraction as is seen with ablative fractional laser resurfacing. When used in conjunction with a pre‐treatment program of retinoid, bleaching agent and sunscreens, a single Jessner’s + 35% TCA peel lessens pigmentary dyschromias and lentigines as well as, or even more effectively, than repetitive superficial peels. Epidermal growths such as actinic keratosis also respond well to this peel. In fact, the Jessner’s + 35% TCA peel has been found to be as effective as topical 5‐fluorouracil chemotherapy in removing both grossly visible and clinically undetectable actinic keratosis, but has the advantages of lower morbidity and greater improvement in associated photoaging [8].

Another indication for the Jessner’s + 35% TCA peel is to blend the effects of other resurfacing procedures with the surrounding skin. It is important to note that when used in combination with other resurfacing procedures such as laser ablation and dermabrasion, the peel should be performed first, in order to avoid accidental application of the peeling agent onto previously abraded areas of skin which may lead to scarring [10].

Contraindications

Several contraindications exist when choosing a medium‐depth chemical peel (Table 50.5). Because patient compliance during the recovery period is essential to avoiding permanent negative sequelae, a medium depth peel should not occur in the setting of a poor physician–patient relationship. A frank discussion of what the peel can and cannot accomplish is necessary, and unrealistic expectations on the part of the patient must be recognized. Poor general health and nutritional status will compromise wound healing and should dissuade a procedural approach. A 2017 consensus article by the American Society for Dermatologic Surgery concluded that superficial chemical peels can be performed safely during or immediately after isotretinoin use. However, there is insufficient data to support the use of medium depth peels during isotretinoin therapy [11]. Moreover, isotretinoin therapy within the previous 6 months has been associated with increased risk of scarring, and a medium‐depth chemical peel should be delayed until the patient is beyond 6 months of finishing a course of isotretinoin. Active infections or open wounds such as herpes simplex vesicles, excoriations, or open acne cysts should postpone the treatment until such conditions resolve. All patients with a history of herpes simplex virus (HSV) I of the facial area should be premedicated with an antiviral agent such as acyclovir or valacyclovir and remain on prophylactic therapy for 10 days.