Introduction

Chemical peeling or chemoexfoliation, is the process in which the skin is wounded or burned with a chemical agent. The zone of cellular destruction and depth of the wound is dependent on several variables including the peeling agent, the concentration of the agent, skin thickness and skin permeability.¹ The immediate reaction of the skin is a second-degree, chemically induced burn. Inflammation begins shortly after the peel and extends variably into the epidermis and dermis. The inflam-matory response peaks at 48 hours but skin rejuvenation and collagen remodeling may last for weeks or months. Regeneration of the surface epithelium begins almost immediately and is usually complete by 5–14 days.

No matter which technique is utilized, if the wounding depth is significant there will be some permanent changes to the skin. The papillary dermal collagen changes from a wavy pattern to straight and parallel beneath the epidermal layer. The dermis shows fibroblastic proliferation and replacement of much of the old deformed elastic fibers with new elastic fibers.² Depending upon the degree of wounding and chemicals used, there may be fewer melanocytes both in the basal layer as well as in the dermis. This accounts for the lightening in color after peeling. This lightening, again, is a spectral change and may be permanent depending again upon the degree and agent of wounding. With fewer melanocytes the ability to tan is diminished accordingly. In terms of texture, the skin itself becomes smoother and more light reflective (shinier) which is generally a healthy replacement for the previously sun-damaged skin (Fig. 21-1). The potential increased sun sensitivity due to decreased melanocytes makes sun protective measures very important.

In general, the deeper the wound, the deeper the zone of replacement of old, damaged, and disorganized skin structural elements with new, healthy, and well-organized elements.³ By the same token, the deeper the wound, the greater the potential for scarring and pigment changes. Chemical peels may be divided into three types, graded by the depth of the wound (Table 21-1). Superficial-depth wounding is to the stratum granulosum, papillary dermis. Medium-depth wounding is to the upper reticular dermis. Deep-depth wounding is to the mid-reticular dermis.

Indications and patient selection

Chemical peeling is indicated in any patient whose skin may benefit from greater elasticity, increased smoothness, removal of fine wrinkles, softening or obliteration of deep creases and lessening of pigmentary irregularities. Chemical peeling replaces the sallow, aged appearance of sun-damaged skin with a healthy and youthful glow. Thus, virtually all patients requesting blepharoplasty or any other facial cosmetic procedures have indications for chemical peeling.

Chemical peeling is often performed in conjunction with blepharoplasty, endoscopic brow lifting and facelifting. In general, skin that has been surgically undermined is not peeled at the same time as surgery. If the depth of surgical dissection is subcutaneous, it is possible that superficial damage to the skin from the chemical peel may result in full thickness skin necrosis. However, if the depth of dissection preserves the subdermal vasculature, as in subperiosteal facelifting or transconjunctival blepharoplasty procedures, simultaneous peeling is considered safe.

Simultaneous transconjunctival blepharoplasty and chemical peeling has been performed since 1989.⁴ The primary aim of lower blepharoplasty is either the removal or repositioning of fat in order to address the undesirable convexity (bulging) of the lower eyelid and/or central midface concavity. Approximately 70 percent of patients who want to undergo lower blepharoplasty have such a small component of excess skin that the risk of the transcutaneous approach outweighs the advantage of removing a few millimeters of vertical skin, particularly when the skin problem is mostly due to actinic damage. The authors have been performing only transconjunctival blepharoplasty approaches on these patients for the past 20 years.

One of the authors (DMM) developed and has refined the technique of simultaneous transconjunctival blepharoplasty and chemical skin peeling since 1989.⁴ We now all routinely use this combination procedure (Fig. 21-2). The 70 percent of patients in whom skin removal has too great a potential risk will all potentially benefit from simultaneous transconjunctival blepharoplasty and chemical peel rejuvenation of the skin of the lower eyelids; in fact, many of the 30 percent in whom the risk of blepharoplasty is acceptable can also significantly benefit from this simultaneous blepharoplasty and chemical peel without the risk of an infralash incision.

Figure 21-2 (Surgeon: JAH) A 67-year-old woman before (A) and after (B) upper blepharoplasty, lower transconjunctival blepharoplasty, and simultaneous eyelid chemical peel and facial laser resurfacing. An improvement in skin texture is evident.

Chemical peeling is also performed in conjunction with facelifting procedures. In general, lower facelifting procedures will improve the jowls and tighten the neck. It does little to improve the perioral rhytids, general loss of skin elasticity and dyschromia. Upper facelifting procedures (forehead lifts) will elevate the brows and reduce dynamic wrinkles. It will, however, not delete the permanent creases that are often found in the glabella and forehead regions. Depending on the degree and depth of these wrinkles, a variety of chemical peels can safely be performed simultaneously in areas that have not been surgically undermined. Thus, it is common for us to simultaneously perform an upper and lower facelift, transconjunctival blepharoplasty along with perioral, forehead and lower eyelid chemical peeling.

Evaluating the skin⁵

Hypopigmentation after chemical peel is a concern. Certainly, the issue of skin color change must be thoroughly discussed with the patient preoperatively. The deeper the wounding the more potential for hypopigmentation. In addition, as a chemical, phenol is melanotoxic. Originally it was thought that permanent hypopigmentation presented little or no problem for light-skinned patients (Fitzpatrick’s classifications I–II⁶) (Table 21-2). We have come to realize that these very light skinned patients will have significant whitening of their skin, especially after deep peels. If a full-faced peel is performed and the edges of the peeling are feathered onto the neck, the hypopigmentation can be easily camouflaged. If, however, individual regions are only peeled, the color contrast between the peeled and non-peeled zones can be quite noticeable. This will force the patient to require a base or foundation make-up to blend the peeled and non-peeled regions.

Table 21-2 Reaction to sun by skin pigment type

Moderately dark patients (Fitzpatrick II–III) have less of an issue with permanent hypopigmentation. These patients often develop splotchy post-inflammatory hyperpigmentation during the first 3 months after a moderate to deep peel. The hyperpigmentation is usually temporary and easily controlled with bleaching agents. Peeling in darker skinned patients (Fitzpatrick’s classification IV–VI) can be fraught with significant pigmentation issues. Postoperatively, these patients may develop areas of hyperpigmentation and hypo-pigmentation, which cannot be readily camouflaged with make-up.

Contraindications

There are few absolute contraindications to chemical peeling. Three groups of patients must be considered cautiously as candidates. First are those with olive or darkly pigmented skin. The peel may permanently remove too much pigment or may result in a blotchy or hyperpigmented appearance. The second group is composed of patients whose skin is fair but has been frequently sun-exposed for many years. These patients now have permanently pigmented skin, and chemical peeling may result in an obvious demarcation between the treated area and the untreated area, even if careful feathering is performed. The third group is made up of the fair skinned and freckled. These patients risk an odd appearance if they lose all their facial freckles in one area while retaining freckles in adjacent areas.

Chemexfoliation and wounding agents

Chemical peeling is a commonly performed procedure. The depth (and, therefore, effectiveness) varies with the chemical agent used, its concentration, and the conditions under which it is applied. The wide spectrum of agents and formulas for peeling includes retinoic acid (Retin-A), solid carbon dioxide, sulfur solutions, resorcinol, salicylic acid, alpha-hydroxy acids, trichloroacetic acid (TCA), and phenol and phenol formulas. Table 21-1 lists the most common peeling agents, concentrations, and formulations and the depth to which they can wound.

The surgeon must determine the depth to which he or she wishes to wound the skin, since it is wound depth that determines the potential for the final result. Unfortunately, depth is not simplistically determined by chemical formulas and concentrations, as implied in Table 21-1. Other major factors that help determine wound depth are skin type (Fitzpatrick’s skin classifications I–VI), skin condition and thickness, pretreatment with retinoic acid (Retin-A), alpha-hydroxy acids, alpha-keto acids, low dose cis-retinoic acid, epidermabrasive exfoliants, and defatting preparations. These agents alter the permeability of the skin to the wounding agent. Furthermore, the larger the amount of agent applied, the longer and harder the agent is rubbed onto the skin, and the longer the duration of contact between agent and skin, the deeper the wounding caused by the same agent. Finally, applying tape over the agent (occlusion) drives the chemical deeper into the skin.

Each of the several chemical wounding agents (see Table 21-1) may be used in various strengths. The most common agents, in increasing order of strength, are TCA (15, 20, 25, 35%) and phenol 89 percent. Most wounding agents can be driven deeper into the skin, and thus cause a deeper burn, by occlusion (taping or ointments), wetter applications, multiple applications, or vigorous scrubbing of the agent into the skin. Due to the increased risk of scarring due to uneven penetration, the authors do not use taping as a method of penetration enhancement. Thus, we will not discuss taping in this chapter.

The 15 percent and 20 percent dilutions of TCA are used as ‘freshening peels’ and in a single application have a minimal potential for complications and only provide minimal long term improvement. We suggest to participants in our teaching courses that they begin their experience in chemical peeling with these 15–20 percent TCA freshening peels independent of or in conjunction with lower transconjunctival blepharoplasty. Compared to blepharoplasty alone, patient healing time is only minimally increased. Usually the skin is fully re-epithelialized, such that the patient can return to comfortably meeting the public and wearing make-up (or not needing make-up), within 7–10 days – at which time there are still usually telltale signs of surgery after a blepharoplasty anyway.

After a great deal of experience has been achieved, we find our most commonly used agent is TCA 35 percent for combined simultaneous transconjunctival blepharoplasty and chemical peeling. In our experience, this concentration produces satisfactory results with one application in most patients, assuming that the patient selection, application of the chemical, and aftercare are appropriately carried out. There is still some minimal risk of scarring, textural change, eyelid contracture, or undesirable pigmentary changes. On occasion, and for selected patients, we use phenol 89 percent or Baker’s phenol mixture combined with transconjunctival blepharoplasty. However, these agents are not for the novice. They carry much more risk of complications.

Routinely for eyelid skin peeling, other than in conjunction with blepharoplasty, we often use the phenol preparations. Phenol wounds more deeply than trichloroacetic acid and as such is very effective in treating deeper rhytids and creases in the eyelids.

It is thought, though still not conclusively proven, that phenol’s ability to wound increases with the dilution. (That is to say, the more dilute the phenol preparation, the greater the penetration.) Phenol preparations such as Baker-Gordon formula (Table 21-3) dilute the phenol and use additional ingredients. Studies have shown that the most toxic phenol preparation is a phenol and water combination of 2 : 1. Thus, any dilution of full-strength phenol preparation, as occurs when tears run onto the eyelid, may increase the depth of penetration.

Table 21-3 Baker-Gordon chemical peel formula

In choosing the chemical agent, the surgeon must keep in mind differences in wounding agents, the preparation of the skin as well as the anatomic variations in the skin of each area of the face. For example, one may apply Baker-Gordon formula laterally, to the crow’s feet and in the deep rhytids of the glabella and perioral region; 35 percent TCA to the forehead and infrabrow area; 25 percent TCA inferiorly to the upper blepharoplasty incision line, on the medial canthus, and over the bridge of the nose at the radix; and continue with 25 or 35 percent TCA from the lower eyelid lash line inferiorly over the remainder of the face. The solutions should be applied in a feathered fashion to provide a natural look without a demarcation line. It is imperative that the solutions are not applied inferior to the jawline for this may result in scarring.