Scientific Background

Chemical resurfacing has a long and well-documented history [1]. Since the late 1800s, physicians have been experimenting with various procedures and techniques involving both chemical and mechanical skin resurfacing. Chemical resurfacing procedures involve the application of a caustic chemical agent to the skin, which produces a controlled, partialthickness injury, thereby promoting the growth of new skin with improved surface characteristics. Chemical peeling is intended to produce a controlled partial-thickness injury to the skin, destroying varying amounts of epidermis and upper portions of the dermis.A wound-healing response following the injury involves (depending on the depth of injury) (1) removal of actinic keratoses (AK) and lentigines, (2) epidermal regeneration by epithelial migration from adnexal structures, (3) decrease in solar elastosis, and (4) replacement of new dermal connective tissue [4].

Chemical peels are categorized into superficial, medium-depth, and deep types of wounding (Table 4.1). In this section, the focus will be on superficial peels with a target depth penetration from the stratum corneum through to the superficial papillary dermis (0.06 mm). Superficial chemical peels are divided into two subgroups: very light and light. Examples of very light superficial chemical peels include low-potency concentrations (20–60%) of glycolic acid, alpha-hydroxy acids, 10–20% TCA, tretinoin, Jessner’s solution, and salicylic acid. With very light peels, the level of injury is generally limited to the stratum corneum, which creates exfoliation without clinical vesiculation but may also penetrate into the stratum granulosum. With light superficial chemical peels, such as 70% glycolic acid,25–30% TCA,and solid carbon dioxide (CO₂) slush, the injury is to the entire epidermis extending down to the basal cell layer or upper papillary dermis, stimulating the regeneration of a new epithelium.

Table 4.1. Chemical peel classifications   Chemical peeling agents Depth of penetration   Glycolic acid 20–50% Salicylic acid 20–30% Resorcinol 20–30% (5–10 min) Jessner’s Solution (1–3 coats) Trichloroacetic acid 10% (1 coat) Microdermabrasion (2 passes) Very superficial/stratum corneum exfoliation   Glycolic acid 50–70% (5–20 min) Jessner’s solution (5–10 coats) Resorcinol 50% (30–60 min) Trichloroacetic acid 10–35% (1 coat) Superficial/epidermal necrosis   Phenol 88% Glycolic Acid 70% (5–30 min) Trichloroacetic acid 35% in combination with: Glycolic acid (50–70%) Solid CO2 Jessner’s solution Medium-depth/papillary dermal necrosis   Pyruvic acid 40–70% Modified Baker’s peel (2 drops croton oil) Baker-Gordon phenol peel Deep/reticular dermal necrosis