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Light Chemical Peels
Introduction
Chemical peels are classified by their level of injury to the skin as very light/very superficial, light/superficial, medium-depth, or deep peels. They can also be classified by their mechanism of action as caustic, metabolic, or toxic peels. They induce a controlled destruction of parts or the whole epidermis with or without the dermis, producing exfoliation with ablation of superficial lesions. The ablation is followed by regeneration of new epidermal and dermal tissue.
Very light or very superficial peels ( Table 4.1 ) are those that lead to a necrosis of the epidermis at the level of the stratum corneum. In contrast, light peels or superficial peels are those that penetrate through the epidermis and lead to necrosis of the entire epidermis down to the level of the stratum granulosum or the basal lamina. Light peels cause reduced corneocyte adhesion and increase the collagen formation in the dermis. In this way they improve the skin’s radiance and luminosity.
TABLE 4.1
Agents for Very Light Peels
Data from Drake LA, Dinehart SM, Goltz RW et al 1995 Guidelines of care for chemical peeling. Guidelines/Outcomes Committee: American Academy of Dermatology. Journal of the American Academy of Dermatology 33:497–503; Khunger N 2008 Standard guidelines of care for chemical peels. Indian Journal of Dermatology, Venereology and Leprology 74 Suppl:S5-12; Clark E, Scerri L 2008 Superficial and medium-depth chemical peels. Clinical Dermatology 26:209–218; and Committee for Guidelines of Care for Chemical Peeling. Guidelines for chemical peeling in Japan (3rd edition). Journal of Dermatology. 2012;39(4):321–325.
| Peeling Agent | Concentration | Procedure |
|---|---|---|
| Trichloroacetic acid (TCA) | 10% | Applied in 1 coat |
| Glycolic acid (GA) | 20%–50% | Applied briefly for 1–4 minutes |
| Salicylic acid | 10%–30% | 4–6 minutes |
| Resorcinol | 20%–30% | Applied briefly for 5–10 minutes |
| Jessner’s solution | Salicylic acid 14 g, lactic acid (85%) 14 g, resorcinol 14 g with ethanol to make 100 mL | Applied in 1–3 coats |
| Retinoic acid | 1%–5% | Washed off after 4–5 hours |
Light peels are used to treat pigmentary disturbances like solar lentigines, melasma and hyperpigmentation, papulopustular rosacea, superficial acne scars and photoaged or light-damaged skin, as well as to improve skin tone.
The type of chemical peel and depth of the peel is selected according to the severity of the wrinkling, laxity, and the patient’s downtime expectations. To enhance cosmetic improvement, topical skin-rejuvenating creams and dermal fillers can be used. Light peels should be repeated to achieve the best possible cosmetic improvement and to obviate recurrence of the skin lesions being addressed.
Schürer and Wiest divide the penetration depths more exactly into five levels ( Fig. 4.1 ): very superficial peels only reach the stratum corneum (level A), and superficial/light peels reach the middle epidermal layers (level B) ( Table 4.2 ). A deeper light peel to a medium-depth peel reaches just below the stratum basale (level C) and in this way causes epidermolysis.
TABLE 4.2
Agents for Light Peels
| Peeling Agent | Concentration | Procedure |
|---|---|---|
| Trichloroacetic acid (TCA) | 10%–30% | Applied in 1 coat |
| Glycolic acid (GA) | 20%–70% | Applied for a variable time (2–20 minutes) |
| Salicylic acid | 10%–30% | Applied in 1 coat and left on for 5–6 minutes |
| Mandelic acid | 20%–25% | — |
| Pyruvic acid | 40%–60% | Application until erythema occurs, 2–4 minutes |
| Jessner’s solution | Salicylic acid 14 g, lactic acid (85%) 14 g, resorcinol 14 g with ethanol to make 100 mL | Applied in 4–10 coats |
| Resorcinol | 40%–50% | Applied for 30–60 minutes |
Very superficial peels can be repeated every 1 to 2 weeks, and light peels can be repeated every 2 to 4 weeks. Peeling too frequently can result in an increased risk for complications, in particular persistent erythema, postinflammatory hyperpigmentation, infections, and scarring. Because of the simplicity, low morbidity, cost effectiveness and simple availability of solutions, chemical peels still play an important role in treating photoaging and pigmentary disturbances, even though there are more modern techniques available such as lasers.
Peeling Agents: Chemistry and Chemical Formulations
Alpha-Hydroxy Acids
Alpha-hydroxy acids (AHAs) are a group of organic acids. They are often referred to as fruit acids, including glycolic acid from cane sugar, citric acid from citrus fruits, and malic acid from apples. The AHAs used for a chemical peeling are produced in chemical laboratories. Additional AHAs also include lactic and mandelic acid. Lactic acid decreases corneocyte cohesion, leading to a thinner stratum corneum. It moisturizes and brightens the skin and improves superficial acne scarring by improving the skin texture and appearance of the scars. Mandelic acid has slow skin penetration due to its large molecule size. Therefore, it is considered a safe, light peeling agent. In concentrations of 20% to 50% it has a skin-rejuvenation and lightening effect.
AHAs are considered keratolytic agents because they cause a superficial exfoliation by breaking bonds between keratinocytes in the different layers of the stratum corneum and stratum granulosum. AHAs help to correct an abnormally thickened stratum corneum of the epidermis. This effect lasts for up to 14 days after the end of the therapy. The daily use of topical AHA lotion leads to an increased epidermal thickness. In addition, AHAs lead to an increased dermal thickness by stimulating an increased deposition of collagen and glycosaminoglycans. AHAs are particularly suitable for treating patients with very sensitive skin, a ruddy complexion, telangiectasias, or moderate sun damage.
Beta-Hydroxy Acid
Both salicylic acid (SA) and beta-lipohydroxy acid (LHA), which is a derivative of SA, have antibacterial, antiinflammatory, antifungal, and anticomedogenic properties. Due to the additional fatty chain, LHA is more lipophilic than SA and has a more targeted mechanisms of action and a greater keratolytic and comedolytic effect. LHA penetrates well into the sebaceous follicle and through the epidermis, but less deeply into the skin compared with glycolic acids and SA. It is particularly effective in the superficial layers of the stratum corneum, specifically the stratum compactum/disjunctum interface, and focuses its effects on the follicle and epidermis. Neutralization is neither necessary nor possible when peeling with LHAs.
Retinoic Acid
Retinoic acids (RAs) (all- trans retinal and retinoic acid) are usually used alone or in combination with AHAs or other ingredients. RAs lead to a thinner and more compact stratum corneum and a thicker epidermis. They can help to improve dyschromias by creating a more consistent distribution of melanin throughout the epidermis. Furthermore, RAs reverse the number of atypical keratinocytes, thus leading to an improvement or eradication of actinic keratosis. By increasing production of collagen and capillary branching in the dermis, RAs improve skin texture and superficial dyschromias and lead to a pinker, rosier complexion. The side effects of RAs include increased photosensitivity. Exposure to sunlight during treatment should therefore be strictly avoided.
AHAs act mainly on the stratum granulosum, compared with RAs, which mainly act on the stratum corneum. Both AHAs and RAs lead to an increased and accelerated skin turnover from the normal 28 days to 10 to 12 days. RAs and glycolic acids facilitate the distribution of melanin throughout the epidermis. This skin-lightening effect can be used for the treatment or reduction in the incidence of postinflammatory hyperpigmentation ( Fig. 4.2 ).
In addition to the peels, topical products with a lightening effect such as hydroquinone, Kojic acid, or tyrosinase inhibitors can be used. They inhibit tyrosinase, thus blocking the conversion of tyrosine into L-dopa. This may reduce the melanin production of the skin and result in a lower risk of hyperpigmentation. Supplementary treatment with skin-lightening products should be started 2 to 4 weeks before the chemical peel, be continued during the peel, and not be finished until 2 to 3 months after cessation of the peels. The more pronounced the hyperpigmentation and the darker the pigment, the earlier the preconditioning should be started (see Chapter 3 ).
Salicylic-Mandelic Combination Acid Peels
Salicylic-mandelic combination acid peels, in concentrations of 20% SA and 10% mandelic acid, are effective in treating acne vulgaris and acne scars. One study by Sarkar et al. showed that salicylic-mandelic combination acid peels are better tolerated and therefore more suitable in treating Indian patients with melasma compared with glycolic acid peels (35%).
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