Over the last 30 years, the science of chemical peeling has evolved dramatically, improving our understanding of the role of peeling ingredients and their potential to treat acne and acne scarring.
Superficial peels which produce injury limited to the epidermis are effective for mild to moderate acne, says a review of the use of peels by the International Peeling Society (IPS) in the Journal of the American Academy of Dermatology.1 In darker skin types, superficial peels are safe and effective in reducing papule, pustule, and comedone count.
Medium depth peels which produce injury into or through the papillary dermis can be used to treat acne scarring. “Careful patient and peel selection will ensure procedural success with excellent results,” says Kachiu Lee, a dermatologist in Providence, RI and one of the authors of the review.
Novice peelers should start with superficial peels on Fitzpatrick Skin types I and II so that they can get used to the acids, applicator types and techniques with minimal risk of adverse side effects, she advised. “The difference between satisfactory versus excellent results depends on the selection of the proper peeling agents and the understanding of gentle versus aggressive application technique during their use.”
Common superficial peels include glycolic acid, salicylic acid, Jessner’s solution, retinoic acid, lactic acid, mandelic acid, pyruvic acid and trichloroacetic acid (TCA) 10-35%. Of these, only glycolic and pyruvic acid peels require neutralization, either by sodium bicarbonate or by removal with water. Superficial peels may be grouped into alpha and beta-hydroxy acids. Alpha-hydroxy acids, such as glycolic acid, are water soluble. Beta-hydroxy acids, such as salicylic acid, are lipid soluble.
Salicylic acid (SA) is a beta-hydroxy acid and a phenolic compound with anti-inflammatory, antimicrobial, and depigmenting properties, and is safe in all Fitzpatrick phototypes. It is particularly effective for comedonal acne because of its lipophilic and comedolytic effect.2
When SA 20%-30% is in an ethanol (hydroalcoholic vehicle [HA]) some patients develop SA-HA ‘hot spots,’ or areas of over-penetration, that may result in post-inflammatory hyperpigmentation (PIH), so a polyethylene glycol (PEG) vehicle was developed that slows delivery, while simultaneously increasing follicular penetration. A split-face study found that 30% SA-PEG was superior to 30% SA-HA,3 which yields mild desquamation after two days.
Glycolic acid (GA) is a water-soluble, alpha-hydroxy acid, and pyruvic acid (PA) is an alpha-keto acid. To avoid over penetration, GA and PA must be neutralized as soon as the clinical endpoint of erythema is reached, or after 5 minutes if no erythema is present. Sometimes erythema quickly progresses to frosting and this rapid transition is associated with scar or PIH, and, consequently, there has been a shift towards safer alternatives, such as SA, MJS, or low-strength GA.
Trichloroacetic acid (TCA) is highly water soluble, with no crystallization in up to 90% TCA solution. Depth of penetration correlates directly to concentration and TCA over 35% is used for focal treatment of individual lesions, since pigmentary complications and scars are common with use over large areas. TCA >80% is only appropriate for focal use, such as chemical reconstruction of skin scars (CROSS); it increases collagen deposition and decreases scar depth of focal ice pick or boxcar acne scars.
All-trans retinoic acid or tretinoin peels cause minimal discomfort during application because of their nearly neutral pH and intranuclear action. “Tretinoin peels at varying concentrations may be used to treat acne, although supportive clinical trial data is sparse,” Lee says.
Jessner’s solution consists of 14% resorcinol, 14% salicylic acid and 14% lactic acid (LA) in 95% ethanol. Resorcinol may cause contact allergy, and risks inducing cross-sensitivity with hydroquinone, with repeated exposure so modified Jessner’s solution (MJS) was created by increasing the concentration of SA and LA to 17% and replacing resorcinol with 8% citric acid.
Medium depth peels
Historically, medium depth peels were performed using TCA 50%, which resulted in uneven penetration and erosions, PIH and scars. Safer medium depth peels have been developed and include 70% glycolic acid+35% TCA (Coleman peel), Jessner’s solution (JS)+35% TCA (Monheit peel), solid C02+35% TCA (Brody peel).
Medium depth chemical peels using solid C02 slush with focal 50% TCA to efface scar rims6 or JS followed by 35% TCA may improve acne scars in lighter skin types. Focal dermabrasion may follow the peel.7
Solid C02 slush is created by dipping hand-held blocks of solid C02 (-78.5°C) in a 3:1 acetone to alcohol solution and allowing it to glide smoothly over the skin, which has been degreased with acetone, for 3 to 15 seconds until there is transient white frost with residual erythema. TCA is then applied until even light white or solid white frost is achieved, which corresponds to epidermal and dermal protein denaturation.
The Monheit peel uses JS instead as a keratolytic agent to further TCA penetration, and is performed by degreasing the face with acetone and then applying JS until a reticulate frost is obtained. MJS can be used in darker skin to treat pigmentation and has less risk of contact sensitivity.
With the Coleman peel degreasing with acetone is unnecessary if patients are not wearing make-up or other products. GA 70% is first applied for approximately 2 minutes until erythema develops, then neutralized before TCA 35% is applied.
Solid C02+ TCA is histologically the deepest medium depth peel and easier for the patient to tolerate than JS or GA followed by TCA. Analgesia is unnecessary for any medium depth peel if the operator is experienced in performing the peel rapidly and smoothly, Lee says.
Preparation and aftercare
Medium depth peels are not recommended for phototypes ≥IV due to the risk of post-inflammatory hyperpigmentation, but this risk may be reduced by pre-peel preparation with hydroquinone for 1 month and peeling during the winter season.
For superficial and medium peels, pre-treatment with topical tretinoin for 2-4 weeks enables a more uniform frosting and improves healing time. It is recommended that tretinoin is stopped one week prior to the peel in skin types IV-VI to prevent overpenetration and PIH. Pretreatment for 2 weeks with hydroquinone 2% is associated with less PIH.
Post-peel management focuses on expediting healing and preventing infection. Icepacks can be used for edema and mild discomfort, and gently soaking and cleansing the skin and applying white petrolatum promotes re-epithelialization. Patients with a history of herpes simplex virus should receive medical prophylaxis.
Sun protection is vital before and after the peel. Physical barriers should be used until re-epithelialization, then a physical sunscreen can be applied.
1 Lee KC, Wambier CG, Soon SL, Sterling JB, Landau M, Rullan P, Brody HJ, on behalf of the International Peeling Society(IPS), Basic chemical peeling—superficial and medium depth peels, Journal of the American Academy of Dermatology (2019), doi: https://doi.org/10.1016/j.jaad.2018.10.079
2 Dainichi T, Ueda S, Imayama S, Furue M. Excellent clinical results with a new preparation for chemical peeling in acne: 30% salicylic acid in polyethylene glycol vehicle. Dermatol Surg. 2008;34(7):891-899.
3 Dainichi T, Ueda S, Imayama S, Furue M. Excellent clinical results with a new preparation for chemical peeling in acne: 30% salicylic acid in polyethylene glycol vehicle. Dermatologic Surg. 2008;34(7):891-899.
4 Kessler E, Flanagan K, Chia C, Rogers C, Glaser DA. Comparison of alpha- and beta555 hydroxy acid chemical peels in the treatment of mild to moderately severe facial acne vulgaris. Dermatol Surg. 2008;34(1):45-50.
5 Garg VK, Sinha S, Sarkar R. Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study. Dermatol Surg. 2009;35(1):59-65.
6 Brody HJ, Hailey CW. Medium-depth chemical peeling of the skin: a variation of superficial chemosurgery. J Dermatol Surg Oncol. 1986;12(12):1268-1275.
7 Al-Waiz MM, Al-Sharqi AI. Medium-depth chemical peels in the treatment of acne scars in dark-skinned individuals. Dermatol Surg. 2002;28(5):383-387.