Superficial Peel
AHA (α-hydroxy acid) and BHA (β-hydroxy acid), Jessner's solution, modified Jessner's solution, resorcinol and TCA are the most common agents in superficial peel. These substances promote keratin loss and accelerates the cellular cycle. It removes the superficial layer of the keratin to soften the skin and alleviate pigmented lesions.
AHA
AHA types include glycolic acid derived from sugar canes, lactic acid derived from sour milk, citric acid obtained from citrus fruit, and phytic acid derived from rice. hydroxy acid has its origins in Ancient Egypt and is known to be used by Cleopatra as a rejuvenating facial. Aged skin is wrinkled and mottled as well as drier than young skin. Most dermatologists AHA often forgets that AHA has excellent moisturizing effect. This excellent humectant has the tendency to retain moisture in the skin. It improves skin elasticity and normalizes stratum corneum thereby effectively hydrating dry skin. Once keratin loss is promoted, the skin takes on a softer and glowing appearance. Many patients fear that their skin may turn sensitive after AHA. I think this is because of ingredients other than AHA[i]. AHA acts to reduce common skin irritation. It remains to be proven but AHA has been said to strengthen the skin barrier function. A study compared glycolic acid, lactic acid, tartaric acid, and gluconolactone and found that all types of AHA protected the skin against 5% sodium lauryl sulfate. Applying AHA had no effect on the change of TEWL[ii]. AHA can induce separation of stratum corneum, however, does not affect the integrity of the skin barrier. The mechanism by which AHA brings this effect is not clearly understood.
Glycolic Acid (GA)
Glycolic acid (GA) is the most commonly used AHA agent for chemical peel in clinical dermatology. It can be carried out over a lunch break with minimal downtime or discomfort, giving it a nickname of “lunch time peel.” Patients can return to daily activities immediately after the procedure. GA is one of the easiest chemical peels to perform. GA has anti-inflammatory, keratolytic, and anti-oxidative actions. The intensity of peel differs depending on the acid concentration, type of vehicle, applied amount, and techniques[iii]. Moreover, AHA penetrates the skin easily and can be used as superficial or medium-depth peel. Main indications include acne, acne scar, melisma, PIH, photo-aging, and excess sebum, etc. It normalizes keratinization when used in acne and increases the epidermal and dermal hyaluronic acid and collagen gene expression[iv].
In 1996, Ditre reported that topical application of AHA led to 25% increase of skin thickness and an increase in dermal mucopolysaccharide to improve elastin quality as well as collagen density and reduces histological aging signs[v]. An animal study also demonstrated that GA significantly lowered the wrinkle score and increased collagenesis[vi]. Increased collagenesis following AHA treatment was found in both in vivo and in vitro studies. GA increased collagenesis and fibroblast differentiation in in vitro study. GA is affordable and easy to use but must be neutralized to prevent burn. It is not suitable to be used over an extensive area such as in the torso and should be limited to small local areas which can be quickly neutralized.
Using 35% GA and 50% GA peeling agents once every three weeks for 10 weeks in Asians with Fitzpatrick skin type IV resulted in improved comedone and acne. Skin tone, pores and texture also improved[vii]. GA peel is frequently used in acne but does not impact sebum production[viii]. Topical application of 55~75% GA and 10~15% TCA peeling agents on resistant melisma showed that TCA improved melisma more effectively than GA. However, the TCA (25%) showed higher rate of recurrence compared to GA group (5.9%)[ix]. Another study examining the effect of 15% TCA and 35% GA on melisma found no statistical differences. Both groups had lower MASI score, indicating improved melisma. However, TCA was more often associated with side effects than GA[x]. With the rising popularity of regular manicure and pedicure, many nail artists present damaged nail plate and pigmented nails due to frequent exposure to acetone and nail polish chemicals. A study reported that 70% GA can be used to restore the nail’s smoothness and sheen[xi]. GA can be used in all skin types in the concentrations of 20~70% and it is advisable to gradually increase the concentration from the initial low concentration. A higher concentration should be tried with the interval of 2 weeks. GA requires immediate neutralization but it is difficult to determine the end-point for erythema in dark-skinned patients. In such cases, it is a good idea to begin neutralization 3-5 minutes after application of GA. People with darker skin tones can be more susceptible to PIH and scrub exfoliation, waxing, whitening or laser hair removal should be stopped at least 1 week before peeling. Scrub cleanser, exposure to hot steam or exfoliating agent, etc. should be avoided after a GA peel. It is important to moisturize and protect the skin from the UV rays.
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[i] Yu R, Van Scott E. Bioavailability of alpha-hydroxyacids in topical formaulations. Cosmet Dermatol. 1996;9:54
[ii] Berardesca E, Distante F, Vignoli GP, et al. Alpha hydroxyacids modulate stratum corneum barrier function. Br J Dermatol. 1997;137:934
[iii] Brody HJ. Chemical Peeling. St Louis: Mosby-Year Book; 1992.
[iv] Bernstein EF, Lee J, Brown DB, et al Glycolic acid treatment increases type I collagen mRNA and hyaluronic acid content of human skin. Dermatol Surg. 2001 May; 27 (5):429-33.
v] Ditre CM, Griffin TD, Murphy GF, et al. Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrasutructural study. J Am Acad Dermatol. 1996;34:187
[vi] Moon SE, Park SB, Ahn Ht, et al. The effect of glycolic acid on phtoaged albino hairless mouse skim. Dermatol Sur. 1999;25:179
[vii] Wang CM, Huang CL, Hu CT, et al. The effect of glycolic acid on the treatment of acne in Asian skin. Dermatol Surg. 1997 Jan; 23 (1):23-9.
[viii] Lee SH, Huh CH, Park KC, et al. Effects of repetitive superficial chemical peels on facial sebum secretion in acne patients. J Eur Acad Dermatol Venereol. 2006;20:964
[ix] Kalla G, Garg A, Kachhawa DChemical peeling–glycolic acid versus trichloroacetic acid in melasma. Indian J Dermatol Venereol Leprol. 2001 Mar-Apr; 67 (2):82-4.
[x] Puri N. Comparative study of 15% TCA peel versus 35% glycolic acid peel for the treatment of melasma. Dermatol Online J. 2012 May; 3 (2):109-13.
[xi] Banga G, Patel K. Glycolic Acid peels for nail rejuvenation. J Cutan Aesthet Surg. 2014 Oct-Dec;7 (4):198-201
-To be continued-
