Chemical peels — controlled chemical exfoliation to remove damaged skin layers and stimulate regeneration — are among the most performed in-office cosmetic procedures globally, with glycolic acid (GA, an alpha-hydroxy acid) peels being the most popular superficial chemical peel modality. Understanding the pharmacology of GA, how to control peel depth, and which conditions respond to which protocols enables safe and effective in-office skin rejuvenation.
Mechanism and Depth Control
GA penetration and efficacy is determined by three factors: concentration (20–70%), pH (lower pH = more ionized acid = greater penetration), and contact time. At the same concentration, a peel formulated at pH 2.0 penetrates significantly deeper than one at pH 3.5 — making pH as important as concentration in peel selection. Superficial peels (0.06mm depth — epidermis only): 20–50% GA at pH 2.5–3.5, 2–5 minutes contact. Appropriate for maintenance, first-time patients, darker skin types. Superficial-medium peels (0.45mm depth — papillary dermis): 50–70% GA at pH ≤2.0, 5–10 minutes or until frosting. Requires careful patient selection and endpoint monitoring. Endpoint recognition: erythema (superficial), even frosting (papillary dermis) — not blotchy frosting (uneven penetration and scarring risk). Frosting results from protein coagulation and indicates papillary dermis penetration.
Clinical Evidence by Indication
Acne vulgaris: 30–70% GA peels (serial, every 2–4 weeks × 6) reduce open and closed comedones by 55% and inflammatory lesions by 45% in RCTs — additive to topical retinoids and benzoyl peroxide. Solar lentigines and photodamage: 50–70% GA peel series significantly reduces wrinkle depth, mottled pigmentation, and skin roughness — comparable to 0.025% retinoic acid over 6 months in RCT comparison. Melasma: GA peel + HQ/kojic acid combination significantly more effective than topical treatment alone — peel enhances penetration of topical agents and directly exfoliates melanin-laden corneocytes. Fitzpatrick type V-VI: Use lower concentrations (20–35%), higher pH (≥3.0), and shorter contact times to minimize PIH risk — mandatory post-peel broad-spectrum SPF 50+ use. Pre-treatment with HQ 4% for 4 weeks reduces PIH risk in darker skin types. Our skin care catalog includes post-peel care products, and our wound care supplies include gentle dressings for post-procedure skin management.
