Alpha Hydroxy Acid

Glycolic Acid

Glycolic acid is the smallest alpha hydroxy acid, allowing it to penetrate most effectively into the epidermis. It has strong evidence for improving skin texture, reducing fine lines, treating acne, and fading pigmentation at concentrations of 5–10% (OTC) or higher (professional peels).

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Strong Evidence

Last reviewed: March 2026 · Our methodology

What It Does

Glycolic acid works by disrupting the ionic bonds (desmosomes) that hold dead corneocytes together on the skin surface, accelerating their shedding. This process (chemical exfoliation) reveals newer skin underneath, improves texture, and promotes more even melanin distribution. At higher concentrations and lower pH, glycolic acid also stimulates fibroblast collagen production and increases hyaluronic acid content in the dermis.

As the smallest AHA (molecular weight 76 Da), glycolic acid penetrates deeper than lactic acid (90 Da) or mandelic acid (152 Da). This makes it more effective but also more irritating — the trade-off is real and worth understanding.

Best Use Cases

Rough, dull skin texture
Fine lines and superficial wrinkles
Post-inflammatory hyperpigmentation
Comedonal acne (blackheads, closed comedones)
Sun damage and photoageing

Who May Benefit Most

People with dull, rough-textured skin, those with mild pigmentation, and adults seeking anti-ageing exfoliation. Best suited for normal to oily skin types. Those with sensitive skin should consider lactic or mandelic acid instead.

Cautions

Glycolic acid increases photosensitivity — daily SPF 30+ is essential. Start at 5% concentration 2–3 times per week and increase gradually. Can cause stinging, redness, and peeling, particularly at higher concentrations or on compromised skin. Not recommended during active retinoid adjustment (retinisation) — wait until skin has adapted before introducing AHA. Avoid on broken or inflamed skin.

Common Mistakes

Using daily from the start — begin 2–3 times per week
Combining with retinoids in the same PM step during the first months
Using high-concentration peels (20%+) without prior tolerance to lower concentrations
Skipping sunscreen the next day
Over-exfoliating — more is not better, and signs of barrier damage (stinging, dryness) mean you should reduce frequency

Combines Well With

Hyaluronic acid (apply after glycolic acid to replenish hydration)
Niacinamide (calming, can be used in the same routine)
Ceramide moisturisers (barrier support after exfoliation)
Sunscreen (essential)

May Combine Poorly With

Retinoids in the same PM step (use on alternate nights)
Other exfoliating acids in the same step (BHA, lactic acid)
Benzoyl peroxide in the same step
Vitamin C at very low pH in the same step (pH conflict and irritation stacking)

Realistic Timeline

Improved skin texture and brightness often noticeable within 2–4 weeks. Pigmentation improvements take 6–12 weeks. Anti-ageing collagen stimulation effects build over 3–6+ months with consistent use.

Disclaimer

Glycolic acid can cause significant irritation if misused. Start with low concentrations and build tolerance. Professional chemical peels at higher concentrations (20–70%) should only be performed by trained practitioners.