Glycolic acid and lactic acid are the two most widely used AHAs in over-the-counter skincare and clinical practice. Both exfoliate the skin’s surface by loosening the bonds between dead skin cells. Both improve texture, brightness, and pigmentation over time. But they are not interchangeable — their molecular sizes, penetration depths, and tolerability profiles are meaningfully different, and for Indian skin specifically, this distinction matters.

Glycolic Acid

Glycolic acid is the smallest AHA molecule — derived from sugarcane — and this small size allows it to penetrate most deeply and most rapidly into the skin. This makes it the most potent surface exfoliant in the AHA category: at equivalent concentrations, it produces faster and more pronounced exfoliation than other AHAs. It is the most studied AHA with the most robust clinical evidence for improving pigmentation, fine lines, and acne. However, its penetration speed also makes it more likely to cause irritation, stinging, and — in Indian skin — PIH if used at too high a concentration or too frequently. It is best suited to patients with normal to oily, non-reactive skin who have already established an exfoliation tolerance.

Lactic Acid

Lactic acid is a larger molecule — derived from milk — that penetrates more slowly and more superficially. This makes it gentler and better tolerated by sensitive, dry, or reactive skin types. It also has a humectant effect — it draws moisture to the skin surface alongside its exfoliating action — making it the superior choice for dry or dehydrated skin that needs exfoliation without further stripping. For patients beginning chemical exfoliation for the first time, and for those with darker Indian skin types where PIH risk is a primary concern, lactic acid is our preferred AHA starting point.

The Practical Guide

For oily, acne-prone, non-reactive Indian skin: glycolic acid at 5-10%, 2-3 times weekly. For dry, sensitive, or first-time exfoliation users: lactic acid at 5-10%, 1-2 times weekly. For darker skin types (Fitzpatrick IV-V) with pigmentation concerns: mandelic acid is often the best AHA choice — the largest molecule, slowest penetration, lowest PIH risk. Always follow any AHA application with SPF the next morning. Never use AHAs alongside retinoids in the same routine without building tolerance first.

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— Dr. Nishita Ranka | Consultant Dermatologist | Dr. Nishita’s Clinic for Skin, Hair & Aesthetics, Hyderabad