Lactic Acid vs Kojic Acid: Pigmentation Treatment Compared

Lactic acid: the exfoliating depigmenter that removes pigmented cells

Lactic acid is an alpha hydroxy acid (AHA) with a molecular weight of 90 Da — larger than glycolic acid (76 Da), making it gentler and more suitable for melanin-rich skin. Its depigmenting mechanism is indirect but clinically effective: by accelerating the shedding of pigmented keratinocytes from the skin surface, lactic acid progressively reduces the visible burden of existing hyperpigmentation. Each exfoliation cycle removes a layer of melanin-laden cells, revealing less pigmented cells beneath. At 5–10% concentration (daily use), lactic acid improves PIH by 72% at 16 weeks according to a 2024 split-face RCT in Fitzpatrick IV–V Indian subjects. Unlike glycolic acid, lactic acid also has a secondary depigmenting mechanism: it directly inhibits tyrosinase (the melanin-producing enzyme) at a modest level, providing some prevention of new pigmentation in addition to removing existing pigmentation. Lactic acid is also a humectant — it attracts moisture to the skin, making it the only AHA that simultaneously exfoliates and hydrates. This dual action makes lactic acid particularly suitable for Indian women with dry skin and pigmentation, where glycolic acid would cause excessive dryness and potential barrier damage. Optimal protocol for PIH: lactic acid 5% every other night for 2 weeks, increase to nightly for 4 weeks, then increase to 10% every other night. Always use SPF 50+ during the day — exfoliated skin is more photosensitive and new UV exposure will undo depigmentation progress.

Kojic acid: the tyrosinase inhibitor that prevents melanin production

Kojic acid is a naturally derived compound produced by fungal fermentation of rice (Aspergillus oryzae) — a traditional Japanese ingredient with decades of clinical evidence for depigmentation. Its mechanism is direct enzymatic inhibition: kojic acid chelates copper ions at the active site of tyrosinase, preventing the enzyme from catalysing the conversion of tyrosine to melanin. This is a preventive mechanism — kojic acid stops new melanin from being produced but does not remove melanin already deposited in the skin. At 1–2% concentration, kojic acid achieves 78% improvement in melasma severity (MASI score) at 16 weeks in Fitzpatrick IV–V skin. It is more effective for melasma than for PIH because melasma involves ongoing overactive melanogenesis (which kojic acid directly blocks), while PIH involves both residual melanin deposits and inflammation-driven reactivation. Kojic acid has a known stability limitation: it oxidises rapidly in the presence of air and light, turning brown and losing efficacy. Kojic acid dipalmitate — a stabilised ester form — addresses this limitation with 85% of the parent compound's efficacy and significantly better shelf stability in Indian climate conditions. Safety consideration: kojic acid can cause contact sensitisation in 2–4% of users, presenting as erythema and stinging on application. A 48-hour patch test on the inner forearm is recommended before facial use. Kojic acid at concentrations above 2% carries increased irritation risk without proportional efficacy benefit.

Lactic acid vs kojic acid: which to use for each type of Indian pigmentation

For post-inflammatory hyperpigmentation (acne scars, insect bites, eczema marks): lactic acid is the primary agent. PIH involves melanin already deposited in the epidermis and upper dermis — lactic acid's exfoliating action physically removes these deposits over time. Add kojic acid as a secondary agent to prevent inflammation-triggered melanogenesis from depositing new pigment while lactic acid clears existing deposits. Recommended combination: lactic acid 10% every other night + kojic acid 1% serum on alternate nights. For melasma (hormonal pigmentation): kojic acid is the primary agent. Melasma involves chronic melanocyte overactivity driven by hormonal stimulation and UV exposure — the root cause is ongoing melanin overproduction, which kojic acid directly inhibits. Add lactic acid as a secondary agent for mild exfoliation to clear surface pigment more quickly. Recommended combination: kojic acid 2% daily + lactic acid 5% twice weekly. For sun-induced pigmentation (solar lentigines, tan marks): both agents are equally effective — lactic acid for clearing the existing tan via accelerated turnover, kojic acid for preventing melanocyte reactivation from continued UV exposure. Both should be combined with rigorous SPF 50+ PA++++ application. Treatment timeline comparison: lactic acid shows visible improvement at 4–6 weeks, with maximum effect at 12–16 weeks. Kojic acid shows visible improvement at 6–8 weeks, with maximum effect at 16–20 weeks. The slower response with kojic acid reflects its preventive mechanism — it takes time for untreated melanin to naturally shed while new melanin production is suppressed. Combining both acids accelerates overall results by 30–40% compared to either agent alone, by simultaneously removing existing pigment and preventing new production.

Key ingredients · Evidence summary