Can You Mix Glycolic Acid and Kojic Acid?

Why

Kojic acid is a brightening agent derived from fungi, produced during the fermentation of foods such as rice for sake. It works by inhibiting tyrosinase, the copper-dependent enzyme that manufactures melanin, so it slows new pigment. Glycolic acid comes at pigmentation from the surface instead, as an AHA that exfoliates dead cells already carrying melanin, revealing brighter skin underneath. Combining a production blocker with a surface exfoliant is a logical, additive approach to dark marks and uneven tone. The trade-off is tolerance. Glycolic brings the usual AHA sting, dryness and raised UV sensitivity, and kojic acid, while effective, is more prone than gentler brighteners like arbutin to causing irritation and, in some people, contact sensitisation with prolonged use. Stacking two potentially irritating actives means the barrier can be pushed too far, and since inflammation itself can trigger more pigment, over-doing this combination can be self-defeating. Modest strengths, gradual introduction and strong sun protection keep it working in your favour.

How to combine them

Go slowly and watch your skin. A gentle structure is kojic acid in the morning under sunscreen and glycolic acid a couple of evenings a week. Morning: cleanse, apply kojic acid, moisturise, then broad-spectrum SPF 30+, which is essential for any brightening routine. Evening: cleanse, on acid nights apply glycolic to dry skin then moisturiser; on other nights use kojic acid or just moisturiser. If layering together once tolerant, apply glycolic first, wait a few minutes, then kojic acid. Because kojic acid can sensitise, patch test a new product on the inner arm for a few days before facial use, and stop if you develop itching or a rash. Keep the rest of the routine simple and hydrating, and do not increase both at once.