Identity
a compound produced by fungi during fermentation — its skin-brightening power was first noticed on the pale hands of sake brewers. It is a long-established, globally recognised depigmenting agent, and also chemically unstable (prone to oxidising and losing potency) and, in the EU, now regulated: Regulation 2024/996 — the same package that capped retinol at 0.3% — limits kojic acid to a maximum of 1% in leave-on face and hand products. For the full readable explanation of what it is and how it works, see the companion guide, what is kojic acid?
Development & history
- Isolated in Japan in 1907 from Aspergillus oryzae (koji mould), the microorganism behind sake, miso, and soy sauce.
- Studied seriously for skin brightening from the 1980s–1990s and adopted globally as a depigmenting cosmetic active.
- Flagged by the EU in 2019 as a potential endocrine disruptor (over animal-study thyroid concerns); after SCCS review, concluded safe at 1% and capped there by Regulation 2024/996, with non-compliant products phased out through 2025.
Mechanism (as proposed)
it inhibits tyrosinase by chelating the copper ion the enzyme needs to function — disarming the pigment machinery by removing a critical part rather than jamming the assembly line. In comparative laboratory work it is one of the most consistent tyrosinase inhibitors, reducing melanin without cytotoxicity in cell studies. The mechanistic case is genuinely strong; the gap, as always, is between a clean lab result and a real-world cosmetic outcome — widened here by the EU 1% cap (most studies used 2–4%), its instability, and its tendency to be used in combination rather than alone.
Related reading
- The full readable guide: what is kojic acid?
- Where kojic acid ranks among the pigment actives, in best ingredients for dark spots and hyperpigmentation.
- Its frequent partner (different mechanism, complementary): alpha arbutin.
- The gentler brighteners it is usually combined with: niacinamide, vitamin C, and azelaic acid.
- Capped by the same EU regulation: retinol. And the non-negotiable base for any pigment work: how to use sunscreen.