Kojic Acid

Kojic acid is 曲酸 (qū suān) in Chinese, written 麴酸 in Traditional Chinese/Taiwan. It's a fungal-derived brightening ingredient that fades dark spots by inhibiting tyrosinase, the enzyme behind melanin production.

Their mechanisms differ: kojic acid inhibits tyrosinase directly, so it acts faster; arbutin must be converted by the skin first — slower, but possibly longer-lasting. They actually work best together: the combo shows stronger spot-fading in clinical trials. By skin type, sensitive skin leans kojic acid, oily skin can try arbutin.

Kojic acid itself doesn't cause rebound darkening — that usually comes from poor sun protection. Freshly renewed skin tans easily when unprotected, so wear SPF 30+ year-round while using kojic acid and don't slack on daytime sunscreen.

Yes, at the right concentration. 1-2% daily is generally well tolerated, but if your skin is currently reactive (redness, stinging), repair the barrier first — or space it out to once every 2-3 days. Start low and build up gradually.

Expect 6-8 weeks of consistent use before spots visibly fade, since pigment turnover is slow. Little may change in the first 4 weeks — that's normal, keep going. Timelines vary; deeper skin tones or heavier pigmentation can take longer.

Kojic acid degrades with light and air exposure. Store it somewhere cool and dry — the fridge works — and finish an opened product within 3-6 months. Dark or opaque packaging holds up noticeably better.