Kojic Acid

Kojic acid is a chelation-based tyrosinase inhibitor produced by Aspergillus fungi during sake fermentation. By binding copper at the enzyme’s active site, it slows melanin synthesis and gradually lightens hyperpigmentation, sun spots, and melasma at 1–4%. Kojic acid also has mild antioxidant and antibacterial properties. Its limitations: it is unstable in formulation, can oxidise to a brown colour, and causes contact dermatitis in a minority of sensitive users — patch testing is advised. Modern formulas often prefer kojic dipalmitate for stability or combine kojic acid with arbutin and vitamin C for stronger, better-tolerated brightening. Consistent use with strict sun protection is essential for lasting results.