Kojic acid is a by-product in the fermentation process of malting rice when making the Japanese rice wine. Similar to hydroquinone, it inhibits the enzyme tyrosinase, as explained above. This action is achieved through binding the copper ions, which is need to activate the tyrosinase.

Kojic acid is usually combined with other whiteners in use, for example glycolic acid. It is a much safer alternative to skin bleaching than hydroquinone, without the nasty side effects mentioned.

Kojic acid is not very stable and its colour can change after oxidation. Kojic dipalmitate is a good alternative as it is much more stable in formulations, and also has the added benefit of being an excellent anti-oxidant.