Kojic acid is a by-product in the fermentation process of malting rice for use in the manufacturing of sake, the Japanese rice wine. There is convincing research—both in vitro (in a test tube) and in vivo (on a live subject)—showing kojic acid to be effective for inhibiting melanin production (Source: Archives of Pharmacal Research, August 2001, pages 307-311). Glycolic or kojic acid, or glycolic acid with hydroquinone, are highly effective in reducing the pigment in melasma patients (Source: Dermatological Surgery, May, 1996 pages 443-447). So why aren’t there more products available containing kojic acid? Because it is an extremely unstable ingredient in cosmetic formulations. Upon exposure to air or sunlight it can turn a strange shade of brown and lose its efficacy. Many cosmetic companies use kojic dipalmitate as an alternative because it is far more stable in formulations. However, there is no research showing kojic dipalmitate to be as effective as kojic acid, although is it a good antioxidant. Further, some controversial research has shown kojic acid to have some carcinogenic properties (Sources: Mutation Research, Genetic Toxicology and Environmental Mutagenesis, June 2005, pages 133-1450 and Toxicological Sciences, September 2004, pages 43-49).