Kojic Acid Good Antioxidant Dark Spot Fading Evens Skin Tone Anti-Ageing Kojic Acid description By-product of the fermentation process of malting rice for use in the manufacture of sake (Japanese rice wine). In vitro and in vivo research and animal studies have shown that kojic acid is effective for brightening an uneven skin tone. Kojic acid’s downside is that it’s an extremely unstable ingredient in cosmetic formulations. On exposure to air or sunlight, it turns brown and loses its efficacy. Many cosmetics companies use kojic dipalmitate as an alternative because it’s more stable in formulations. However, there’s no research showing that kojic dipalmitate is as effective as kojic acid, although it’s a good antioxidant.