What is Kojic Acid?
Kojic acid is a fungal metabolic product that finds application as skin-lightening agent in a number of skincare products. It has been reported to be effective both therapeutically and prophylactically against pigmentation. Kojic acid reduces formation of pigment in plant and animal tissues, hence is also effective in preserving color of food substances. It was first isolated from Aspergillus in 1907. Kojic acid exerts its action by suppressing the free tyrosinase enzyme by chelating its' copper.
In Japan, nonprescription skincare products are available that contain kojic acid, generally a concentration of upto 1% is employed in skin whitening products. Most cosmetic formulators use the maximum allowed concentration by respective regulatory body to get better results. Kojic acid is used intensively in making of foods like bean, soy paste, and sake in Japan and nearing countries; this makes kojic acid a relatively safe candidate for topical use.
Shibuya and his team investigated the mutagenicity of kojic acid by forward mutation test in cultured Chinese hamster cells, dominant lethal test in mice and the Ames test . They reported kojic acid to be a mild mutagen in bacteria, but found it to be nonmutagenic in eukaryotic systems both in vivo and in vitro. In another study dilution-plate method was employed to test mycotoxins. Results indicated that kojic acid can potentially induce some toxins.
No major adverse effects after human oral ingestion have been found. When patients sensitized by kojic acid were administered kojic acid containing food orally, they did not report any adverse effect or relapse of dermatitis, however patients sensitive to kojic acid may report allergic contact dermatitis after topical application of kojic acid.
In a recent study an in vitro model was used to evaluate the stability, efficacy, and cytotoxicity of skin whitening agents. Researchers conducted a non placebo-controlled clinical study that indicated that kojic acid when incorporated with an anhydrous base is more effective skin lightening agent compared to kojic acid incorporated in an aqueous base.
According to the results of the studies using the brownish guinea pig, Ellagic Acid is a more efficient skin whitener and suppressor of pigmentation than arbutin or kojic acid, other active skin whiteners, at the same dose level (1%).
1. Hongbo Zhai and Howard I. Maibach, Handbook of Cosmetic Science and Technology 2nd Edition, Pg 460