Kojic acid, a natural antibiotic agent, comes from koji, a culture prepared by growing molds on cooked grains or soybeans under humid conditions. Used in Japan to produce miso, soy sauce and sake, koji came into the mainstream in 1955 when Charles Pfizer and Company tried to manufacture it as an organic acid. Although the company succeeded, there was no real commercial use for kojic acid until the early 1980s, when the cosmetic industry discovered its ability to inhibit tyrosinase, the enzyme responsible for melanin formation.
The Soap's Purpose
Once the cosmetic industry understood the benefits of kojic acid, the next step was to incorporate it into skincare products such as creams, lotions and soaps. Kojic acid soap, in particular, is used as a skin lightening agent. A safer alternative to hydroquinone -- a controversial bleaching agent -- kojic acid soap has been shown effective in treating hyperpigmentation, sun spots, freckles, liver spots and other pigment issues. Kojic acid soap may also be effective in preventing photo-damage and subsequent wrinkling, according to a study done at Hacettepe University in Ankara, Turkey, published in "Medicinal Chemistry and Drug Design."