Kojic acid is a chemical produced from different types of fungi. It is also a by-product of fermented soy sauce and rice wine.
Kojic acid is sometimes used in the food industry as a natural preservative. One of the main uses of kojic acid, however, is in some health and cosmetic products. Kojic acid is used in health and beauty products to lighten the skin. It may be used to treat skin conditions, such as sun damage, scars, and age spots.
The science behind how kojic acid works as a lightening agent involves its effect on melanin production.
Melanin is a naturally occurring pigment in the body that gives the eyes, hair, and skin their color. An amino acid called tyrosine is needed to support the production of Kojic acid works by blocking tyrosine from forming, which then prevents melanin production. Decreased melanin production may have a lightening effect on the skin.
Kojic acid is most commonly used in cosmetic products, such as creams, lotions, and serums. It is also used in some soaps. Many products with kojic acid are intended for use on the hands or face.
Kojic acid should be diluted to concentrations of no more than 4 percent. A concentration of 1 to 2 percent is recommended to reduce the chance of skin irritation.