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Kojic acid, a product derived from several species of fungi, is known to limit melanin production -- the substance that gives skin its color. Consequently, kojic acid is a common ingredient in skin lightening or depigmenting products. Kojic acid can cause some side effects, particularly for those with sensitive skin. However, the Cosmetic Ingredient Review (CIR) Expert Panel has determined concentrations up to 1 percent kojic acid are considered safe to use in cosmetics, as published in the November-December 2010 issue of “International Journal of Toxicology.”

Contact Dermatitis

Contact dermatitis is the most common side effect of topical kojic acid use. This irritation and inflammation of the skin may lead to a rash and red, swollen skin. Dermatitis is more likely to occur from products with kojic acid concentrations greater than 1 percent, according to the review in “International Journal of Toxicology.” However, the amount of kojic acid in most skincare products is usually not enough to trigger irritation, unless the user has particularly sensitive skin. To counter any potential irritation, some higher strength kojic acid products contain topical corticosteroids.

Delayed Dermatitis

Even if kojic acid does not initially irritate the skin, there’s a risk of developing allergic contact dermatitis with continued use. This high sensitizing potential was noted in research published in the January 1995 issue of “Contact Dermatitis.” In this small study, over half of participants using kojic acid developed facial dermatitis 1 to 12 months after starting its use. Kojic acid products are typically used short term -- 1 to 2 months or until desired results are achieved. Consult with your dermatologist prior to long-term use and discontinue use if you have any side effects.

Safety Issues

Extensive animal studies have been completed on the safety of kojic acid, as this substance can be absorbed through the skin and kojic acid is also used as a food additive. According to the review published in “International Journal of Toxicology,” animal research has linked kojic acid to cell mutation and weak carcinogenic effects. However, this published report of the CIR Expert Panel, an independent trade association that reviews the safety of cosmetic products, concluded skin products with 1 percent or lower kojic acid concentrations pose no human safety issues -- in part due to the insignificant absorption into the human body.


If you are interested in using a skin lightening product, ask your dermatologist about safe and effective options. Products with kojic acid may be an option, and your dermatologist can provide advice on frequency, dose and length of use. If you experience any rash, redness, itchiness or swelling from a skin lightening product, discontinue use. Long-term use of any skin lightening product may increase the risk of sunburn, so use sunscreen as directed.