Kojic Acid

Kojic Acid is a naturally occurring organic acid that is produced during the fermentation of certain fungi. It is one of the most well-studied brightening ingredients (tyrosinase inhibitors) out there.

That's why you'll see Kojic Acid in products that target dark spots, hyperpigmentation, and general uneven skin tone. It also pairs well with other brightening actives like Alpha Arbutin, Glycolic Acid, and Vitamin C derivatives.

By latching onto the copper that the enzyme tyrosinase needs to function, Kojic Acid prevents less pigment from being made. It's so well-established that researchers regularly use it as the go-to benchmark when testing new brightening ingredients.

Some other perks include documented antioxidant and antimicrobial properties. The The CIR (Cosmetic Ingredient Review) Expert Panel concluded Kojic Acid is safe for use in cosmetic products at concentrations up to 1% and the EU's SCCS (Scientific Committee on Consumer Safety) considers it safe as a skin lightening agent at concentrations up to 0.7%.

One thing to know about Kojic Acid is that stability is its weak spot; it is sensitive to light, heat, and air exposure and will oxidize/turn brown in formulations. Its derivative, Kojic Dipalmitate, was developed as a stable alternative.

Some individuals have reported contact sensitization so be sure to patch test if you have reactive or sensitive skin.

Fun fact: It was first discovered in 1907 and naturally occurs in the production of sake, soy sauce, and miso.