“Kojic acid is made up of multiple different fungi,” says Jeannette Graf, board-certified dermatologist and assistant clinical professor of dermatology at Mount Sinai School of Medicine. “It is a byproduct of

certain types of mushrooms and fermented foods like rice wine, kimchi, and Japanese sake. Kojic acid inhibits tyrosinase, which is the melanin-forming enzyme.” 

In beauty products, kojic acid works as a lightening agent. “Because kojic acid inhibits tyrosinase, it can be used to lighten unwanted hyperpigmentation,” says Karen Chinonso Kagha, MD, board-certified dermatologist and Harvard-trained cosmetic and laser expert.