Kojic Acid Is Trending, But Many People Are Using It Incorrectly

Lately I can’t scroll through TikTok without seeing videos about kojic acid. These videos look like commercials for the ingredient, featuring content creators who swear it can help clear up acne, fade dark spots, and brighten skin.

TikToks about kojic acid have racked up millions of views, which might be why one of Amazon’s top 10 best-selling skin-care products is—you guessed it—a kojic acid bar soap. (You can also shop them on TikTok Shop with a few quick taps for less than the cost of a latte.)

But the hype isn’t all that it seems. Social media videos often exaggerate product claims (take microneedling serums, for example), and kojic acid is no exception. David Li, MD, a board-certified dermatologist in Boston, points out that claims by content creators that kojic acid products can “lighten up skin within a week” are simply inaccurate: “Kojic acid takes longer to work,” he says.

Ahead, board-certified dermatologists offer more clarity on this brightening ingredient, weighing in on its benefits, risks, and more.

• David Li, MD, is a board-certified dermatologist based in Boston.
• David Kim, MD, is a board-certified dermatologist based in New York City.
• Reshmi Kapoor, MD, is a board-certified dermatologist and founder of Brooklyn Dermatology in New York City.
• Corey L. Hartman, MD, is a board-certified dermatologist and founder of Skin Wellness Dermatology in Birmingham, Alabama.
• Hope Mitchell, MD, is a board-certified dermatologist and founder of Mitchell Dermatology in Ohio.

• What exactly is kojic acid?
• What are the skin-care benefits of kojic acid?
• How to use kojic acid
• How long does it take to see results?
• The best kojic acid skin-care products
• A note on kojic acid soaps and pads

Kojic acid is a byproduct of fermenting rice or soybeans with certain types of mold, like Aspergillus oryzae. In Japan, this fermentation derivative is called koji, and it’s used to make sake (rice wine), soy sauce, rice vinegar, and miso paste. Some mushrooms, such as shitake, reishi, and snow, are also natural sources of kojic acid, says board-certified dermatologist David Kim, MD.

In skin care, kojic acid is known to brighten skin by inhibiting the formation of tyrosinase, an enzyme that is essential for melanin production, as board-certified dermatologist Evan Rieder, MD, shared on The Inside Story of Kojic Acid mini-episode of Allure’s The Science of Beauty podcast.

But kojic acid doesn’t block pre-existing melanin: “Kojic acid doesn’t bleach skin or cause over-lightening of areas,” says board-certified dermatologist Reshmi Kapoor, MD. Instead, it specifically blocks the formation of new melanin that typically occurs after the skin has been inflamed due to breakouts, melasma, or sun damage, Dr. Li adds.

Because kojic acid blocks and inactivates tyrosinase, an enzyme required for melanin production, it can effectively help fade and prevent discoloration of all types, including sun damage and post-inflammatory hyperpigmentation, says Corey L. Hartman, MD, a board-certified dermatologist in Birmingham, Alabama: "It is best for anyone looking for a more naturally occurring ingredient to lighten dark spots and provide a more even complexion."