Frequently Asked Questions
What is kojic acid, and what does it do?
Kojic acid is a substance derived by funghi—namely, mushrooms, according to Dr. Graf. It’s best known for its skin-brightening properties, since it acts as a tyrosinase inhibitor (which, like we mentioned, interferes with and slows the pigment production process, resulting in less pigment and therefore, more even skin tone). Unlike, say, salicylic acid, its primary function in skin doesn’t involve exfoliation.
“Tyrosinase inhibitors are commonly used in skin care products due to their ability to help with dark spots and uneven skin tone,” says Dr. Woolery-Lloyd. And they work best in groups, which is why you can find kojic acid paired with other tyrosinase inhibitors like vitamin C, licorice extract, and tranexamic acid. (The benefit of vitamin C is that it also functions as an antioxidant, thus neutralizing the free radicals that can lead to more discoloration when left unchecked.)
Since acne scars, sun spots, and hyperpigmentation benefit from a multi-pronged approach, you’ll also find it alongside niacinamide, which works in a different way—by inhibiting the transfer of melanosomes, or bundles of pigment, to skin’s surface, if you want to get nerdy about it—to even out skin tone. As it’s an active ingredient, you can usually find it in face serums and treatments instead of toners and cleansers—as they allow for high concentrations.
According to Dr. Shirazi, the sweet spot for kojic acid in a serum is 1 to 2%. “Kojic acid needs to be in the first five ingredients mentioned on the bottle to mean it’s actually doing the work,” she says.
What are the potential side effects of kojic acid?
While at the levels found in over-the-counter products, kojic acid is unlikely to have any side effects, it can cause “skin irritation, redness, and dryness, especially with higher concentrations or prolonged use,” says Dr. Graf. For that reason, if you know you have sensitive skin, consider patch-testing it or taking a gradual approach (use it twice a week and work your way up from there).
And, although sunscreen use should be a habit anyway—especially if you’re dealing with discoloration—“it can also increase skin’s sensitivity to sunlight, so I recommend always wearing sun protection during use,” she says.
How long does kojic acid take to work?
While it can vary from person to person, “some may see improvements in skin tone and a reduction of dark spots within four to six weeks of consistent use,” says Dr. Graf. Again, that assumes you’re wearing sunscreen, since sun exposure can undo kojic acid’s hard work. And she does warn that severe hyperpigmentation can take longer to fade—think three months or more.
What should you not use with kojic acid?
When using kojic acid, it’s important to be aware of the ingredients in other formulas you’re using. According to Dobos, skin-care products with a very low pH, like those containing AHAs or BHAs, can lead to increased irritation and dryness when paired with kojic acid.
Dr. Greenfield also advises against using harsh acids or prescription retinoids alongside kojic acid, as they can further irritate the skin. To minimize the risk of adverse reactions, Dobos recommends performing a patch test before introducing kojic acid into your routine. Also, if you regularly use a retinoid, alternate usage of the two—retinol one night, kojic acid on the other.
Meet the experts
- Azadeh Shirazi, MD, a board-certified dermatologist in La Jolla, CA
- Heather Woolery-Lloyd, MD, a board-certified dermatologist in Miami, Florida
- Jeanette Graf, MD a board-certified dermatologist in New York, New York
- Nicole Lee, MD, board-certified dermatologist in Garden City, New York
- Reshmi Kapoor, MD, a board-certified dermatologist in New York City
How we test and review products
When Allure tests a product, our editors look at it from every angle to best serve you. We review ingredients, scrutinize brand claims, and, when necessary, examine peer-reviewed scientific and medical studies. In addition to testing each and every product that’s included in every review, we rely on experts who shape their fields, including dermatology, cosmetic chemistry, and medicine, to help us vet the ingredients and formulas.
For our list of the best kojic acid products, we considered each product’s performance across five primary categories: product ingredients and efficacy, packaging, fragrance, texture, and product wear. Every product was determined to have excelled in each category by our editorial team, which is composed of in-house writers and editors as well as contributors — along with special consideration from board-certified dermatologists. To learn more information on our reporting and testing processes, read our complete reviews process and methodology page.
Our staff and testers
When Allure tests a product, our editors look at it from every angle in an effort to best serve you. We review ingredients, scrutinize brand claims, and, when necessary, examine peer-reviewed scientific and medical studies. In addition to testing each and every product that’s included in each and every review, we rely on experts who shape their fields, including dermatology, cosmetic chemistry, and medicine, to help us vet the ingredients and formulas.
For our list of the best kojic acid products, we considered each product’s performance across five primary categories: product ingredients and efficacy, packaging, fragrance, texture, and product wear. Every product was determined to have excelled in each category by our editorial team, which is composed of in-house writers and editors as well as contributors—along with special consideration from dermatologists. To learn more information on our reporting and testing processes, read our complete reviews process and methodology page.
