Frequently Asked Questions
What is kojic acid, and what does it do?
Kojic acid is a substance found in fungi—that is, mushrooms, according to Dr. Graf. It is well known for its skin-lightening properties, as it acts as a tyrosinase inhibitor (which, as we said, disrupts and slows down the pigment production process, leading to less pigmentation and therefore, more skin tone). Unlike, say, salicylic acid, its primary function on the skin does not involve exfoliation.
“Tyrosinase inhibitors are often used in skin care products because of their ability to help with dark spots and uneven skin tone,” said Dr. Woolery-Lloyd. They also work best in groups, which is why you can get kojic acid paired with other tyrosinase inhibitors like vitamin C, licorice extract, and tranexamic acid. (The benefit of vitamin C is that it also acts as an antioxidant, thereby reducing the free radicals that can result More discoloration when left unchecked.)
Since acne scars, sun spots, and hyperpigmentation are helpful in a multi-pronged way, you’ll also find it next to niacinamide, which works in a different way—by preventing the transfer of melanosomes, or pigment bundles, to the skin’s surface, if you want to be nerdy about it—to even out skin tone. Since it’s an active ingredient, you’ll often find it in facial serums and treatments instead of toners and cleansers—as they allow for higher concentrations.
According to Dr. Shirazi, the sweet spot of kojic acid in serum is 1 to 2%. “Kojic acid needs to be in the first five ingredients listed on the bottle to mean it really does the job,” he said.
What are the possible side effects of kojic acid?
Although in the levels found in commercial products, kojic acid is unlikely to have side effects, it can cause “skin irritation, redness, and dryness, especially in high concentrations or long-term use,” says Dr. Graf. For that reason, if you know you have sensitive skin, consider trying a patch or taking a step-by-step approach (use it twice a week and work your way up from there).
And, although the use of sunscreen should be a habit anyway—especially if you’re dealing with discoloration—”it can also increase the skin’s sensitivity to sunlight, so I recommend always wearing sunscreen during use,” he said.
How long does kojic acid take to work?
Although it may vary from person to person, “some may see skin improvement and a reduction in dark spots within four to six weeks of regular use,” says Dr. Graf. Also, that assumes you’re wearing sunscreen, as sun exposure can reverse kojic acid’s hard work. And he warns that severe hyperpigmentation can take a long time to disappear—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 use. According to Dobos, skin care products with a very low pH, such as 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 reduce the risk of a negative reaction, Dobos recommends doing a patch test before introducing kojic acid into your system. Also, if you regularly use a retinoid, another use of both – retinol on one night, kojic acid on the other.
Meet the experts
- Azadeh Shirazi, MD, is a board-certified dermatologist in La Jolla, CA
- Heather Woolery-Lloyd, MD, is a board-certified dermatologist in Miami, Florida
- Jeanette Graf, MD is a board-certified dermatologist in New York, New York
- Nicole Lee, MD, is a board-certified dermatologist in Garden City, New York
- Reshmi Kapoor, MD, is a board-certified dermatologist in New York City
How we test and review products
When Seduction reviews the product, our editors look at it from all sides to help you better. We review ingredients, scrutinize product claims, and, when necessary, examine peer-reviewed scientific and medical studies. In addition to testing each product included in every review, we rely on experts who shape their fields, including dermatology, cosmetic chemistry, and medicine, to help us evaluate ingredients and formulas.
To come up with our list of the best kojic acid products, we considered each product’s performance in five main categories: product ingredients and effectiveness, packaging, fragrance, texture, and product longevity. Every product is determined to be a winner in each category by our editorial team, made up of in-house writers and editors and contributors — with special consideration from board-certified dermatologists. To learn more information about our reporting and evaluation processes, read our full review process and how-to page.
Our staff and inspectors
When Seduction reviews the product, our editors look at it from all angles in an effort to help you better. We review ingredients, scrutinize product claims, and, when necessary, examine peer-reviewed scientific and medical studies. In addition to testing each product included in each review, we rely on experts in their fields, including dermatology, cosmetic chemistry, and medicine, to help us evaluate ingredients and formulas.
To come up with our list of the best kojic acid products, we considered each product’s performance in five main categories: product ingredients and effectiveness, packaging, fragrance, texture, and product longevity. Every product is determined to be a winner in each category by our editorial team, made up of in-house writers and editors and contributors—with special consideration from dermatologists. To learn more information about our reporting and evaluation processes, read our full review process and how-to page.
