Kojic Acid

What Is Kojic Acid in Skincare?

Kojic acid is a natural compound produced by fungi, most famously Aspergillus oryzae, the koji mold used to ferment sake, soy sauce, and rice. In skincare it is used as a brightening ingredient: it helps dark spots, sun spots, and uneven patches look lighter by slowing the skin's production of melanin. It is also an antioxidant.

EWG Skin Deep rating for Kojic Acid

Kojic acid is effective but has firm safety limits. Safety panels in the United States and the United Kingdom have concluded it is safe in cosmetics at up to 1%, which is lower than many DIY recipes online suggest.

Quick Facts

How Kojic Acid Works on the Skin

Melanin is made in pigment cells through a chain of reactions driven by the enzyme tyrosinase, which needs copper to work. Kojic acid binds that copper and slows tyrosinase, so less new melanin is made. Over time, as the skin renews, dark spots and patches look lighter and tone looks more even. Because it works on new pigment, results build gradually and depend on daily sun protection.

Kojic acid is also an antioxidant and has antimicrobial activity in the lab, which is why it shows up in soaps and cleansers as well as serums.

What the safety research found

• The Cosmetic Ingredient Review Expert Panel (Burnett and colleagues, International Journal of Toxicology, 2010) concluded kojic acid is safe in cosmetics at up to 1%. The panel's concerns, skin sensitization and unintended lightening, were not expected below that level; human sensitization data supported safety at 2% in leave-on products, and lightening was seen in guinea pig studies at 4% but not at 1%.
• The European Commission's Scientific Committee on Consumer Safety reviewed kojic acid again in 2022 (opinion SCCS/1637/21, with a corrigendum in June 2022). The UK Scientific Advisory Group on Chemical Safety then concluded in February 2023 that kojic acid is safe at up to 1% in face cream (including the neck) and hand cream.

How to Use Kojic Acid in DIY Formulas

• Respect the 1% ceiling. In 1 fl oz (30 ml) of serum, 1% is about 0.3 g of powder. Weigh it on a scale that reads to 0.01 g; do not measure by the spoon.
• Dissolve it in the water phase and add it during cool-down, below 40°C (104°F). Kojic dipalmitate goes into the oil phase.
• Avoid discoloration. Kojic acid turns yellow to brown with light, air, heat, and traces of iron. Use distilled water, add a chelating agent, avoid metal tools, and package in opaque, airless bottles.
• Keep the formula mildly acidic and check pH after adding it.
• Combine thoughtfully. Pair it with gentler brighteners that act at different steps, such as licorice root or alpha arbutin, rather than raising the kojic acid percentage. Avoid layering it with strong peels on the same night.
• Preserve and store. Use a broad-spectrum preservative and store cool and dark. A noticeable color change means the kojic acid has oxidized.

Who Kojic Acid Suits

Kojic acid suits normal, combination, oily, and mature skin with sun spots or uneven tone. It is not ideal for very reactive skin, and it should not be used on broken, freshly peeled, or irritated skin, where more can be absorbed. If you have sensitive skin, patch test first on the inner arm for 24 hours and start at the lowest rate (a rinse-off cleanser, or a leave-on product well below 1%, used every other night), then work up. If you are pregnant or nursing, ask your doctor before using brightening actives.

Frequently Asked Questions

What does kojic acid do for your skin?

Kojic acid helps dark spots and uneven patches look lighter by slowing tyrosinase, the enzyme that drives melanin production. It also acts as an antioxidant. Results build gradually as skin renews, so consistent use and daily sunscreen matter.

Is kojic acid safe to use?

Yes, at the right concentration. Safety panels in the United States and the United Kingdom concluded it is safe at up to 1% in leave-on face and hand products. Higher levels raise the risk of skin sensitization.

What are the side effects of kojic acid?

The most common are redness, stinging, and contact sensitivity, especially at high concentrations or on damaged skin. Stop using it if irritation persists, and always patch test first.

Can I use kojic acid every day?

Many people can use a 1% or lower product daily once their skin is used to it. Start every other night, then increase if your skin stays comfortable. Daily broad-spectrum sunscreen is essential.

What is the difference between kojic acid and kojic dipalmitate?

Kojic dipalmitate is an oil-soluble ester of kojic acid. It is more resistant to discoloration and suits oil-based formulas, while kojic acid itself is water soluble. The 1% safety conclusions discussed here apply to kojic acid.

Can I use kojic acid with vitamin C or niacinamide?

Yes. Kojic acid is often combined with vitamin C, niacinamide, licorice, and arbutin in brightening routines. Introduce one new active at a time so you can see how your skin responds.

Shop and Learn More

This collection includes the Watermelon Brightening Tonic Facial Mist, a lightweight prep step for a brighter-looking routine. For a step-by-step DIY guide, read our Kojic Acid Powder Guide.

Sources

• Burnett CL, Bergfeld WF, Belsito DV, et al. Final report of the safety assessment of kojic acid as used in cosmetics. Int J Toxicol. 2010;29(6 Suppl):244S-273S. doi:10.1177/1091581810385956
• European Commission Scientific Committee on Consumer Safety. Opinion on Kojic Acid, SCCS/1637/21, final version March 2022, corrigendum 10 June 2022. European Commission
• UK Scientific Advisory Group on Chemical Safety of Non-Food and Non-Medicinal Consumer Products. Opinion 10: Kojic acid in cosmetic products. February 2023. GOV.UK

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

About the Author
Written by Kari Thomas, cosmetic formulator and founder of Skin Perfection.