Kojic Acid

What is kojic acid?

Kojic acid is a natural active that forms when the mould Aspergillus oryzae – known in Japan and Korea as koji – ferments rice. The same mould has been used for centuries to make sake, soy sauce and miso. Legend has it that brewers were noticed for their especially fair, soft hands. Kojic acid has been used in skincare against dark spots since the 1980s.

How does kojic acid work?

To produce melanin, the skin needs the enzyme tyrosinase, which requires copper as a building block. Kojic acid binds this copper and so slows down tyrosinase. Less melanin means:

• Lighter dark spots and sun spots
• Faster-fading post-acne marks
• A more even, radiant complexion

Kojic acid also has mild antioxidant and antimicrobial effects.

How well tolerated is kojic acid?

Kojic acid is effective but can irritate sensitive skin or, in rare cases, cause a contact allergy. So:

• In facial products, concentrations of around 1% are common and considered safe.
• Patch test a new product on a small area first.
• If you get redness, stinging or itching, reduce use or stop.
• Use sunscreen every day – otherwise UV rays work against the active.

How to combine kojic acid

• Good: with niacinamide, tranexamic acid, alpha arbutin or vitamin C. They inhibit pigment production at other points and reinforce each other.
• Careful: with strong AHA exfoliants or retinol on the same evening – that can overwhelm the skin.

Kojic acid is a great building block in any routine for dark spots.

Kojic acid in Korean skincare

Especially well known is medicube’s Kojic Acid Turmeric line, which combines kojic acid with turmeric and niacinamide – as a serum, toner, pads and capsule cream. Also from our range: the Dark Spot Brightening Serum and the Radiant Tone Correcting Cream by KOJI WHITE, the Kojic Acid Niacinamide Radiance Soothing Gel Cleanser by SUNGBOON EDITOR and the Glutathione Kojic Acid Eye Patches by Abib. You’ll find all products in our kojic acid skincare collection.

What does the research say?

In a split-face study with melasma patients, the side of the face that additionally received 2% kojic acid improved more than the comparison side (Lim, Dermatologic Surgery, 1999). The EU Scientific Committee on Consumer Safety (SCCS) considers kojic acid safe at up to 1% in face and hand care (2022).