What it does
- Helps reduce the appearance of hyperpigmentation and post-blemish marks.
- A well-known naturally derived brightening active, often used with arbutin or vitamin C.
How it works
Kojic acid is widely documented to chelate copper at the active site of tyrosinase, inhibiting the enzyme and thereby reducing melanin synthesis. Its main practical challenge is stability: it can oxidise and discolour (turning yellow-brown) on exposure to air, light and metal ions.
Use level
- Typical use level
- typically up to ~1–2%
Often used at up to about 1%, sometimes to 2%. Because of stability and tolerance considerations, many formulators favour the lower end or use kojic dipalmitate (a more stable ester) instead of free kojic acid.
Formulation considerations
- Water-soluble; prone to oxidation and discolouration.
- Use chelators and antioxidants and protect from light; opaque packaging helps.
- Most stable in mildly acidic products; avoid iron contact.
- Can be sensitising at higher levels in reactive skin.
What it pairs with & what to avoid
Pairs well with
- Alpha arbutin
- Vitamin C derivatives
- Niacinamide
- Chelators/antioxidants (for stability)
Use with care / avoid
- Iron and other metal ions (accelerate discolouration)
- High pH and light exposure
Regulatory status
Kojic acid is listed in the EU CosIng database. Some regions apply maximum-concentration guidance for cosmetic use; formulators should check the current local limit for their market.
Common questions
What percentage of kojic acid is effective?
Commonly up to about 1%, sometimes to 2%. Stability and tolerance often make the lower end preferable, or a stable ester such as kojic dipalmitate is used.
Why does my kojic acid product turn brown?
Kojic acid oxidises with air, light and metal ions. Antioxidants, chelators and opaque packaging help prevent discolouration.
Is kojic acid better than arbutin?
Neither is universally better. Kojic acid can be effective but is less stable and can be more irritating; arbutin is gentler and more stable. They are sometimes combined.