Kojic Acid

What is kojic acid and what does it do?

Kojic acid is produced by certain fungi during the fermentation of rice, notably in sake and soy sauce production. It inhibits tyrosinase by binding copper at the enzyme's active site, which slows new melanin production. It also has antioxidant activity. In skincare, it is used for uneven tone, sun spots, post-inflammatory hyperpigmentation and as part of melasma combinations, often alongside glycolic acid, hydroquinone alternatives or arbutin. Kojic acid itself can be unstable and darken with air and light, so more stable esters such as kojic dipalmitate are often used, although these may be less potent. Like all brighteners, it slows new pigment rather than removing existing pigment. [1]

What does the evidence show?

Reviews describe consistent laboratory evidence for tyrosinase inhibition. Clinical studies, mostly small and often combining kojic acid with other actives, show modest improvement in melasma and hyperpigmentation; few trials test kojic acid alone against placebo. Comparisons with hydroquinone suggest it is generally less potent. It is reasonable as one component of a brightening routine rather than a lead treatment, and long-term tolerability limits continuous use for some people.

Who should avoid kojic acid?

Kojic acid is a recognised cause of contact dermatitis and sensitisation, particularly with long-term use or higher concentrations, so people with sensitive skin or a history of cosmetic allergies should patch test first. Stop if redness, itching or a rash develops. Pregnant or breastfeeding women should discuss use with a doctor.

Is kojic acid available in Singapore?

Kojic acid is used in cosmetic brightening products sold in Singapore. European safety assessors have considered concentrations up to 1% acceptable in face and hand products, and permitted strengths can vary by region. It depends on product and strength, so check with a doctor or pharmacist if a product makes strong lightening claims.

If a dark patch, breakout or irritation is not responding to what you are using, the next step is a diagnosis rather than another product. See the Skin A–Z library for related ingredients.