Kojic acid

Kojic acid is a brightening compound produced by fungi, notably Aspergillus species, and is a natural byproduct of fermentation processes such as sake and soy brewing. In skincare it inhibits tyrosinase, the key enzyme in melanin production, which is the basis for its use on dark spots and uneven tone. The evidence is moderate. Clinical studies, often combining kojic acid with other agents such as hydroquinone, glycolic acid or niacinamide, support improvement in melasma and hyperpigmentation, though results for kojic acid alone are more limited and it is generally considered somewhat less potent and less stable than some alternatives. It is a credible supporting brightener rather than a standalone powerhouse. It is best for people with melasma, sun spots and post-inflammatory marks who want to layer complementary brighteners. It maps to dark-spot and dullness concerns. Layering is where it shines: kojic acid is frequently paired with niacinamide, alpha-arbutin, vitamin C or gentle acids for additive effect, and works alongside diligent sun protection. It has no strict conflicts, but stacking several brighteners and acids at once can increase irritation, so build gradually. On safety, kojic acid carries a more notable sensitization profile than many brighteners; higher concentrations and prolonged use are associated with contact dermatitis in some people, so patch testing is genuinely advisable and lower percentages are prudent. It can also oxidize and discolor over time. It does not feed Malassezia. There is limited safety data for topical kojic acid in pregnancy, so the cautious approach is to confirm with your clinician before use.