Produced naturally by several species of fungi during fermentation (notably Aspergillus oryzae, used in sake and soy sauce production), Kojic Acid is one of the most widely used tyrosinase inhibitors in cosmetics. It is effective for treating hyperpigmentation — but is now a restricted ingredient in the EU (Annex III, face & hand products only, ≤ 1%), with a suspected-carcinogen classification and endocrine disruption concerns that consumers should understand.
Kojic Acid (INCI: KOJIC ACID, CAS 501-30-4) is a naturally occurring compound produced by several species of Aspergillus and Penicillium fungi during aerobic fermentation. It has been used in the food industry (as a preservative and browning inhibitor) and in cosmetics as a skin lightening agent since the 1980s, primarily in Japan and Southeast Asia. It is registered in the EU CosIng database (#34801) with functions of antioxidant and skin conditioning.
Kojic Acid works by chelating copper at the active site of the tyrosinase enzyme, thereby inhibiting the conversion of L-tyrosine to L-DOPA and subsequently reducing melanin production. This mechanism is shared with several other brightening agents (such as Alpha Arbutin), but Kojic Acid is considered one of the more potent tyrosinase inhibitors available in over-the-counter cosmetics. Unlike hydroquinone — which has been banned in EU cosmetics — Kojic Acid was reviewed by the SCCS (SCCS/1637/21, 2022) and deemed safe at concentrations up to 1% for skin lightening. Following the SCCS opinion, the EU formally added Kojic Acid to Annex III of the Cosmetics Regulation via Regulation (EU) 2024/996, restricting its use to face and hand products at a maximum of 1%.
Kojic Acid carries a GHS H351 classification (suspected of causing cancer) based on thyroid follicular-cell tumour data in rodents, and there are outstanding concerns about its potential to disrupt thyroid hormone homeostasis. However, the SCCS concluded that the tumour mechanism is non-genotoxic and that humans appear less sensitive than rodents; and that the ingredient can be used safely within the restricted conditions. The CIR Expert Panel considers it "Safe with Qualifications." Our database identifies Kojic Acid in 625 product variants across 41 brands.
Kojic Acid chelates copper ions at the active site of tyrosinase, directly inhibiting the rate-limiting step of melanin synthesis. This makes it effective for addressing hyperpigmentation, melasma, age spots, and uneven skin tone. Clinical studies have demonstrated visible lightening effects after 4–8 weeks of consistent use at concentrations up to 1%.
Post-acne marks and other forms of post-inflammatory hyperpigmentation (PIH) involve excess melanin deposition. By suppressing tyrosinase activity, Kojic Acid helps prevent further melanin accumulation in healing skin. It is often used alongside other brightening agents for a multi-mechanism approach to PIH.
Kojic Acid exhibits antioxidant activity by chelating metal ions that catalyse free radical formation. This secondary property helps protect skin from oxidative stress caused by UV exposure and environmental pollutants, though its primary cosmetic use remains skin lightening rather than antioxidant protection.
Unlike synthetic brightening agents, Kojic Acid is produced through fungal fermentation — a natural biotechnological process. This origin appeals to consumers seeking ingredients with a natural provenance. However, "natural" does not equate to "safe" — its safety profile requires careful evaluation regardless of its biological origin.
May be suitable for: Those with hyperpigmentation, melasma, or uneven skin tone who are using EU-compliant products (face & hand, ≤ 1%). Those with sensitive skin, a compromised skin barrier, or thyroid conditions should consult a healthcare provider before use. Patch testing is advisable.
Kojic Acid has a GHS H351 classification (suspected of causing cancer) and endocrine disruption concerns related to thyroid hormone homeostasis. As a result, the EU has placed it on Annex III (restricted), limiting use to face and hand products at ≤ 1%. The SCCS reviewed all available data — including thyroid tumour findings — and concluded the ingredient is safe under these restricted conditions (MoS 141). The CIR rated it "Safe with Qualifications." Our 7/10 rating reflects the combination of hazard classifications and regulatory restrictions, not a recommendation against use within compliant products.
EU Annex III restricted ingredient: As of Regulation (EU) 2024/996, Kojic Acid may only be used in face and hand cosmetic products at a maximum concentration of 1%. Products exceeding this concentration or intended for other body areas are non-compliant. Always check the product labelling and INCI concentration.
H351 classification & thyroid concerns: Kojic Acid carries a GHS H351 classification (suspected of causing cancer) based on rodent thyroid follicular-cell tumour data. The SCCS evaluated this thoroughly and concluded the mechanism is non-genotoxic — it involves disruption of thyroid hormone homeostasis (decreased T3/T4, compensatory TSH increase). In vivo genotoxicity tests were negative, and evidence suggests humans are less sensitive than rodents to this mechanism. Despite limited human-specific mechanistic data, the SCCS concluded the ingredient is safe within the restricted conditions (MoS 141). The H351 classification is the reason the EU imposed Annex III restrictions — it does not mean cosmetic use at ≤ 1% has been found to be unsafe.
Endocrine disruption (thyroid axis): Kojic Acid interferes with the hypothalamic-pituitary-thyroid (HPT) axis in rats. Re-analysis of repeated-dose studies confirmed decreased serum T3/T4 followed by compensatory TSH release and thyroid cell proliferation. The NOAEL based on thyroid effects was 6 mg/kg bw/day in a 28-day rat study. The SCCS factored these concerns into its risk assessment and still concluded the ingredient is safe at ≤ 1% for face and hand use.
Sensitisation & contact dermatitis: The SCCS reported that Kojic Acid was not a sensitiser in guinea pig studies and that allergic contact dermatitis in humans is very low. However, clinical literature does report cases of contact dermatitis, particularly with higher concentrations or prolonged use. Patch testing is advisable, especially for sensitive skin.
Weakened skin barrier: The SCCS specifically noted that when Kojic Acid is added to peeling agents, a weakened skin barrier may increase dermal absorption. If using Kojic Acid alongside exfoliants or retinoids, introduce them gradually and allow skin recovery time between applications.
UV protection is essential: The SCCS reported Kojic Acid is slightly photoirritant in animal testing, though not photosensitising — it does not increase sun sensitivity the way retinoids or AHAs do. However, broad-spectrum sunscreen is essential during any brightening regimen because UV exposure drives melanin production and can reverse treatment progress.
Animal reproductive toxicity studies found that Kojic Acid did not induce malformations or affect fertility. NOAELs for maternal toxicity and embryotoxicity ranged from 100–150 mg/kg bw/day for rats, 100 mg/kg for rabbits, and 30 mg/kg for mice. However, given the endocrine disruption concerns (thyroid hormone homeostasis), the H351 carcinogen classification, and the fact that the SCCS opinion only covers topical cosmetic use at ≤ 1%, pregnant or nursing individuals should exercise extra caution. Consult your healthcare provider before use. Alternatives with better-established pregnancy safety profiles — such as Azelaic Acid, Niacinamide, or Tranexamic Acid — may be preferable during this period.
Apply a small amount of the product to the inner forearm or behind the ear and wait 24–48 hours. Kojic Acid can cause contact sensitisation in some individuals — discontinue immediately if redness, itching, or irritation develops.
After cleansing, apply your Kojic Acid product (serum, cream, or soap — ensure concentration is ≤ 1%) to areas with hyperpigmentation. Avoid broken or irritated skin, and do not apply immediately after exfoliation, as compromised skin barrier increases absorption.
Kojic Acid can be drying. Layer with a hydrating moisturiser containing ceramides or hyaluronic acid to support the skin barrier. This also helps mitigate potential irritation from the active ingredient.
Sunscreen is essential during any brightening regimen. UV exposure drives melanin production and can reverse treatment progress. Kojic Acid does not increase sun sensitivity the way retinoids or AHAs do, but the SCCS noted slight photoirritancy in animal testing. Use broad-spectrum SPF 30+ every morning.
Leave-on formulations at ≤ 1% concentration. The most effective format for targeted treatment of dark spots. Look for products that pair Kojic Acid with stabilising and soothing ingredients.
Kojic Acid soaps are extremely popular in Southeast Asia. As a wash-off product, contact time is shorter, which may reduce both efficacy and irritation risk. Commonly available at higher concentrations.
Some products target specific dark spots or patches. These allow precise application to areas that need it most while minimising whole-face exposure to the active ingredient.
Niacinamide inhibits melanosome transfer — a different mechanism from Kojic Acid's tyrosinase inhibition. Together they address pigmentation at multiple steps. Niacinamide also helps soothe skin and support the barrier, potentially offsetting Kojic Acid's drying effect.
TXA works through the plasmin pathway, independent of tyrosinase. Combining these two brightening agents targets melanin production through completely different cascades. Both are used in professional formulations for stubborn melasma.
Non-negotiable when using Kojic Acid. Sunscreen prevents UV-triggered melanin production that counteracts brightening treatment. Ceramides support the skin barrier — important because the SCCS flagged that weakened barriers increase dermal absorption of Kojic Acid.
The SCCS noted that a weakened skin barrier may increase dermal absorption of Kojic Acid. If using both, introduce gradually — for example, alternate on different days or use AHA/BHA in the evening and Kojic Acid in the morning. Avoid layering strong peels and Kojic Acid in the same routine step.
Retinoids increase skin turnover and can temporarily compromise the barrier. If combining with Kojic Acid, start with low-concentration retinoids and alternate evenings until tolerance is established. This is a precaution related to the SCCS barrier-absorption concern, not an absolute contraindication.
Both are potent tyrosinase inhibitors. Combining them may increase the risk of irritation without proportional benefit. Hydroquinone is banned in EU cosmetics; in other jurisdictions, consult a dermatologist before combining these actives.
Found in 625 product variants across 41 brands in our database. Here are some well-known options. Note: formulations may change — always check the current INCI list on the product packaging and verify the Kojic Acid concentration is ≤ 1%.
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