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 remains popular for treating hyperpigmentation — but carries significant safety flags including a suspected-carcinogen classification, endocrine disruption concerns, and EU Annex III restricted status that consumers should understand.
曲酸（INCI：KOJIC ACID，CAS 501-30-4）是由数种 Aspergillus 和 Penicillium 真菌在有氧发酵过程中产生的天然化合物。自 1980 年代以来，它一直被用于食品工业（作为防腐剂和抑褐剂）和化妆品中作为美白剂，主要在日本和东南亚使用。它在欧盟 CosIng 数据库（#34801）中注册，具有抗氧化和皮肤调理功能。
曲酸通过螯合酪氨酸酶活性位点的铜离子，从而抑制 L-酪氨酸向 L-DOPA 的转化，随后减少黑色素的生成。这个机制被其他几种美白剂（如 Alpha 熊果苷）共享，但曲酸被认为是非处方化妆品中效力较强的酪氨酸酶抑制剂之一。与对苯二酚不同（对苯二酚因安全问题已在欧盟化妆品中禁用），曲酸经过 SCCS 审查，被认为在浓度达 1% 时用于美白是安全的（SCCS/1637/21，2022）。根据欧盟法规 2024/996（附录III），曲酸现在是受限制成分，仅可用于面部和手部产品，最高浓度为 1%。
然而，曲酸带有 GHS H351 分类（疑似致癌），基于啮齿动物的甲状腺滤泡细胞肿瘤数据，并且存在关于其可能破坏甲状腺激素稳态的未解决顾虑。CIR 专家小组认为它"有条件的安全"。我们的数据库识别 41 个品牌中的 625 个产品变体中含有曲酸。虽然有效，但它是一种需要知情使用和了解其安全档案的成分。
曲酸在酪氨酸酶活性位点螯合铜离子，直接抑制黑色素合成的速率限制步骤。这使其对于解决色素沉着、黄褐斑、老年斑和肤色不均有效。临床研究表明，在浓度达 1% 的情况下持续使用 4–8 周后，可见明显的美白效果。
痤疮后痕迹和其他形式的炎症后色素沉着（PIH）涉及黑色素过量沉积。通过抑制酪氨酸酶活性，曲酸有助于防止愈合皮肤中进一步的黑色素积累。它通常与其他美白剂一起使用，以采用多机制方法来解决 PIH。
曲酸通过螯合催化自由基形成的金属离子来展现抗氧化活性。这个次要特性有助于保护皮肤免受 UV 暴露和环境污染物引起的氧化应激，尽管其主要化妆品用途仍然是皮肤美白而不是抗氧化保护。
与合成美白剂不同，曲酸是通过真菌发酵 — 一种天然生物技术过程生成的。这种来源吸引了寻求具有自然来源的成分的消费者。然而，"天然"并不等于"安全" — 无论其生物来源如何，其安全档案需要仔细评估。
May be suitable for: Those with hyperpigmentation, melasma, or uneven skin tone who have assessed the safety profile and are using products with ≤ 1% concentration. Not recommended for those with sensitive skin, compromised skin barrier, or thyroid conditions without consulting a healthcare provider. Patch testing is advisable due to potential for contact sensitisation in some individuals.
Kojic Acid carries a GHS H351 classification (suspected of causing cancer) based on thyroid tumour data in rodents, with unresolved concerns about endocrine disruption affecting thyroid hormone homeostasis. The SCCS concluded it is safe at ≤ 1% for skin lightening, and the CIR rated it "Safe with Qualifications." The 7/10 risk score reflects hazard classifications and regulatory restrictions, not a recommendation against use. When used at or below the regulated concentration limit and on appropriate body areas (face, hands), the ingredient can be incorporated safely into a skincare routine.
疑似致癌物（H351）： Kojic Acid carries a GHS H351 classification based on rodent thyroid follicular-cell tumour data. The SCCS evaluated this and concluded the tumour mechanism is non-genotoxic — it involves disruption of thyroid hormone homeostasis (decreased T3/T4, compensatory TSH increase, leading to thyroid cell proliferation). In vivo genotoxicity tests were negative. The SCCS noted evidence suggesting humans are less sensitive than rodents to this mechanism, but acknowledged that limited mechanistic data exists for human-specific thyroid effects of Kojic Acid. Importantly, despite this classification, the SCCS determined Kojic Acid is safe at ≤1% in cosmetics — this H351 flag is a regulatory classification, not a finding that cosmetic use is unsafe.
内分泌干扰顾虑： Kojic Acid has been shown to interfere with the hypothalamic-pituitary-thyroid (HPT) axis in rats. Re-analysis of repeated-dose studies confirmed that Kojic Acid exposure decreases serum T3/T4 levels followed by compensatory TSH release, leading to thyroid cell proliferation. The SCCS stated that whilst for some chemicals it is possible to judge thyrotoxic effects in rodents as irrelevant to humans, the mechanistic data for Kojic Acid is limited. The NOAEL based on thyroid effects was 6 mg/kg bw/day in a 28-day rat study.
浓度限制： The SCCS opinion applies specifically to use at ≤ 1% concentration for skin lightening. Products exceeding this concentration have not been assessed as safe by the SCCS. Always check the product labelling and INCI concentration if available.
皮肤屏障减弱： The SCCS specifically noted that Kojic Acid is sometimes added to peeling agents, and a weakened skin barrier may be of additional concern because of greater dermal absorption. Avoid combining Kojic Acid with strong chemical exfoliants (AHAs, BHAs) or retinoids without allowing skin recovery time.
轻微的光致刺激： The SCCS reported that Kojic Acid was found to be slightly photoirritant in animal testing, though not photosensitising. Unlike retinoids or alpha hydroxy acids, Kojic Acid does not increase systemic sun sensitivity or dramatically thin the stratum corneum. The photoirritancy is mild and manageable with daily broad-spectrum sunscreen use (SPF 30+).
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 critical when using any brightening active. Kojic Acid was found to be slightly photoirritant by the SCCS, though it does not increase sun sensitivity the way retinoids or AHAs do. UV exposure drives the very melanin production you are trying to suppress. Use broad-spectrum SPF 30+ every morning without exception.
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 specifically warned that a weakened skin barrier may increase dermal absorption of Kojic Acid. Introduce both gradually together, for example alternating on different days (e.g., Kojic Acid on Monday, AHA on Wednesday, Kojic Acid on Friday) to allow the skin barrier to recover between actives.
Both are potent tyrosinase inhibitors. Combining them may increase the risk of irritation and excessive depigmentation without proportional benefit. Hydroquinone is banned in EU cosmetics; if used in other jurisdictions, consult a dermatologist before combining.
High-concentration retinoids increase skin turnover and can compromise the barrier. Given the SCCS warning about increased absorption with weakened barriers, combining Kojic Acid with potent retinoids may increase systemic exposure. This is a precaution, not an absolute contraindication — introduce gradually and with professional guidance. Many dermatologists successfully prescribe both together at appropriate concentrations.
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%.