Worth a closer look
Evidence key Strong Moderate Weak How we grade
Skin allergen Chemical of concern Restricted in the EU
- Also on labels as
- MI, MIT
- What it can be used for
- Preserves the product (the functions the EU ingredient database, CosIng, lists for it; a product may use it for any of them)
- CAS number
- 2682-20-4
Why it’s flagged
Classified as a skin sensitizer (may cause an allergic skin reaction).
- Skin Sens. 1A (H317). Source: EU CLP Regulation, Annex VI harmonized classification
EU hazard statement H317: may cause an allergic skin reaction.
Listed as a chemical of concern by the Campaign for Safe Cosmetics.
- “Methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT)”. Source: Campaign for Safe Cosmetics
The Campaign for Safe Cosmetics is an advocacy group. Its profiles explain why it considers these ingredients a concern.
Allowed in EU cosmetics only with limits.
- Annex V entry 39; rinse-off products only. Source: EU Cosmetics Regulation, Annex V (preservatives)
- Annex V entry 57; rinse-off products only. Source: EU Cosmetics Regulation, Annex V (preservatives)
Annex III (restricted substances) or Annex V (preservatives) of the EU Cosmetics Regulation sets maximum amounts, allowed product types or required warnings.
The EU allows it only in rinse-off products (like shampoo or soap), not in leave-on products (like lotion or makeup). EU rules allow this ingredient only in products you wash off. It isn't allowed in creams, lotions, makeup or other products left on the skin.
What the research says
We have no graded research on Methylisothiazolinone by name yet. About ingredients flagged like this one:
- In a survey of 187 US pediatric personal-care products, preservatives (57.8% of products) were a more common source of contact allergens than fragrance (29.4%), even though the products were being screened specifically for hypoallergenic/fragrance-related marketing claims. Moderate evidence. Hamann 2015
Each finding shows its evidence grade. See every graded fact or how we grade.
What this page can’t tell you
These lists describe what a substance can do, its hazard. The risk from one product depends on how much is in it and how you use it, and the label doesn’t say how much.
Not being on a list doesn’t make an ingredient safe. It may never have been assessed.
Check your products
Check a whole labelProducts that list itEWG Skin DeepShop fragrance-free
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Flagged the same way
Official lists checked September 2026. Spotted a mistake? Tell us.