Methylisothiazolinone (MIT) on your skin: a safety profile
Moderate risk(People-specific data is limited; this page draws from human adult context.) Methylisothiazolinone (2-methyl-4-isothiazolin-3-one; MIT; MI; CAS 2682-20-4) is an isothiazolinone biocide structurally related to methylchloroisothiazolinone (MCI) but lacking the chlorine substituent. MIT entered widespread cosmetic use primarily as a 'paraben-free' alternative preservative in the 2000s and 2010s, both in the MCI/MI (Kathon CG) combination and increasingly as a sole preservative. The widespread adoption of MIT as a sole cosmetic preservative, particularly in rinse-off products (shampoos, body washes) but also in leave-on products (creams, wipes), quickly led to recognition of MIT as an independent major cause of allergic contact dermatitis. The EU Scientific Committee on Consumer Safety (SCCS) concluded in 2014 that MIT was safe in rinse-off products at 0.0015% but unsafe at any concentration in leave-on products — a finding that led to the Commission Regulation (EU) 2016/1198 banning MIT from leave-on cosmetics effective August 2017. MIT's sensitization potency is classified as a strong sensitizer, with LLNA EC3 values typically 0.5–1%. The 'paraben scare' that drove consumers and manufacturers away from parabens in the 2000s-2010s contributed to MI's rapid rise and subsequent sensitization epidemic — illustrating the importance of evidence-based assessment of preservative alternatives. MT also has demonstrated in vitro neurotoxicity in neuronal cell culture models at concentrations above 10 ppm, though the relevance to human cosmetic exposure is debated. MIT is also used as an industrial biocide in paint, adhesives, and metalworking fluids, creating additional occupational exposure scenarios.
What is methylisothiazolinone (mit)?
The IUPAC name is 2-methyl-1,2-thiazol-3-one.
Also known as: 2-methyl-1,2-thiazol-3-one, Methylisothiazolinone, 2-Methyl-4-isothiazolin-3-one, 2-Methyl-3(2H)-isothiazolone.
- IUPAC name
- 2-methyl-1,2-thiazol-3-one
- CAS number
- 2682-20-4
- Molecular formula
- C4H5NOS
- Molecular weight
- 115.16 g/mol
- SMILES
- CN1C(=O)C=CS1
- PubChem CID
- 39800
Risk for people
Moderate riskMethylisothiazolinone (2-methyl-4-isothiazolin-3-one; MIT; MI; CAS 2682-20-4) is an isothiazolinone biocide structurally related to methylchloroisothiazolinone (MCI) but lacking the chlorine substituent. MIT entered widespread cosmetic use primarily as a 'paraben-free' alternative preservative in the 2000s and 2010s, both in the MCI/MI (Kathon CG) combination and increasingly as a sole preservative. The widespread adoption of MIT as a sole cosmetic preservative, particularly in rinse-off products (shampoos, body washes) but also in leave-on products (creams, wipes), quickly led to recognition of MIT as an independent major cause of allergic contact dermatitis. The EU Scientific Committee on Consumer Safety (SCCS) concluded in 2014 that MIT was safe in rinse-off products at 0.0015% but unsafe at any concentration in leave-on products — a finding that led to the Commission Regulation (EU) 2016/1198 banning MIT from leave-on cosmetics effective August 2017. MIT's sensitization potency is classified as a strong sensitizer, with LLNA EC3 values typically 0.5–1%. The 'paraben scare' that drove consumers and manufacturers away from parabens in the 2000s-2010s contributed to MI's rapid rise and subsequent sensitization epidemic — illustrating the importance of evidence-based assessment of preservative alternatives. MT also has demonstrated in vitro neurotoxicity in neuronal cell culture models at concentrations above 10 ppm, though the relevance to human cosmetic exposure is debated. MIT is also used as an industrial biocide in paint, adhesives, and metalworking fluids, creating additional occupational exposure scenarios.
Regulatory consensus
15 regulatory and scientific bodies have classified Methylisothiazolinone (MIT). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| US EPA | 2000 | not classifiable as to human carcinogenicity (Group D) | |
| EFSA | 2016 | not evaluated for carcinogenicity; strong contact sensitizer regulated under EU Cosmetics Regulation (EC) No 1223/2009; banned from leave-on cosmetics effective 2016 (Commission Regulation EU 2016/1198); restricted to 0.0015% (15 ppm) in rinse-off cosmetics; SCCS 2014 opinion found 15 ppm safe for rinse-off but no safe level established for leave-on applications; MI-alone sensitization epidemic coincided with shift away from MCI/MI combination | |
| EPA CTX / Genetox | — | Genotoxicity: negative (Ames: negative, 1 positive / 9 negative reports) | |
| EPA CTX / Genetox | — | Genotoxicity: negative (Ames: negative, 1 positive / 9 negative reports) | |
| EPA CTX / Skin-Eye | — | Skin Sensitization: Sh (score: high) | |
| EPA CTX / Skin-Eye | — | Skin Sensitization: SkinSens1 (score: high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Skin corrosion - category 1B (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Sensitization: Skin sensitisation - category 1 (score: high) | |
| EPA CTX / Skin-Eye | — | Eye Irritation: Category 8.3A (Category 1) (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Irritation: Category 8.2B (Category 1B) (score: very high) | |
| EPA CTX / Skin-Eye | — | Skin Sensitization: Category 6.5B (Category 1) (score: moderate) | |
| EU SCCS | — | NOT SAFE for use in leave-on cosmetics at any concentration. Safe in rinse-off products at ≤15 ppm (2013 SCCS opinion) | |
| EU CLP | — | Acute Tox 3 (oral), Acute Tox 3 (dermal), Skin Corr 1B/C, Skin Sens 1A (extremely potent sensitizer), Aquatic Acute 1, Aquatic Chronic 1 | |
| EU Cosmetics | — | Banned in leave-on cosmetics (2015). Allowed in rinse-off at ≤15 ppm (MIT alone, not combined with MCI) | |
| ACDS | — | Contact Allergen of the Year 2013 (American Contact Dermatitis Society) |
Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.
Where you encounter methylisothiazolinone (mit)
- Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
- Occupational Environments — Factories, Warehouses, Transportation vehicles
- Personal Care — shampoo, conditioner, lotion, cosmetics, sunscreen
- Personal Care (Rinse-Off) — Shampoo, Body wash, Hand soap, Conditioner
- Household Products — Laundry detergent, Dish soap, All-purpose cleaners, Wet wipes
- Paints And Coatings — Water-based paint preservative (in-can), Adhesive preservative
- Industrial — Cooling tower biocide, Metalworking fluid preservative, Paper mill slimicide
Safer alternatives
Lower-risk approaches that achieve a similar outcome to Methylisothiazolinone (MIT):
-
Physical/mechanical pest control (IPM)
Trade-offs: More labor-intensive. May not be sufficient for severe infestations.Relative cost: 1.2-2×
-
Phenoxyethanol
Relative cost: 1.2-2×
-
Organic acids (benzoic/sorbic)
Relative cost: 2-5× conventional
Frequently asked questions
What products contain methylisothiazolinone (mit)?
Methylisothiazolinone (MIT) appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); shampoo (Personal care).
Why do regulators disagree about methylisothiazolinone (mit)?
Methylisothiazolinone (MIT) has been classified by 15 agencies including US EPA, EFSA, EPA CTX / Genetox, EPA CTX / Genetox, EPA CTX / Skin-Eye, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.
See Methylisothiazolinone (MIT) in the body app
Look up products containing methylisothiazolinone (mit), compare to alternatives, and explore the full data record.
Open in body View raw API dataSources (2)
- US EPA Methylisothiazolinone: Group D Not Classifiable; FIFRA Pesticide Registration; Strong Sensitizer EC3 0.5–1%; Paraben-Free Preservative Epidemic; Wet Wipes Sensitization; In Vitro Neurotoxicity; Industrial Paint and Adhesive Biocide (2000) — regulatory
- EFSA/SCCS Methylisothiazolinone: EU Leave-On Ban Commission Regulation 2016/1198; SCCS 2014 Safety Assessment; Rinse-Off Maximum 0.0015%; Pediatric Wet Wipes Dermatitis Epidemic; Diaper Area ACD; Aquatic LC50 0.1–2 mg/L (2016) — regulatory
Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →