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Methylisothiazolinone

CAS 125794-71-0 · 20/100 · High conf.

Also registered as 5 other CAS numbers

184720-17-0 · 1610617-47-4 · 2682-20-4 · 26172-55-4 · 55965-84-9

Methylisothiazolinone chemical structure

Concern score

20/100Minor concern based on regulatory listings.
High confidence

Methylisothiazolinone in plain language

What it is

On cosmetic ingredient lists it appears as “Methylchloroisothiazolinone”.

Also known as Methylchloroisothiazolinone · Methylchloroisothiazolinone and methylisothiazolinone · 2-Methyl-2H-isothiazol-3-one · 2-Methyl-3(2H)-isothiazolone · 2-Methyl-4-isothiazolin-3-one · 2-Methyl-1,2-thiazol-3(2H)-one

Show all 28 names

2-methyl-1,2-thiazol-3-one · MIT · 2-METHYL-3(2H)-ISOTHIAZOLINONE · 2-METHYL-4-ISOTHIAZOLINE-3-ONE · 2-Methyl-2H-isothiazol-3-on · 2-Methyl-3-isothiazolone · 2-Methyl-4-isothiazoline-3-ketone · 2-methyl-2H-isothiazole-3-one · 2-methyl-4-isothiazolin-3-1 · 2-methyl-4-isothiazolin-3-1%: 0.0001-0.001 · 2-methyl-4-isothiazolin-3-one %:1 ppm · 2-methylisothiazol-3(2h)-one · 3(2H)-Isothiazolone, 2-methyl- · 3(2H)-Isothiazolone, methyl- · 5-Chloro-2-methyl-2H-isothiazol-3-one · N-methylisothiazolone · Neolone 950 · kathon (2-methyl-4-isothiazolin-3-one) · methyl-isothiazolinone · methylisothiazolidinone · methylisothiazolone · n-methylisothiazolin-3-one

What it does

Used in cosmetics as a preservative. Methylchloroisothiazolinone is the heterocyclic organic compound.

  • Preservative
  • Antioxidant
  • Fragrance
  • Antimicrobial
Is it a concern?
Minor concern: no hazard classifications on record. It is listed for cosmetic use in the EU.

What the listings say

Permitted, with conditions — Methylisothiazolinone appears on published "allowed" regulatory lists rather than on a restriction list.

Mixture of 5-Chloro-2-methyl-isothiazol-3(2H)-one and 2-Methylisothiazol-3(2H)-one with magnesium chloride and magnesium nitrate is listed in Annex V of the EU Cosmetics Regulation (EC) 1223/2009 (preservatives allowed in cosmetic products).

The score describes this ingredient's chemical identity — its hazard profile from published classifications and regulatory status — not the safety of any product it appears in.

Regulation

No restrictions found. Methylisothiazolinone appears in these published regulatory listings.

  • EU Annex V — permitted preservative
  • EU permitted preservative
  • In marketed US drugs

Recorded in these product areas

  • Found in consumer products
  • Beauty
  • Cleaning
  • Pharma
  • Food
  • Industrial
  • EUCosIngActive2 entries
    • Methylchloroisothiazolinone is the heterocyclic organic compound that conforms to the formula: Restriction: V/39Source →
    • Cosmetics Regulation annex V / ref 39.Source →
  • EUECallowed_listed2 entries
    • Annex V of EU Cosmetics Regulation (EC) 1223/2009: preservatives allowed in cosmetic products. Product types: Rinse-off Maximum concentration: 0.0015% (of a mixture in the ratio 3:1 of 5-Chloro-2-methyl-isothiazol-3(2H)-one and 2-Methylisothiazol-3(2H)-oneSource →
    • Annex V of EU Cosmetics Regulation (EC) 1223/2009: preservatives allowed in cosmetic products. Maximum concentration: 0,0015 % Rinse-off productsSource →
  • EUEFSAEFSA opinionScientific Opinion of the Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) on a request related to a 16th list of substances for food contact materials (EFSA AFC)
    • Scientific Opinion of the Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) on a request related to a 16th list of substances for food contact materials (EFSA AFC)Source →
  • USEPAcommercial use observedEPA CPDat observed this chemical in 9337 composition records across product categories including Construction and building materials, Laboratory supplies, Cleaning and safety. EPA CPDat classifies this chemical for functional uses including Preservative, Antioxidant, Processing aids not otherwise specified.
    • EPA CPDat observed this chemical in 9337 composition records across product categories including Construction and building materials, Laboratory supplies, Cleaning and safety. EPA CPDat classifies this chemical for functional uses including Preservative, Antioxidant, Processing aids not otherwise specified.Source →
  • USFDAmarketed drug occurrenceFDA NDC lists this ingredient in 1 drug products and 1 package presentations.
    • FDA NDC lists this ingredient in 1 drug products and 1 package presentations.Source →
  • USFDAlisted in openFDA substanceopenFDA substance registry classifies this ingredient as chemical.
    • openFDA substance registry classifies this ingredient as chemical.Source →

Expert safety opinions

Independent scientific assessments cited by the records we hold, with the year and link where the record gives one.

  • SCCS

    EU Scientific Committee on Consumer Safety

    No SCCS opinion on file.

  • CIR

    Cosmetic Ingredient Review (US expert panel)

    No CIR safety assessment on file.

  • EFSA

    European Food Safety Authority

    • Scientific Opinion of the Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) on a request related to a 16th list of substances for food contact materials (EFSA AFC)

      2007 · EU EFSA listing · Read the source →

Evidence & sources

No graded research studies for Methylisothiazolinone yet. This record is compiled from the published data sources below — registries and regulatory listings, not study findings.

9 data sources

Where this comes from

  • CosIng

    regulatory · updated 2026-09-23

    Open →

  • EU CosIng Cosmetics Regulation Annexes

    regulatory · updated 2022-09-28

    Open →

  • EFSA OpenFoodTox

    regulatory · updated 2026-10-04

    Open →

  • EPA Chemical and Products Database

    exposure · updated september 6, 2012

    Open →

  • EPA DSSTox Identifiers

    chemistry · updated 2025-12-29

    Open →

  • FDA National Drug Code Directory

    regulatory · updated 2028-02-03

    Open →

  • FDA GSRS UNII

    registry · updated 2026-02-26

    Open →

  • openFDA Substance

    registry · updated 2026-05-24

    Open →

  • PubChem Live Enrichment

    chemistry · updated 2026-05-17

    Open →

Suitability

Context-specific fit derived from published classifications and the current ingredient evidence profile.

Food use

Food-use source coverage is present in the current record.

Good fit

The ingredient appears in food-oriented source coverage or allowed-use references, which makes food use easier to support than a context with no domain signal at all.

Fragrance avoidance

Not a strong fit for fragrance avoidance because it carries Fragrance.

Avoid

The ingredient itself is a fragrance-linked signal, so it is better treated as an avoid case when fragrance exposure is the main concern.

Where it has been recorded

How often EPA CPDat has listed Methylisothiazolinone in a product composition. These are source records, not Greenveil catalog products.

Source records

9,337

Named organisations

6

Construction and building materialsLaboratory suppliesCleaning and safetyRaw materialsHome maintenanceIndustrial products

Typical roles

PreservativeAntioxidantFragranceAntimicrobial
See products using Methylisothiazolinone →

Catalog

Found in these products

Their ingredient lists include Methylisothiazolinone; each product's own rating depends on its whole formula, so it is shown on the product page, not here.

See all 1000+ →Find products without it →

Co-occurrence

Often appears with

Ingredients that frequently appear alongside Methylisothiazolinone in the catalog.