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Annex V Entry 57 27/07/2020

METHYLISOTHIAZOLINONE

2-Methyl-2H-isothiazol-3-one

METHYLISOTHIAZOLINONE appears in Annex V as a positive-list preservative entry for EU cosmetics. Maximum concentration in this record: 0,0015 % Rinse-off products.

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Permitted preservative— Annex V, EU Regulation 1223/2009
Max conc.: 0,0015 % Rinse-off products
Entry: 57

Chemical identity and properties

PubChem 2D chemical structure for CAS 2682-20-4
CAS 2682-20-4PubChem CID 39800

Methylisothiazolinone

Methylisothiazolinone is a 1,2-thazole that is 4-isothiazolin-3-one bearing a methyl group on the nitrogen atom. It is a powerful biocide and preservative and is the minor active ingredient in the commercial product KathonTM. It has a role as an antimicrobial agent, an antifungal agent and an antifouling biocide. — ChEBI

IUPAC name
2-methyl-1,2-thiazol-3-one
Molecular formula
C4H5NOS
Molecular weight
115.16 g/mol
Exact mass
115.00918496 Da
XLogP3
0.0
Topological polar surface area
45.6 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
2
Covalent units
1
Defined stereocentres
0

Also known as

2-Methyl-4-isothiazolin-3-one2-Methyl-3(2H)-isothiazolone2-Methyl-4-isothiazoline-3-oneN-methylisothiazolone3(2H)-Isothiazolone, 2-methyl-2-methyl-3-isothiazolonen-methylisothiazolin-3-oneNeolone 950
16 more reported names
2-methyl-1,2-thiazol-3(2H)-one229D0E1QFA2-Methyl-4-isothiazoline-3-ketoneCHEBI:53620methyl-isothiazolinonemethylisothiazolidinoneRefChem:158243220-239-6methylisothiazolone2-methylisothiazol-3(2h)-one2-METHYL-2H-ISOTHIAZOL-3-ONEMITNeoloneN-Methyl-3-oxodihydroisothiazole2-Methyl-4-isothiazolin-3-one (MI)Kordek 50
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External database identifiers

Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Maximum concentration

0,0015 % Rinse-off products

INCI glossary name

METHYLISOTHIAZOLINONE

Chemical name

2-Methyl-2H-isothiazol-3-one

Chemical / IUPAC name

2-Methyl-2H-isothiazol-3-one

Regulatory information

Regulation

(EU) 2017/1224

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SCCS opinions

Identified ingredients

Key data

CAS
2682-20-4
EC
220-239-6
Annex
V
Entry number
57

Inventory links for METHYLISOTHIAZOLINONE

Direct matches are limited for this record, so nearby entries from Annex V are shown as well.

Annex V 52
Nearby record in the same annex

SILVER CHLORIDE

CAS: 7783-90-6
EC: 232-033-3
Annex V 50
Nearby record in the same annex

chlorphenesin

CAS: 104-29-0
EC: 203-192-6

What Annex V means for METHYLISOTHIAZOLINONE

METHYLISOTHIAZOLINONE is an approved preservative listed in Annex V of EU Cosmetics Regulation 1223/2009. Only substances on this positive list may be used as cosmetic preservatives in the EU.

Each preservative entry specifies maximum permitted concentrations and applicable product scope. Concentrations must not exceed the listed maximum. Some preservatives require warning statements on the product label.

This record is linked to 1 CosIng inventory ingredient for name and identifier cross-reference. The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Use concentration must not exceed: 0,0015 % Rinse-off products
  • Verify the preservative is effective at the permitted concentration for your matrix.

Frequently asked questions

Yes. METHYLISOTHIAZOLINONE is listed in Annex V of EU Cosmetics Regulation 1223/2009 as a permitted preservative. It may be used in cosmetics up to the maximum concentration specified above, within the permitted product scope.

CAS 2682-20-4 is the unique numerical identifier assigned to METHYLISOTHIAZOLINONE by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

The maximum concentration of 0,0015 % Rinse-off products applies to the concentration of the substance in the ready-to-use cosmetic product. When the substance is supplied as part of a blend or mixture, the calculation must account for the contribution of all sources in the formulation. The combined concentration must not exceed the stated limit.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex V record METHYLISOTHIAZOLINONE

This page summarizes one Annex V record for METHYLISOTHIAZOLINONE from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex V conditions for METHYLISOTHIAZOLINONE, but confirm any final regulatory decision against the current official annex wording and source files.

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