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Methylchloroisothiazolinone
AKA “5-Chloro-2-methyl-4-isothiazolin-3-one, CMIT, 5-Chloro-2-methyl-3(2H)-isothiazolone, 5-Chloro-2-methyl-3-isothiazolone, Kathon CG 5243, 3(2H)-Isothiazolone, 5-chloro-N-methylisothiazolone, 5-chloro-2-methylisothiazolin-3-one”
Synthetic
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Ingredient Facts
Methylchloroisothiazolinone
AKA: 5-Chloro-2-methyl-4-isothiazolin-3-one, CMIT, 5-Chloro-2-methyl-3(2H)-isothiazolone, 5-Chloro-2-methyl-3-isothiazolone, Kathon CG 5243, 3(2H)-Isothiazolone, 5-chloro-N-methylisothiazolone, 5-chloro-2-methylisothiazolin-3-one
Synthetic · Preservative | Antimicrobial · EWG: 4
Plant-Derived
Preservative
Medicated Active
Synthetic
Clean
A synthetic preservative that keeps products fresh and prevents bacterial growth. May cause sensitivity in some users.
Solubility Solubility in g/100 mL solvent: water, infinite
Formula
C4H4ClNOS
Mol. Weight
149.60
CAS #
26172-55-4
Form
Liquid
Plant-Derived
Synthetic. Synthesized from isothiazole, a five-membered heterocyclic ring containing nitrogen and sulfur atoms. Produced through chlorination and methylation reactions of isothiazoline precursors under controlled chemical conditions.
Function
Preservative | Antimicrobial
Benefits
Preserves Formula
Fights Bacteria
Prevents microbial growth
Traditional Use
Synthesized in the 1970s as a broad-spectrum biocide and preservative for cosmetics and personal care products. Created to address the need for more stable and effective antimicrobial preservatives.
Skin Types
all-skin-types
Best For
Target
General
Melanin-Rich Skin
Suitable
Pregnancy Safe
Caution
Allergen Warning
⚠️ MI/MCI Preservative
Allergen Warning
⚠️ MI/MCI Preservative
EWG Score4
CIR Safety Findings
all-shades-safe, Not a Sensitizer
Regulatory Status
USA✔ permitted
EU✔ permitted
JAPAN✔ permitted
CANADA✔ permitted
Verified Feb 2026
Data: PubChem · CosIng · EWG · CIR
Methylchloroisothiazolinone — Duck Heart Ghost