murphyMethylisothiazolinone
AKA: 2682-20-4, 2-Methyl-4-isothiazolin-3-one, 2-Methyl-3(2H)-isothiazolone, 2-Methyl-4-isothiazoline-3-one, N-methylisothiazolone, 3(2H)-Isothiazolone, 2-methyl-3-isothiazolone, N-methylisothiazolin-3-one, Neolone 950
Synthetic
Preservative
Not Clean
OriginDerived from isothiazole, a five-membered heterocyclic compound containing nitrogen and sulfur atoms. Synthesized through chemical reaction of methylamine and isothiazole precursors under controlled conditions.
The Expert Panel for Cosmetic Ingredient Safety concluded that Methylisothiazolinone is safe for use in rinse-off cosmetic products at concentrations up to 100 ppm (i.e. 0.01%) and safe in leave-on cosmetic products when they are formulated to be non-sensitizing, which may be determined based on a QRA or similar methodology.
Solubility Solubility in: acetonitrile 78.6; methanol 79.1; hexane 2.371; xylenol 15.65 (g/100 mL)
Formula
C4H5NOS
Mol. Weight
115.16
CAS #
2682-20-4
Form
Liquid
State
NKRA; Liquid
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Caution
Allergen Warning
⚠️ MI/MCI Preservative
Functions
Preservative
Keeps your product from growing bacteria, mold, or yeast. Without these, that jar of cream becomes a petri dish in about a week.
Preserves Formula
Prevents microbial growth
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
EWG
7
CIR
Safe as used
Pregnancy
Caution
Restricted By
CIR Safety Findings
Mixed Phototoxicity Results
Both phototoxic and non-phototoxic results in the CIR safety assessment (CIR 486 and 787 and 821)
Mixed Eye Irritation Results
8 studies / 1 irritating / 2 mixed / 5 not irritating / reactions mild to corrosive (CIR 486 and 787 and 821)
Mixed Skin Irritation Results
16 studies / 4 irritating / 4 mixed / 8 not irritating / reactions slight to corrosive (CIR 486 and 787 and 821)
Mixed Sensitization Results
22 studies / 13 sensitizing / 2 mixed / 7 not sensitizing / plus 21 case reports (CIR 114 and 486 and 646 and 787 and 821)
Dermal Absorption 8.98–54.7%
9 results from in vitro tests in the CIR safety assessment (CIR 486)
Concentration Guide
0%50%100%
Reg. limit 0.01%
EU regulatory limit: 0.01%. Source: EU Cosmetics Regulation (EC) 1223/2009, Annex V (Preservatives), Entry 57.
Regulatory Agencies
🧂Conflict of interest.
Verified Jun 2026 · 🧪 = conflict
Data: PubChem · CosIng · EWG · CIR