Also known as: BRN 1210149, EINECS 247-500-7, UNII-DEL7T5QRPN, 2,3-dihydro-2-methyl-3-oxo-5-chloroisothiazole, CMIT (+2 more)
INCI: METHYLCHLOROISOTHIAZOLINONE
Methylchloroisothiazolinone (CAS 26172-55-4) is a cosmetic preservative functioning as Preservative. Reported NOAEL =0.00038 mg/kg bw in human (SCCS Opinion); EU Regulation 1223/2009 status: restricted, max 0.0015% in rinse-off cosmetics only as MCI/MI 3:1 blend; prohibited in leave-on cosmetics; 3 safety opinions reviewed (CIR Safety Assessment). Industrial safety data is also available in the chemical safety database. Same-CAS public records also appear in pharmaceutical data.
View industrial chemical safety profile for CAS 26172-55-4 →
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Margin of Safety, dermal absorption, and sensitization profile summaries for Methylchloroisothiazolinone.
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10 study endpoints found for Methylchloroisothiazolinone. NOAEL (No Observed Adverse Effect Level) values are used to calculate the Margin of Safety per SCCS methodology.
| Endpoint | Value | Route | Species | Study Type | Source |
|---|---|---|---|---|---|
| NOAEL | =0.00038 mg/kg bw | dermal | human | reproductive toxicity | SCCS Opinion |
| NOAEL | =0.00038 mg/kg bw | dermal | human | reproductive toxicity | SCCS Opinion |
| NOAEL | =0.00038 mg/kg bw | dermal | human | reproductive toxicity | SCCS Opinion |
| NOAEL | =0.00038 mg/kg bw | dermal | human | reproductive toxicity | SCCS Opinion |
| NOAEL | =2.6 mg/kg/day | oral | rat | repeated dose toxicity | SCCS Opinion |
| NOAEL | =2.6 mg/kg/day | oral | rat | repeated dose toxicity | SCCS Opinion |
| NOAEL | =2.6 mg/kg/day | oral | rat | repeated dose toxicity | SCCS Opinion |
| NOAEL | =2.6 mg/kg/day | oral | rat | repeated dose toxicity | SCCS Opinion |
| NOAEL | =19.6 mg/kg bw | oral | rat | reproductive toxicity | SCCS Opinion |
| NOAEL | =19.6 mg/kg bw | oral | rat | reproductive toxicity | SCCS Opinion |
Official safety assessments from the Scientific Committee on Consumer Safety (SCCS) and Cosmetic Ingredient Review (CIR).
A margin-of-safety result previously shown for Methylchloroisothiazolinone has been withdrawn pending re-verification. We don't display safety verdicts we can't fully substantiate from the primary SCCS source — so this entry is being re-checked rather than shown unverified.
10 toxicity values from EPA ToxValDB (aggregated from CCTE, HPV, ToxRefDB, IRIS, and other regulatory dossiers).
| Endpoint | Value | Species | Route | Duration | Source |
|---|---|---|---|---|---|
| LEL | =4.4 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LEL | =2.8 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LEL | =5.5 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LEL | =4.3 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LEL | >39.1 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LOAEL | =11.8 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LOAEL | =8.5 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LOAEL | =16 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LOAEL | =13.4 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
| LOAEL | >39.1 mg/kg-day | Rat | oral | chronic (developmental) | EPA ToxRefDB |
Adverse Outcome Pathway data across 5 assays (DPRA, KeratinoSens, hCLAT, LLNA, NESIL) aggregated from public sources.
Source: DPRA: Urbisch et al. 2015 [DOI:10.1016/j.yrtph.2014.12.008]; KS: Urbisch et al. 2015 [DOI:10.1016/j.yrtph.2014.12.008]
Cross-referenced EDC classifications, mechanism data, and dose-response evidence from EDLists, SIN List, and cosmetic-specific detail sources.
indirect modulator
| Endpoint | Target | Value | Direction |
|---|---|---|---|
| Thyroid hormone levels (T3/T4 ↓); developmental toxicity | Thyroid axis (indirect, via oxidative stress) | EC50/IC50: LOEC ≈ 0.3 µg/L (coagulation / hatching delay; thyroid at ≥30 µg/L); LOEC: 0.3 µg/L (developmental); 30 µg/L (thyroid); NOEC: not established mixed | thyroid disruptor |
| ER/AR receptor activity | ERα / AR | EC50/IC50: No significant ER/AR activity reported; LOEC: not established; NOEC: not established mixed | not active at sub-cytotoxic concentrations |
| E2 and T changes | Steroidogenesis | EC50/IC50: LOEC ≈ 0.3 µg/L; EC50 not calculated (overlaps with cytotoxicity); LOEC: 0.3 µg/L; NOEC: not established mixed | active (similar activity to MIT but higher cytotoxicity) |
Additional regulatory detail beyond the 7-jurisdiction summary: Saudi SFDA, Korea MFDS, ASEAN ACD, Japan/Korea, Brazil/India, and cross-jurisdictional restriction entries.
| Jurisdiction | Status | Max % | Product Type |
|---|---|---|---|
| CN | permitted_preservative | 0.0015 | Rinse-off products only |
| IN | permitted_preservative | 0.0015 | all cosmetics |
| AU | restricted | - | preservatives |
Cross-database dermal penetration: EPA Dryad physics-based, Roberts Mendeley permeation, and SCCS-aggregated measured values.
| Type | DA % | Method | Skin Model | SCCS Ref |
|---|---|---|---|---|
| measured | 100.0% | - | - | SCCS/0009 |
| measured | 36.2% | - | - | SCCS/0009 |
| measured | 84.5% | - | - | SCCS/0009 |
| measured | 58.7% | - | - | SCCS/0009 |
| measured | 46.6% | - | - | SCCS/0009 |
Reported concentration ranges per product category from SCCS/CIR/industry sources.
| Product Category | Typical Range | Max Reported | Source |
|---|---|---|---|
| Shampoo | <0.0015 | 0.0015 | CIR Safety Assessment |
Preliminary editorial summary for Methylchloroisothiazolinone — not a computed safety verdict. See the sourced toxicological data above.
Public NOAEL study rows linked to Methylchloroisothiazolinone by CAS number or substance name.
Units vary across source rows: mg/kg bw, mg/kg/day
| Absorption % | Method | Vehicle |
|---|---|---|
| 100.0% | - | - |
| 36.2% | - | - |
| 84.5% | - | - |
| 58.7% | - | - |
| 46.6% | - | - |
Same-CAS public records found in pharmaceutical data.
Same-CAS rows from the pharmaceutical spoke database.
Methylchloroisothiazolinone has a safety rating of "POOR" in our database. EU status: restricted. US status: permitted. 10 toxicological study endpoint(s) are available in our database. This ingredient has been reviewed by CIR Safety Assessment.
Methylchloroisothiazolinone EU regulatory status: restricted. Maximum allowed concentration: 0.0015% in rinse-off cosmetics only as MCI/MI 3:1 blend; prohibited in leave-on cosmetics. This is based on EU Regulation 1223/2009 and its amendments.
Methylchloroisothiazolinone functions as: Preservative. It is classified as a Preservative in our database. CAS number: 26172-55-4.
The NOAEL (No Observed Adverse Effect Level) for Methylchloroisothiazolinone is =0.00038 mg/kg bw based on a reproductive toxicity study via dermal route in human. A total of 10 study endpoints are available. Source: SCCS Opinion.
Methylchloroisothiazolinone also appears in pharmaceutical data. The cross-vertical cards on this page render same-CAS public rows from the matched databases.
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