Methylisothiazolinone
INCI: METHYLISOTHIAZOLINONE
Regulatory Status
For full compliance data across 55 jurisdictions, use the Substance Compliance tool.
Safety Data
Calculate MoS for your specific formulation with the MoS Calculator.
Toxicological Studies
6 study endpoints found for Methylisothiazolinone. 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 |
|---|---|---|---|---|---|
| LOAEL | 75 ppm | oral | rat | Subchronic | COSMOS_DB |
| NOAEL | 19 mg/kg bw/day | oral | rat | oral | REACH |
| NOAEL | 28.6 mg/kg bw/day | oral | rat | oral | REACH |
| NOAEL | 30.09 mg/kg bw/day | oral | rat | oral | REACH |
| NOAEL | 40.6 mg/kg bw/day | oral | dog | oral | REACH |
| NOEL | 30 ppm | oral | rat | oral | REACH |
Safety Opinions
Official safety assessments from the Scientific Committee on Consumer Safety (SCCS) and Cosmetic Ingredient Review (CIR).
Sensitization Profile
Contact sensitization data for Methylisothiazolinone based on clinical patch test studies and IFRA standards.
Source: NACDG 2021-22; ESSCA 2019/20
Expert Verdict
HIGH CONCERN — contraindicated for sensitive-skin formulations. Methylisothiazolinone triggered a documented epidemic of contact allergy in Europe in the 2010s with sensitization rates of 6–12% in dermatitis populations. EU banned from all leave-on cosmetics in 2016; still permitted in rinse-off at ≤0.0015% only. Remains permitted in leave-on products in US, Canada, and Australia — formulators should avoid in all leave-on applications globally regardless of local regulation. Sensitization rate for phenoxyethanol (preferred alternative) is 0.3–1% — 6–40x lower. Avoiding MI in leave-on products reduces both individual sensitization risk and population-level allergen burden.
Regulatory Flags
Frequently Asked Questions
Is Methylisothiazolinone safe in cosmetics?
HIGH CONCERN — contraindicated for sensitive-skin formulations. Methylisothiazolinone triggered a documented epidemic of contact allergy in Europe in the 2010s with sensitization rates of 6–12% in dermatitis populations. EU banned from all leave-on cosmetics in 2016; still permitted in rinse-off at ≤0.0015% only. Remains permitted in leave-on products in US, Canada, and Australia — formulators should avoid in all leave-on applications globally regardless of local regulation. Sensitization rate for phenoxyethanol (preferred alternative) is 0.3–1% — 6–40x lower. Avoiding MI in leave-on products reduces both individual sensitization risk and population-level allergen burden. The EU classifies Methylisothiazolinone as "restricted". Safety rating: POOR. 6 toxicological study endpoint(s) are available in our database. This ingredient has been reviewed by cir.
Is Methylisothiazolinone allowed in the EU?
Methylisothiazolinone EU regulatory status: restricted. Maximum allowed concentration: 0.0015% in rinse-off cosmetics only; banned in all leave-on cosmetics. This is based on EU Regulation 1223/2009 and its amendments.
What does Methylisothiazolinone do in cosmetics?
Methylisothiazolinone functions as: preservative. It is classified as a Preservative in our database. CAS number: 2682-20-4.
What is the Margin of Safety for Methylisothiazolinone?
not established The Margin of Safety (MoS) is calculated using SCCS methodology. A MoS above 100 is generally considered safe. Use the MoS Calculator tool to calculate MoS for your specific formulation and product category.
What is the NOAEL for Methylisothiazolinone?
The NOAEL (No Observed Adverse Effect Level) for Methylisothiazolinone is 75 ppm based on a Subchronic study via oral route in rat. A total of 6 study endpoints are available. Source: COSMOS_DB.
Compliance Tools
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