Baby Safety / Compounds / Methylchloroisothiazolinone (MCI/Kathon CG)

Is Methylchloroisothiazolinone (MCI/Kathon CG) safe for babies and kids?

High risk for kids

Infants are exposed to Methylchloroisothiazolinone (MCI/Kathon CG) through personal care products (lotions, wipes) and food. Immature skin barrier and hepatic metabolism increase effective dose per body weight.

What is methylchloroisothiazolinone (mci/kathon cg)?

The IUPAC name is 5-chloro-2-methyl-1,2-thiazol-3-one.

Also known as: 5-chloro-2-methyl-1,2-thiazol-3-one, 5-Chloro-2-methyl-4-isothiazolin-3-one, Methylchloroisothiazolinone, CMIT.

IUPAC name: 5-chloro-2-methyl-1,2-thiazol-3-one
CAS number: 26172-55-4
Molecular formula: C4H4ClNOS
Molecular weight: 149.6 g/mol
SMILES: CN1C(=O)C=C(S1)Cl
PubChem CID: 33344

Risk for babies

High risk

Neonates and infants up to 12 months have incomplete blood-brain barrier development, immature Phase I/II metabolic enzymes (particularly CYP3A4, UGT1A1), and higher gastrointestinal permeability. Equivalent doses produce higher internal concentrations and longer residence times.

What to do: Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Risk for pregnant and nursing people

Context-dependent

Prenatal exposure to Methylchloroisothiazolinone (MCI/Kathon CG) through personal care products and food is a concern. Some preservatives (parabens) exhibit weak estrogenic activity that may affect fetal endocrine development.

No specific reproductive toxicity data identified, but pregnancy-specific safety data is limited for most chemicals. Precautionary minimization of exposure is recommended.

What to do: Minimize exposure during pregnancy and lactation. Consult healthcare provider regarding specific risks. Consider alternative products with lower hazard profiles.

Regulatory consensus

11 regulatory and scientific bodies have classified Methylchloroisothiazolinone (MCI/Kathon CG). The classifications differ — that's the data.

Agency	Year	Classification
US EPA	2000	not classifiable as to human carcinogenicity (Group D)
EFSA	2014	not evaluated for carcinogenicity; regulated as potent contact sensitizer under EU Cosmetics Regulation (EC) No 1223/2009; banned from leave-on cosmetics (2014 Commission Decision); restricted to 0.0015% in rinse-off cosmetics; SCCS 2014 opinion found no safe concentration can be established for use in leave-on products due to sensitization epidemic
EPA CTX / Genetox	—	Genotoxicity: negative (single report) (Ames: None, 0 positive / 1 negative reports)
EPA CTX / Genetox	—	Genotoxicity: negative (single report) (Ames: None, 0 positive / 1 negative reports)
EPA CTX / Skin-Eye	—	Skin Sensitization: Sh (score: high)
EPA CTX / Skin-Eye	—	Skin Sensitization: SkinSens1 (score: high)
EPA CTX / Skin-Eye	—	Skin Irritation: Skin corrosion - category 1B (score: very high)
EPA CTX / Skin-Eye	—	Skin Sensitization: Skin sensitisation - category 1 (score: high)
EPA CTX / Skin-Eye	—	Eye Irritation: Category 8.3A (Category 1) (score: very high)
EPA CTX / Skin-Eye	—	Skin Irritation: Category 8.2B (Category 1B) (score: very high)
EPA CTX / Skin-Eye	—	Skin Sensitization: Category 6.5B (Category 1) (score: moderate)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where kids encounter methylchloroisothiazolinone (mci/kathon cg)

Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
Occupational Environments — Factories, Warehouses, Transportation vehicles
Personal Care — shampoo, conditioner, lotion, cosmetics, sunscreen

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Methylchloroisothiazolinone (MCI/Kathon CG):

Physical/mechanical pest control (IPM)
Trade-offs: More labor-intensive. May not be sufficient for severe infestations.

Relative cost: 1.2-2×
Phenoxyethanol
Relative cost: 1.2-2×
Benzisothiazolinone (BIT) at lower concentration
Relative cost: 1.2-2×

Frequently asked questions

Is methylchloroisothiazolinone (mci/kathon cg) safe for kids?

What products contain methylchloroisothiazolinone (mci/kathon cg)?

Methylchloroisothiazolinone (MCI/Kathon CG) appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); shampoo (Personal care).

What should I do if my child is exposed to methylchloroisothiazolinone (mci/kathon cg)?

Minimize infant exposure through source control. For breastfeeding mothers: reduce maternal exposure. For formula-fed infants: use certified low-migration bottles and verified water sources. Consult pediatrician regarding any concerns.

Why do regulators disagree about methylchloroisothiazolinone (mci/kathon cg)?

Methylchloroisothiazolinone (MCI/Kathon CG) has been classified by 11 agencies including US EPA, EFSA, EPA CTX / Genetox, EPA CTX / Genetox, EPA CTX / Skin-Eye, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Methylchloroisothiazolinone (MCI/Kathon CG) in the baby app

Look up products containing methylchloroisothiazolinone (mci/kathon cg), compare to alternatives, and explore the full data record.

Open in baby View raw API data

Sources (2)

US EPA Methylchloroisothiazolinone: Group D Not Classifiable; FIFRA Registered Antimicrobial Pesticide; Extreme Skin Sensitizer EC3 ~0.002%; Kathon CG Industrial Biocide; Aquatic LC50 0.1–1 mg/L; Algal EC50 0.02–0.05 mg/L (2000) — regulatory
EFSA/SCCS MCI/Kathon CG: EU Leave-On Cosmetics Ban 2015; Rinse-Off Maximum 0.0015%; Contact Sensitization Epidemic Europe 1980s–2010s; LLNA Extreme Sensitizer; Sensitization Rate Reversal Post-Restriction; Wet Wipes MI Cross-Reaction (2014) — regulatory

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →