Pet Safety / Compounds / MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1)

Is MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1) safe for dogs and cats?

Moderate risk for pets

Kathon in pet shampoos can sensitize. Contact dermatitis in pets documented.

What is mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1)?

Molecular formula
Mixture 3:1 MCI:MI

Risk for dogs

Moderate risk

Kathon in pet shampoos can sensitize. Contact dermatitis in pets documented.

Risk for cats

Moderate risk

Same concern as dogs.

Regulatory consensus

4 regulatory and scientific bodies have classified MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1). The classifications differ — that's the data.

AgencyYearClassificationNotes
EU Cosmetics—Allowed in rinse-off cosmetics at ≤15 ppm (MCI/MI combined). Banned in leave-on cosmetics
EU CLP—MCI: Acute Tox 2 (oral/dermal), Skin Corr 1B, Skin Sens 1A, Aquatic Acute 1, Aquatic Chronic 1
EU BPR—Approved active substance for multiple product types under BPR 528/2012
FDA—No specific cosmetic regulation — manufacturer responsibility under FDCA. CIR reviewed as safe at ≤15 ppm in rinse-off

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 pets encounter mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1)

  • Personal Care — Shampoo (rinse-off only in EU), Body wash, Hand soap, Liquid soap
  • Household Products — Dish soap, Laundry detergent, Fabric softener, All-purpose cleaners
  • Paint And Coatings — Water-based latex paint (in-can preservative), Joint compound, Caulk and sealant
  • Industrial — Cooling tower biocide (Kathon WT), Paper mill slimicide (Kathon LX), Metalworking fluid preservative

Safer alternatives

Lower-risk approaches that achieve a similar outcome to MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1):

  • Phenoxyethanol
    Trade-offs: Most common MIT/MCI replacement in personal care. Effective against Gram-negative bacteria, weaker on fungi. No contact sensitization at use levels. Cost neutral.
    Relative cost: 1.2-2×
  • Benzisothiazolinone (BIT)
    Trade-offs: Isothiazolinone but much lower sensitization than MCI/MI. Used in paints and coatings at 50-500 ppm. Less effective in personal care. Cost: 1.5x MCI/MI.
    Relative cost: 1.2-2×
  • Silver ion technology (AgION, Biomaster)
    Trade-offs: Inorganic antimicrobial for coatings and plastics. Very long-lasting (product lifetime). No sensitization risk. Cost: 5-10x MCI/MI per unit. Environmental concerns re: aquatic silver toxicity.
    Relative cost: 1.2-2×
  • DMDM hydantoin
    Trade-offs: Formaldehyde-releaser — effective broad-spectrum but controversial. Consumer backlash ('clean beauty' exclusion). Being phased out by major brands. Cost: cheapest option.
    Relative cost: 1.2-2×

Frequently asked questions

Is mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1) safe for pets?

Kathon in pet shampoos can sensitize. Contact dermatitis in pets documented.

What products contain mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1)?

MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1) appears in: Shampoo (rinse-off only in EU) (Personal care); Body wash (Personal care); Dish soap (Household products); Laundry detergent (Household products); Water-based latex paint (in-can preservative) (Paint and coatings).

Why do regulators disagree about mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1)?

MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1) has been classified by 4 agencies including EU Cosmetics, EU CLP, EU BPR, FDA, 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 MCI/MI (Kathon CG / methylchloroisothiazolinone + methylisothiazolinone 3:1) in the pets app

Look up products containing mci/mi (kathon cg / methylchloroisothiazolinone + methylisothiazolinone 3:1), compare to alternatives, and explore the full data record.

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Sources (1)
  1. — expert_curation

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 →