Pet Safety / Compounds / Permethrin

Is Permethrin safe for dogs and cats?

Low risk for pets

Dogs metabolize pyrethroids efficiently via CYP450; permethrin spot-on products are approved for dogs. Mild transient paresthesia possible at application site; systemic toxicity rare at label doses.

What is permethrin?

The IUPAC name is (3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate.

Also known as: (3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate, Pounce, Permethrine, Permetrina.

IUPAC name
(3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate
CAS number
52645-53-1
Molecular formula
C21H20Cl2O3
Molecular weight
391.3 g/mol
SMILES
CC1(C(C1C(=O)OCC2=CC(=CC=C2)OC3=CC=CC=C3)C=C(Cl)Cl)C
PubChem CID
40326

Risk for dogs

Low risk

Dogs metabolize pyrethroids efficiently via CYP450; permethrin spot-on products are approved for dogs. Mild transient paresthesia possible at application site; systemic toxicity rare at label doses.

Risk for cats

Extreme risk

Cats lack CYP450 enzymes to metabolize pyrethroids; sodium channel dysfunction causes tremors, hypersalivation, seizures, and death. Single spot-on dog flea product exposure is frequently fatal. Immediate veterinary care required.

Regulatory consensus

16 regulatory and scientific bodies have classified Permethrin. The classifications differ — that's the data.

AgencyYearClassificationNotes
IARC—Group 3 (not classifiable)
US EPA—not classified as carcinogenic
EPA CTX / IARC—Group 3 - Not classifiable as to its carcinogenicity to humans
EPA CTX / EPA OPP—Likely to be Carcinogenic to Humans
EPA CTX / Genetox—Genotoxicity: negative (Ames: None, 0 positive / 2 negative reports)
EPA CTX / Genetox—Genotoxicity: negative (Ames: None, 0 positive / 2 negative reports)
EPA CTX / Skin-Eye—Skin Sensitization: Skin Sens. 1 (score: high)
EPA CTX / Skin-Eye—Eye Irritation: Not classified (score: low)
EPA CTX / Skin-Eye—Skin Irritation: Not classified (score: low)
EPA CTX / Skin-Eye—Skin Sensitization: Not classified (score: low)
EPA CTX / Skin-Eye—Eye Irritation: Category 6.4A (Category 2A) (score: high)
EPA CTX / Skin-Eye—Skin Irritation: Category 6.3B (Category 3) (score: moderate)
EPA CTX / Skin-Eye—Skin Sensitization: Category 6.5B (Category 1) (score: moderate)
US_EPA2024registeredEPA-registered insecticide.
IARC1991Group_3Not classifiable
EU_REACH2024approvedEU approved as biocide.

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 permethrin

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Permethrin:

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: 1.2-2×
  • Spinosad (clothing)
    Relative cost: 1.2-2×
  • DEET/Picaridin (repellent)
    Relative cost: 1.2-2×
  • Physical barriers
    Relative cost: 1.2-2×
  • Dimethicone (lice)
    Relative cost: 1.2-2×

Frequently asked questions

Is permethrin safe for pets?

Dogs metabolize pyrethroids efficiently via CYP450; permethrin spot-on products are approved for dogs. Mild transient paresthesia possible at application site; systemic toxicity rare at label doses.

What products contain permethrin?

Permethrin appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments).

Why do regulators disagree about permethrin?

Permethrin has been classified by 16 agencies including IARC, US EPA, EPA CTX / IARC, EPA CTX / EPA OPP, EPA CTX / Genetox, 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 Permethrin in the pets app

Look up products containing permethrin, compare to alternatives, and explore the full data record.

Open in pets View raw API data

Sources (3)
  1. EPA: Permethrin Reregistration Eligibility Decision (RED) (2006) — regulatory
  2. ASPCA Animal Poison Control Center: Permethrin Toxicity in Cats (2021) — report
  3. Volmer PA: Pyrethrin and pyrethroid insecticide toxicosis. Vet Clin North Am Small Anim Pract 34(2):459–465 (2004) — journal

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 →