Pet Safety / Compounds / Cypermethrin

Is Cypermethrin safe for dogs and cats?

Low risk for pets

Dogs efficiently metabolize cypermethrin via hepatic esterases and glucuronidation; product formulations designed for dogs (flea sprays, spot-ons) are generally safe at label doses; high-dose occupational or accidental exposure can cause mild tremors and hypersalivation; cypermethrin spot-ons for large dogs applied to cats is a common tragedy.

What is cypermethrin?

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

Also known as: [cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate, Supercypermethrin, Barricade, Ripcord.

IUPAC name
[cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate
CAS number
52315-07-8
Molecular formula
C22H19Cl2NO3
Molecular weight
416.3 g/mol
SMILES
CC1(C(C1C(=O)OC(C#N)C2=CC(=CC=C2)OC3=CC=CC=C3)C=C(Cl)Cl)C
PubChem CID
2912

Risk for dogs

Low risk

Dogs efficiently metabolize cypermethrin via hepatic esterases and glucuronidation; product formulations designed for dogs (flea sprays, spot-ons) are generally safe at label doses; high-dose occupational or accidental exposure can cause mild tremors and hypersalivation; cypermethrin spot-ons for large dogs applied to cats is a common tragedy.

Risk for cats

Extreme risk

Cypermethrin is a type II alpha-cyano pyrethroid — cats are profoundly sensitive; accidental dermal exposure to cypermethrin-containing pet shampoos, flea sprays, or household sprays causes sodium channel dysfunction (hyperpolarization block) with tremors, hypersalivation, seizures, and death. Single flea-spray application intended for dogs is sufficient to cause fatal toxicosis in cats. Treatment: bathing (remove dermal residue), cyproheptadine (antagonizes serotonin co-effects), methocarbamol for tremors, thermoregulation.

Regulatory consensus

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

AgencyYearClassificationNotes
EPA CTX / EPA OPP—Group C Possible Human Carcinogen
EPA CTX / Genetox—Genotoxicity: positive (Ames: None, 1 positive / 2 negative reports)
EPA CTX / Genetox—Genotoxicity: positive (Ames: None, 1 positive / 2 negative reports)
US_EPA2024registeredEPA-registered pyrethroid.
EU_REACH2024approvedEU approved with restrictions.

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 cypermethrin

  • 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 Cypermethrin:

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: Variable; lower long-term
  • Spinosad
    Relative cost: 1.2-2×
  • Essential oil repellents
    Relative cost: 1.2-2×
  • Physical exclusion
    Relative cost: 1.2-2×

Frequently asked questions

Is cypermethrin safe for pets?

Dogs efficiently metabolize cypermethrin via hepatic esterases and glucuronidation; product formulations designed for dogs (flea sprays, spot-ons) are generally safe at label doses; high-dose occupational or accidental exposure can cause mild tremors and hypersalivation; cypermethrin spot-ons for large dogs applied to cats is a common tragedy.

What products contain cypermethrin?

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

Why do regulators disagree about cypermethrin?

Cypermethrin has been classified by 5 agencies including EPA CTX / EPA OPP, EPA CTX / Genetox, EPA CTX / Genetox, US_EPA, EU_REACH, 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 Cypermethrin in the pets app

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

Open in pets View raw API data

Sources (2)
  1. US EPA Pyrethroid Reregistration Eligibility Decision — cypermethrin/deltamethrin/lambda-cyhalothrin/bifenthrin/cyfluthrin/fenvalerate/tau-fluvalinate/fenpropathrin; type I/II classification; aquatic toxicity; cat sensitivity; sodium channel mechanism; human paresthesia; buffer zones (2011) (2011) — regulatory
  2. ASPCA Animal Poison Control Center: Pyrethroid Toxicosis in Cats and Dogs — type I vs type II CS/T syndromes; extreme cat sensitivity (sodium channel/UGT deficiency); bathing decontamination; methocarbamol tremor control; cyproheptadine; lipid emulsion severe cases (2023) (2023) — veterinary

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 →