Pet Safety / Compounds / Esfenvalerate

Is Esfenvalerate safe for dogs and cats?

Low risk for pets

Dogs are not significantly affected by esfenvalerate at agricultural use concentrations; livestock species (cattle, horses, poultry) are also relatively tolerant; no specific veterinary warnings distinct from the class.

What is esfenvalerate?

The IUPAC name is [(S)-cyano-(3-phenoxyphenyl)methyl] (2S)-2-(4-chlorophenyl)-3-methylbutanoate.

Also known as: [(S)-cyano-(3-phenoxyphenyl)methyl] (2S)-2-(4-chlorophenyl)-3-methylbutanoate, Asana, Fenvalerate alpha, Halmark.

IUPAC name
[(S)-cyano-(3-phenoxyphenyl)methyl] (2S)-2-(4-chlorophenyl)-3-methylbutanoate
CAS number
66230-04-4
Molecular formula
C25H22ClNO3
Molecular weight
419.9 g/mol
SMILES
CC(C)C(C1=CC=C(C=C1)Cl)C(=O)OC(C#N)C2=CC(=CC=C2)OC3=CC=CC=C3
PubChem CID
10342051

Risk for dogs

Low risk

Dogs are not significantly affected by esfenvalerate at agricultural use concentrations; livestock species (cattle, horses, poultry) are also relatively tolerant; no specific veterinary warnings distinct from the class.

Risk for cats

Extreme risk

Esfenvalerate is the active S-alpha enantiomer of racemic fenvalerate — it has the same type II pyrethroid mechanism and extreme feline toxicity; being the purified active isomer, lower mass exposure is required compared to racemic fenvalerate to cause equivalent toxicity. Agricultural applications around barns, grain storage, and farm buildings create cat exposure risk in rural settings. Esfenvalerate-treated crops (Asana XL) represent a potential source of indirect exposure through contaminated soil, water, or prey species.

Regulatory consensus

1 regulatory bodyhas classified Esfenvalerate.

AgencyYearClassificationNotes
EPA CTX / EPA OPP—Group E Evidence of Non-carcinogenicity for Humans

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 esfenvalerate

  • 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 Esfenvalerate:

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: 1.2-2×

Frequently asked questions

Is esfenvalerate safe for pets?

Dogs are not significantly affected by esfenvalerate at agricultural use concentrations; livestock species (cattle, horses, poultry) are also relatively tolerant; no specific veterinary warnings distinct from the class.

What products contain esfenvalerate?

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

See Esfenvalerate in the pets app

Look up products containing esfenvalerate, 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 →