Pet Safety / Compounds / Resmethrin

Is Resmethrin safe for dogs and cats?

Low risk for pets

Dogs tolerate resmethrin at typical exposure concentrations from community mosquito control programs; the compound's rapid outdoor degradation further limits cumulative exposure. Direct high-dose application or ingestion of concentrate formulations would require supportive care.

What is resmethrin?

The IUPAC name is (5-benzylfuran-3-yl)methyl 2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropane-1-carboxylate.

Also known as: (5-benzylfuran-3-yl)methyl 2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropane-1-carboxylate, Benzofuroline, Chryson, Chrysron.

IUPAC name
(5-benzylfuran-3-yl)methyl 2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropane-1-carboxylate
CAS number
10453-86-8
Molecular formula
C22H26O3
Molecular weight
338.4 g/mol
SMILES
CC(=CC1C(C1(C)C)C(=O)OCC2=COC(=C2)CC3=CC=CC=C3)C
PubChem CID
5053

Risk for dogs

Low risk

Dogs tolerate resmethrin at typical exposure concentrations from community mosquito control programs; the compound's rapid outdoor degradation further limits cumulative exposure. Direct high-dose application or ingestion of concentrate formulations would require supportive care.

Risk for cats

High risk

Resmethrin is a type I pyrethroid — cats are sensitive and T-syndrome is the characteristic toxicity presentation. Community mosquito fogging programs using resmethrin (ULV aerial or truck applications) can expose outdoor cats directly; cats should be kept indoors during and for several hours after community fogging events. Indoor applications around ornamental plants or for indoor mosquito control are uncommon but represent a direct exposure risk for cats in treated spaces. Resmethrin photodegrades rapidly, which reduces outdoor environmental persistence compared to more stable pyrethroids, but acute exposure during application remains a concern.

Regulatory consensus

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

AgencyYearClassificationNotes
EPA CTX / EPA OPP—Likely to be Carcinogenic to Humans
EPA CTX / CalEPA—Known human carcinogen
EPA CTX / Genetox—Genotoxicity: negative (Ames: None, 0 positive / 2 negative reports)
EPA CTX / Genetox—Genotoxicity: negative (Ames: None, 0 positive / 2 negative reports)

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 resmethrin

  • 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 Resmethrin:

  • 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 resmethrin safe for pets?

Dogs tolerate resmethrin at typical exposure concentrations from community mosquito control programs; the compound's rapid outdoor degradation further limits cumulative exposure. Direct high-dose application or ingestion of concentrate formulations would require supportive care.

What products contain resmethrin?

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

Why do regulators disagree about resmethrin?

Resmethrin has been classified by 4 agencies including EPA CTX / EPA OPP, EPA CTX / CalEPA, EPA CTX / Genetox, 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 Resmethrin in the pets app

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

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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 →