Pyrethrins & Pyrethroids

Pyrethrins & Pyrethroids


Alternate names

pyrethroids, Chrysanthemum, flea and tick topical spot-on medications, bifenthrin, permethrin, allethrin, tetramethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin

Toxicity to pets

Pyrethrins are a class of drugs derived from the Chrysanthemum flower/plant, while pyrethroids are synthetic derivatives. Pyrethrins and pyrethroids typically come in varying concentrations (from < 1% to up to 55% or more). Higher concentrations can be safely used on dogs; however, cats are very sensitive to these chemicals and cannot metabolize these drugs as well as dogs. One of the most common ways we see cats being poisoned by pyrethrins is by inappropriate application of dog flea and tick medications placed on a cat; this should never be done without consultation with a veterinarian. Less commonly, cats may be poisoned by licking or grooming a flea and tick medication off a dog that had a recent topical spot-on application.

In cats, signs of poisoning include profuse drooling, vomiting, tremoring, hyperexcitability, agitation, seizures, weakness, and difficulty breathing. Untreated, it can be fatal. These signs are rarely seen in dogs unless they are exposed to significantly high concentrations. In dogs, signs of paresthesia (a tingling sensation), scratching, drooling, etc. may be seen. Treatment includes prompt removal of the product by bathing with a liquid dish soap like Dawn, Joy, Palmolivem etc. to remove the greasy substance from the skin and haircoat.

If you think your dog or cat is having side-effects or was exposed to pyrethrins/pyrethroids, call your veterinarian or Pet Poison Helpline® immediately for life-saving treatment advice.

Flea and Tick Medication

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Toxicity Level

Mild to Moderate

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Toxicity Level



The content of this page is not veterinary advice. A number of factors (amount of substance ingested, size of the animal, allergies, etc.) determine what is toxic to a particular pet. If you think your pet has eaten something potentially toxic, call Pet Poison Helpline or seek immediate veterinary treatment.