Is dog flea treatment (permethrin) toxic to cats?
Yes, severely. Permethrin, common in dog flea spot-ons, sprays and collars, causes tremors and seizures in cats and is often fatal without treatment. Even a small amount of a dog product, or close contact with a freshly treated dog, can be enough. Go to a vet now. If the product is on the fur, wash it off with lukewarm water and mild soap on the way, if your cat allows it.
General information, not veterinary advice. If your pet may have eaten this, contact a vet now; do not wait for signs.
What to do right now
- Call your vet and head there now
- If you can do it quickly, wash the area with lukewarm water and mild soap or washing-up liquid, then rinse well
- Dry your cat with a towel and keep it warm so it does not get chilled
- Take the product packaging with you
- Keep the treated dog away from your cat
Go to an emergency clinic now if
- A dog flea or tick product was put on your cat
- Your cat groomed or slept against a dog treated in the last few days
- Twitching, trembling or shaking
- Unsteady walking, wide pupils or heavy drooling
- A seizure or trouble breathing
Who to call
Your own vet first. If they are closed, the nearest emergency or out-of-hours clinic.
In the United States
Both answer 24 hours a day and may charge a consultation fee.
Signs to watch for
| Sign | Usually starts |
|---|---|
| Drooling | Minutes to a few hours |
| Twitching | A few hours (up to 36 hours) |
| Tremors and shaking | A few hours (up to 36 hours) |
| Wobbling, wide pupils, sensitivity to touch and sound | A few hours |
| Seizures | Hours, severe cases |
| Difficulty breathing or blindness | Less common, severe cases |
Why is permethrin toxic to cats when it is safe for dogs?
Permethrin is a synthetic insecticide, a pyrethroid, used in many flea and tick products for dogs. A cat's liver cannot break it down into a harmless form, so it builds up in the body and overstimulates the nerves. The Merck Veterinary Manual notes that among pets, cats are the most sensitive to pyrethroids.
Dog spot-ons often contain permethrin at high strength, made for an animal several times a cat's weight. That is why International Cat Care stresses that a dog product cannot be made safe for a cat by using less of it.
How do cats come into contact with permethrin?
Most cases happen when a dog spot-on is put on a cat by mistake, often because cat and dog packs look alike. A cat can also be poisoned by rubbing against, grooming or sleeping next to a dog treated in the last few days. Household flea sprays and powders can contain permethrin too. Low-strength products made for cats are a different matter, so always check the label and the species.
Why wash it off, and how?
Washing removes product that has not yet been absorbed and stops your cat swallowing more while grooming. Use lukewarm water and a mild soap or washing-up liquid, rinse thoroughly and dry your cat well so it does not get cold. Do not use flea shampoo, which may contain more insecticide. If your cat fights you, stop and go: the vet will wash it under safer conditions.
What will the vet do?
There is no antidote for permethrin. The vet will wash off remaining product, give medicine to stop tremors and seizures, put your cat on a drip of fluids, and monitor its temperature. Some vets also use an intravenous fat emulsion that may help draw permethrin out of the tissues. Cats treated early usually make a full recovery, while cats with seizures that are hard to control have a poorer outlook.
How do I stop it happening again?
Buy flea treatment for your cat only from products labelled for cats, and be careful with online listings that do not show the active ingredient. In a home with both dogs and cats, choose a dog flea treatment without permethrin. If you do use one, keep the dog and cat apart for 72 hours. Store dog and cat products separately so they cannot be mixed up, and if you are not sure whether a product contains permethrin, read the active ingredients or ask your vet before using it anywhere near your cat. Tell sitters and anyone else who treats your pets, since the mistake is easy to make when packs look the same. Pativo's toxin lookup recognises "dog flea" products and permethrin, and it works offline on your phone.
Questions owners ask
Can I use a smaller amount of my dog's flea treatment on my cat?
No. A smaller amount of a dog product can still poison a cat. Use only products labelled for cats, ideally ones your vet recommends.
I treated my dog with permethrin. How long should I keep my cat away?
International Cat Care advises keeping a permethrin-treated dog and cat apart for 72 hours. Better still, choose a dog product without permethrin.
Should I wash my cat before going to the vet?
Only if it is quick and your cat tolerates it. Getting to the vet matters more, so do not let washing delay you, and keep your cat warm afterwards.
Sources
- International Cat Care: Permethrin Poisoning
- PDSA: Permethrin Toxicity in Cats
- Merck Veterinary Manual: Plant-Derived Insecticide Toxicosis in Animals
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