When I was a little girl, my family had a cat named Suki. I loved the animal shelter more than I did visiting the zoo, and I picked Suki out myself.
Back in the 80s, we didn’t have spot-on flea treatments or any of the other advances in flea control we do today. What we had were flea collars and flea dips you had to bathe your dog or cat in. We also had whole-house foggers that would spew chemicals into the furthest corners of your home, hoping to kill off all of the fleas.
Living in north Florida, we didn’t have the kind of harsh winter that killed off all the fleas like you get in some parts of the country, so fleas were a real problem. When Suki and our dog at the time had a persistent flea infestation, they were both subjected to frequently repeated flea dips to try to get it under control.
One Sunday morning when I was eleven years old, Suki threw up her breakfast. That’s not so unusual for a cat. But what was unusual was that a while later she started convulsing and wouldn’t stop. It went on and on, and it was terrible.
My mother sent my sister and me off to Sunday school with a carpool ride, and she went to the vet. I couldn’t concentrate on anything anyone was saying that morning. I just wanted to know how my beloved cat was. Suki never came home, and I never saw her again even to say goodbye.
Fast forward 30 years or so, and I read a description of permethrin poisoning in cats from flea products. It brought the awful scene from that Sunday morning flooding back. I had the sinking realization permethrin, found in flea dips, had killed Suki.
Many flea solutions contain the pyrethrins, an insecticide with an active ingredient permethrin. This is a synthetic form of a naturally occurring extract from the Tanacetum cinerariifolium flower, part of the chrysanthemum family.
But instead of being a flower, permethrin is a neurotoxicant. It kills fleas by over-exciting their nerves.
Unfortunately, cats are especially sensitive to permeterhins because they can’t metabolize them quickly enough. As a result, permethrin is the most common cause of poisoning of cats in the US. They can cause neurological symptoms like tremors, seizures, and hypersalivation. In some cases, they can even cause death.
Permethrin has been eliminated from most products labeled for cats, though you may still find it today as an ingredient in flea dips labeled for use for both cats and dogs. Products are allowed to be labeled for use in cats when they contain low levels of permethrin. To be safe, always use a product specifically labeled as safe for cats, and avoid pyrethrin and permethrin ingredients.
Cats can be exposed to permethrin by being given a flea product labeled for dogs, or by spending time in close contact with a dog who has had a topical flea product applied. They can also be exposed to it when it is used in insectisides for the garden.
There is no antidote for permethrin/pyrethrin poisoning in cats. Treatment is limited to removing as much of the toxin from the skin as possible to prevent absorbing more and to supportive care.
Questionable Internet Flea Treatment Advice
Today, with the convenience of the internet, it’s easy to reach out to others who love the same things we do for advice and support. As a result, I am often among groups of animal lovers online. Far too often, I see people giving the advice that you can save money on cat flea control by buying a big dog flea medication then splitting the dose up among many cats.
When I see this, I try to warn that it is dangerous, pointing out permethrin poisoning is a risk if you don’t know what is in the dog flea treatment. Answers have ranged from “I’m in rescue and I know what I’m doing” to “I have done it plenty of times and nothing bad has ever happened.” I don’t want to argue with people on the internet, but I don’t want to stand by and watch cats be killed like my Suki, either.
Recently, I have started leaving Facebook groups when this issue comes up because I don’t have the heart to have the same argument over and over again. Even if the person who asked the question reads my warning, the next person who skims past trying to find a quick answer won’t, and I can’t stand to see the tragic results show up in the group later.
A Safer Flea Treatment Plan
If you need to use a flea product for your cat, consider a bath with a few drops of Dawn dish soap, which is often used on kittens too young for flea chemicals. If you use a chemical flea treatment, make sure it’s a flea product labeled for cats and doesn’t contain permethrin. If you are at all unsure about the product, ask your veterinarian about their experience with it.
Also, make sure you know how much your cat weighs. Flea treatment is generally applied by weight, and you can overdose a cat if you guess their weight wrong. Your vet will be happy to set up a weigh-in for your cat if you don’t have an appropriate scale, possibly even at no charge.
Keep your cat safe and happy this flea season!
Research and further reading
Journal of the American Veterinary Medical Association, Toxicosis in cats erroneously treated with 45 to 65% permethrin products.
Journal of Feline Medical Surgery, Feline permethrin toxicity: retrospective study of 42 cases.