Q. Is the mosquito repellent toxic to cats?


Q. I have found conflicting information about the safety of Thermacell mosquito repellent devices for cats. It sounds like the active ingredient, allethrin, is toxic to felines if ingested or absorbed through the skin, but the device I’m talking about diffuses it into the air outdoors. If I have one of these devices on my deck, it is safe for our cats to be out there also? (They can’t run away when they’re outside on the deck. It’s built off the second story, and they’re too old to jump.)

Tim Watters
Lansing, Michigan

Dear Mr. Watters,

A. Both allethrin and its cousin, permethrin, are toxic to cats for sure. Signs of toxicity include muscle tremors, seizures, hypersalivation, depression, vomiting, loss of appetite, and if the exposure is severe enough, death. That said, your cats should be fine if they share the outdoors with a mosquito repellent that is diffused into the air, comments Tufts emergency and critical care veterinarian Elizabeth Rozanski, DVM. Just don’t let them get too close to the dispenser. If it is on a table, for instance, don’t let them hang out there, as the concentration of the active ingredient will be higher.



  1. Thanks for this. I would like to follow up: I have the same exact situation! My cats stay in my garage at night (we live way out in the country), and I sometimes work in the garage at night… but the mosquito problem is insane. Would it be safe to run the Thermacell mosquito repellent inside a closed garage if I leave the (three) windows open the whole time? If I keep them away from the dispenser (It would be placed on top of a high shelf…impossible to reach.


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