Permethrin is an insecticide used in many flea control products formulated for dogs. It is highly toxic to cats and contact of a cat with a permethrin containing product is an emergency. Cats are most commonly exposed to this chemical when topical products for dogs are applied to cats or when cats rub against dogs treated with these products. Clinical signs of permethrin toxicity in cats include muscle tremors, twitching, seizures, salivation, incoordination, fever and dilated pupils. Between 10% and 40% of known permethrin poisoning cases are fatal, therefore cats with suspected poisoning should be taken immediately to the veterinarian. Brands that contain permethrin and can be found in pet stores and grocery stores include: Hartz, Sergeant’s and Zodiac. It is important to check all products labels for indications that the product is for dogs only or not for cats and to check the ingredients label for permethrin. Most importantly, these products should not be used in any household with cats.