Most mammals, including dogs, tolerate permethrin well because it is quickly detoxified by the liver. However, cats lack glucuronidase, an enzyme that the body uses to detoxify certain compounds. This deficiency is believed to be responsible for cats' sensitivity to concentrated permethrin, as well as to acetaminophen and other substances. Signs of Trouble Cats exposed to concentrated permethrin usually act nervous, twitch, shake and may even develop seizures. Treatment consists of thoroughly removing the permethrin product, giving medication to control tremors or seizures and providing fluid and nutritional support.
Immediate treatment offers the best chance of survival.
Most permethrin spot-on products are readily available and are administered without veterinary advice. The labels of these products do include an explicit warning against use on cats, but the warnings often go unnoticed or unheeded because owners are not aware of the potential for severe consequences if the product is used on cats. Also, few labels warn consumers that cats can become ill or die by interacting with treated dogs. Pet owners should be aware that products with similar brand names may contain different active ingredients. Confusion can also result from similar packaging for different types of spot-on flea control products, only some of which are safe for use on both dogs and cats.