Flea and Tick Medicine Poisoning in Cats

Veronica Higgs, DVM
By Veronica Higgs, DVM on May 26, 2022
A big white cat laying down and licking herself.

In This Article


What Is Flea and Tick Medicine Poisoning in Cats?

Some pet flea and tick medications—including topical sprays, dips, and shampoos—contain pyrethrin and/or pyrethroid. Pyrethrin and pyrethroid may also be found in insecticidal agricultural and home products.

Pyrethrin is an insecticide derived from Chrysanthemum cinerariaefolium (“mum”) flowers. Pyrethrins are safe to use in cats if administered at appropriate doses. Pyrethroid is the synthetic version of pyrethrin, designed for enhanced stability and potency. Pyrethroids are not safe to use in cats. The most common pyrethroid is called permethrin, which is found in over-the-counter spot-on products labeled for dogs and is metabolized (broken down) in the liver. 

Your cat’s liver is very inefficient at processing permethrin, which causes it to build up, leading to poisoning or toxicity.

If your cat’s symptoms are not treated, this toxicity may lead to seizures and death within a few hours. Permethrin toxicity may also occur in dogs, but it is rare and typically only at very high doses.   

Symptoms of Flea and Tick Medicine Poisoning in Cats

Poisoning symptoms in cats usually occur minutes to hours after exposure to or application of the flea and tick medicine, but may be delayed up to 72 hours. The symptoms typically last two to three days.  

The most common symptoms of flea and tick medicine poisoning in cats include:  

  • Tremors/muscle twitching/trembling 

  • Ear twitching  

  • Loss of balance or stumbling (ataxia)  

  • Lethargy  

  • Drooling (hypersalivation)  

  • Itchiness  

  • Hiding  

  • Agitation  

  • Vomiting/diarrhea 

  • Seizures and death if symptoms are untreated 

Causes of Flea and Tick Medicine Poisoning in Cats

Causes of flea and tick medicine poisoning in cats include:

  • Accidentally or intentionally applying dog flea and tick medicine to a cat
  • A cat brushing against, laying with, or licking a dog that recently had spot-on medicine applied. Such medicines can take up to 24 hours to dry.  
  • Sensitivity to appropriately applied/dosed flea and tick products 
  • Overdose  

You should never apply dog flea and tick products to cats. Cats are not small dogs!  

You should always use the correct weight range on the product’s packaging to determine the appropriate dose.

How Veterinarians Diagnose Flea and Tick Medicine Poisoning in Cats

Your veterinarian will ask for a detailed history of any topical medication, shampoo, dip, or spot-on medicine applied to your cat or other pets in your household. If possible, take the product and packaging for the vet to examine. 

Your vet will start with a thorough physical examination to assess your cat’s neurological status. A complete blood count, serum blood chemistry, and urinalysis will likely be recommended for a baseline evaluation.   

Unfortunately, there is no specific toxicology test available to determine if your cat was exposed to pyrethrin or pyrethroid. Therefore, the history of exposure to these products is valuable information for your vet. 

Early detection and treatment are key to your cat’s successful recovery.   

Treatment of Flea and Tick Medicine Poisoning in Cats

If your cat is experiencing poisoning symptoms, they should be treated as quickly as possible.

If you realize you accidentally applied a dog product to your cat, or your cat starts to show symptoms after recent application of a spot-on product to them or to other pets in the household, call your vet immediately for assistance.

Depending on the severity of your cat’s symptoms, to prevent further absorption of the product, your vet may instruct you to immediately bathe your cat in diluted dishwashing liquid (such as Dawn) and go to a local emergency veterinary hospital.

The emergency vet will assess your cat’s temperature and neurological status. It is likely your cat will be hospitalized for up to three days while undergoing treatment.

There is no known antidote for permethrin toxicity in cats, so treatment mainly consists of supportive care to treat the neurological signs listed above. This may involve:

  • IV muscle relaxers

  • IV fluids

  • Anti-nausea medication  

Your vet may also recommend a newer treatment called intralipid therapy, which helps pull the permethrin out of cat tissues faster and lessens symptoms.    

Recovery and Management of Flea and Tick Medicine Poisoning in Cats

Your cat’s symptoms may last for up to three days, even if you try decontaminating them in diluted dishwashing liquid. Hospitalization is recommended until your cat’s tremors or twitching resolve and they are back to normal.  

Prognosis is excellent for early and aggressive treatment. However, if your cat’s severe neurological symptoms are untreated or are treated very late, permethrin toxicity in cats can be fatal within a few hours.

Typically, cats that recover go on to live normal lives with no secondary consequences.   

Prevention of Flea and Tick Medicine Poisoning in Cats 

Prevention of flea and tick medicine poisoning in cats (permethrin toxicity) is key when it comes to avoiding an emergency with your cat. It’s critical to remember:

  • Never put a dog flea and tick medication product on a cat

  • Always follow the product recommendations for dosing

  • Ask your vet about flea and tick prevention product recommendations for your specific pet   

  • Separate your cat for 24 hours from any dogs that were treated with a topical product

  • If you have a cat and a dog in one household, ask your vet for a dog flea and tick medicine that does not contain permethrin  

  • Keep all flea and tick medication in a safe place away from animals   

Flea and Tick Medicine Poisoning in Cats FAQs

What happens if your cat licks flea medicine?

Licking a permethrin-based spot-on flea and tick product for dogs is toxic to cats. If your cat has brushed up against or licked a dog within 24 hours of a spot-on flea and tick medication application, call your vet immediately. If your cat licks a cat-safe flea and tick medication, the bitter taste will typically cause drooling and possibly nausea.   

How long does your cat’s flea medicine toxicity last?

Toxicity from your cat’s exposure to permethrin-based spot-on flea and tick products for dogs may last up to three days. Never put a product labeled for a dog on a cat. Cats are not small dogs!  

How do you stop your cat from licking flea medicine?

Spot-on flea and tick products may take up to 24 hours to dry. It is very important to separate dogs from cats in the household for 24 hours after applying permethrin-based spot-on medicine to dogs.

If you apply a cat-safe flea and tick spot-on product to your cat, be sure to do it at the nape of the neck. This should keep the cat from reaching and licking the product.

Featured Image: iStock.com/sdominick

Veronica Higgs, DVM


Veronica Higgs, DVM


Dr. Veronica Higgs is a 2010 graduate from Auburn University College of Veterinary Medicine.  She then completed a 1-year rotating...

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