Is It Safe to Use Dog Flea and Tick Products on Cats?

Published May 25, 2022

Fleas and ticks are parasites that can transmit diseases, cause discomfort, and establish a presence in your home and yard. Since pets come in various sizes, it may seem okay to use a dog flea and tick product on your cat. But there are many factors, not only weight, that need to be considered before choosing the right flea and tick medication for your cat. In fact, it is dangerous and sometimes lethal to use a canine-specific flea and tick medicine on a cat.

Dogs and cats have very different liver metabolisms, and many medications that can be safely used in dogs are toxic to cats. Warnings are typically placed on medication labels, but you must read directions carefully and only use products for your cat that are specifically made for feline use.

Why Are Dog Flea and Tick Products Dangerous for Cats?

The danger to cats from dog flea and tick products is linked to pyrethrins, a blending of six chemicals that is toxic to ingest (it is also a naturally occurring substance in some chrysanthemum flowers). Pyrethrins have a synthetic derivative known as pyrethroids. One type of pyrethroid, permethrin, is a common ingredient in dog flea and tick products and is lethal to cats. Permethrin can be inhaled, ingested, or absorbed through the skin.

These chemicals are commonly found in household insect sprays, as well as flea and tick preventives and treatments for dogs. Permethrin can be found in many formulations including:

  • Insecticides

  • Dog flea and tick medications, including topical products and collars

  • Environmental flea and tick treatments and preventives, including liquids, powders, dusts, aerosols, and sprays

  • Some repellent-treated clothing (typically includes hiking, gardening, outdoor gear)

There are currently over 1,400 registered U.S. products containing permethrin.

Pyrethrins, pyrethroids, and permethrin can be found in many common formulations that you likely have  around your home. These chemicals are dangerous to cats, and it is important to proactively prevent exposure. They can cause serious side effects, even death.

What Happens When a Cat Ingests Permethrin?

Signs of pyrethrin (including permethrin) toxicity in cats can include:

  • Excessive salivation/drooling

  • Vomiting

  • Hiding

  • Restlessness/anxious behaviors

  • Lack of coordination

  • Tremors/muscle twitching

  • Seizures

  • Abnormal breathing

  • Excessively low or high body temperature

Cats can ingest pyrethrin from oral, respiratory, and topical routes, including licking or grooming a companion dog that has been treated, walking through moist areas recently treated, or rubbing against surfaces where permethrins have recently been applied.

If your cat gets into a flea and tick product that is made for dogs, seek veterinary care as soon as possible to limit complications.

Your veterinarian may be able to treat your cat on an outpatient basis, or hospitalization may be required. The prognosis depends on the severity of the exposure, the clinical signs your cat is displaying, and the response to treatment. The prognosis can range from good to poor; cats can die from pyrethrin toxicity.

If in doubt, contact the Animal Poison Control Center or the manufacturer of the flea/tick medication to discuss details about exposure.

Why Can’t Cats Use Dog Flea and Tick Medications?

There are two main reasons why cats cannot process flea and tick medication manufactured for dogs. Similarly, you should not use feline flea and tick medications on dogs.

Cats Respond Differently to Medication

Cats and dogs have differences in their liver metabolism. This is the key reason permethrins can be used safely in dog flea and tick products, but are not used in cat flea and tick products. Since a cat’s system cannot metabolize the chemical safely, there can be negative and even lethal side effects on many organ systems, including respiratory, nervous, and gastrointestinal.

Size Matters

Your cat’s size is an important factor when determining the right dose for flea and tick medication. Medicine is not always distributed evenly throughout a pill or liquid. It is best to use the appropriate size for each pet. It’s important not to give a partial tablet or liquid spot-on from a weight range larger than your cat. It is also best to avoid buying two packets of a smaller weight-size medication and using them together. Weigh your cat and use the appropriate treatment or preventive for their weight range. Your veterinarian can help you get an accurate weight before determining an appropriate dosage.

The weight of the pet (cat or dog) is not the only factor in determining medicine dosage and absorption. When using flea and tick products for your cat, use only a product labeled for cats. Dogs and cats process drugs differently and formulations made for cats are based on unique needs such size of pill, flavoring, and concentration of medication. There are ingredients in dog flea and tick products that are toxic to cats, including pyrethrins and pyrethroids.

Flea and Tick Medications Safe for Cats and Dogs

There are several brands and formulations of medication that have safe flea and tick preventives and/or treatments for both cats and dogs. Below is a list of medications labeled specifically for cats that are safe when used at the appropriate dose.

There are some differences between products labeled as prevention or treatment. Many forms of use are available to choose from, based on what best fits you and your cat’s lifestyle and environment. The following can be helpful in the management of flea and tick parasites:

  • Flea and tick preventative collars

  • Oral pills or chewables

  • Topicals like shampoos, sprays, and wipes specific to treating fleas and ticks

  • Home and yard treatments including pesticide treatments that are safe for pets

  • Combs and brushes to help look for fleas and ticks on your cat

It’s important to find a flea and tick preventative that works for your cat, and to ensure their safety whenever introducing a new medication into their life. Always discuss a change in medication or any questions around flea and tick prevention with your veterinarian to determine the best option.


  1. Toynton, K.; Luukinen, B.; Buhl, K.; Stone, D. National Pesticide Information Center. Permethirn Technical Fact SheetMarch 2009.

  2. Gwaltney-Brant, S. Veterinary Information Network. Pyrethrin/Pyrethroid Toxicosis (Feline). January 2016.

Featured Image: Milena Valero Orjuela


Amanda Simonson, DVM


Amanda Simonson, DVM


I am a veterinarian passionate about helping animals. I practiced for 15 years in the hospital setting doing medicine, surgery, preventive...

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