Pet Care Resources What You Should Know About Flea Product Toxicity in Dogs and Cats

Emergency Medicine, Dermatology

What You Should Know About Flea Product Toxicity in Dogs and Cats

Fleas are a common pest for both cats and dogs. They are a parasite that feeds on your pet’s blood. Their bites can cause your cat or dog to itch. More importantly, fleas can be a vector for infectious diseases (cat scratch fever) that affect humans.

We’re fortunate to have safe, effective products for our dogs and cats to protect them from fleas, ticks, and other ectoparasites. Flea and tick preventative is recommended for most dogs and cats and is best if used year-round. When used as directed, such products are safe and effective. However, dogs and cats can easily become sick if too much or the wrong flea product is applied or given or if a product for dogs is used in or on cats. Below is more information about potential reactions and flea control product toxicity in pets.

Prevention of Flea Control Product Toxicity in Dogs and Cats

Before applying or administering a flea control product to your pet for the first time, consult your family veterinarian. They’ll give you the best recommendations for your pet and help you navigate the available options. 

Flea Product Dos and Don’ts

Dos for flea control products: 

  • Use a veterinarian-prescribed or recommended flea control product.  
  • Read label directions carefully and follow them. 
  • If a topical product is applied, separate pets in a multi-pet household until the flea control product is dry so pets cannot lick topical products off each other. 
  • Store flea control products in a secure location away from children and pets. 

Don’ts for flea control products:  

  • Don’t use flea control products on or in young puppies, kittens, or on a pregnant or nursing pet without consulting your veterinarian and reading the label. Most products have a minimum age for use on the label.   
  • Don’t apply a topical flea control product to skin that’s red, irritated, scratched, or broken. 
  • Don’t use more than one flea control product on your pet at a time unless prescribed by your veterinarian.  
  • Don’t apply a flea control product for a dog to a cat.  

Toxicities and adverse reactions to a product will be on the label. If you have questions, discuss it with your veterinarian or their knowledgeable care teams.  

Signs of Flea Control Product Toxicity in Cats and Dogs

Toxicity is rare and usually occurs when a product for dogs is applied to a cat. Signs of flea control product toxicity can occur from one to 12 hours after application and may vary depending on the type of flea control product poisoning. Cats are more sensitive to the toxic effects of pyrethrums and organophosphates than dogs, so take care when using flea control products of any type on a cat.  

The most common signs of toxicity from pyrethrum-based flea products are muscle tremors and excessive salivation. Common signs of toxicity from flea control products containing organophosphates are diarrhea, vomiting, difficulty breathing, small pupils, muscle tremor, weakness or falling over, and drooling.

Organophosphate toxicity can be rapidly fatal, depending on the ingredients and dose the pet is exposed to. 

What to Do if Your Dog or Cat has Flea Control Product Toxicity

If you suspect your pet is experiencing flea product toxicity, it is recommended that you immediately wash your pet with warm water and a mild dishwashing liquid, such as Dawn® and contact your family veterinarian immediately or bring your pet to the closest MedVet veterinary emergency clinic.

Common Flea Control Products

Be sure to read labels for flea and tick control products and speak with your veterinarian for which products are best for your pet as there are many options available for dogs and cats.

Common effective products include:  

  • The Isoxalaners (Nexgard, Bravecto, Simparica) 
  • There is still a place for Fipronil (Frontline Plus and its variations), and this is over the counter.  
  • There is still a place for Imidacloprid (Advantage and its variations). K9 Advantix and its variations should only be applied to dogs.  
  • Selamectin is another effective molecule for flea prevention, and Revolution is an FDA-approved treatment for sarcoptic mange in dogs. Revolution Plus is for cats. 
  • Seresto collars may be recommended for food allergic dogs or cats or in patients with epilepsy, or when a topical or oral flea prevention product cannot be used. 
  • Lufenuron, still in Sentinel for dogs, is a growth regulator and very beneficial in a flea control program. 

Ingredients used in older flea control products

Many previously used products were pyrethrum-based, and the label may list the main ingredient as pyrethrum, pyrethroid, or permethrin.  

Pyrethrum-based flea products include: allethrin, bifenthrin, cyfluthrin, cypermethrin, cyphenothrin, deltamethrin, esfenvalerate, etofenprox, fenpropathrin, fenvalerate, flumethrin, imiprothrin, metofluthrin, permethrin, prallethrin, resmethrin, silafluofen, sumithrin, tefluthrin, tetramethrin, tralomethrin, and transfluthrin as well as others.  

The other type of flea product that can cause toxicity contains organophosphates. Active ingredients in organophosphate products include: chlorpyrifos, crufomate, dichlorvos, diazinon, haloxon, naphthalophos, phosmet, naled, tetrachlorvinphos, and malathion.

By Lauren Pinchbeck, DVM, MS, Diplomate, ACVD |
August 7, 2023