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    Safe Cat Flea Treatments & the Danger of Pyrethrin and Pyrethroid Toxicity

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    Updated: September 14, 2020

    Cat Scratching

    You might not have ever heard the words “pyrethrin,” “pyrethroid,” or “permethrin,” but if you hate fleas, ticks, and mosquitoes and have pets, there’s a good chance you’ve got a pyrethrin or pyrethroid-containing product in your home. And if you have a cat, there are things you absolutely need to know about these insect-killing compounds in order to keep your cat safe. 

    Pyrethrins, and the related but more potent, chemically derived pyrethroids, are widely-used insecticides in flea and tick prevention products used around homes and on cats and dogs. They kill insects by preventing their nervous system from functioning properly.

    Unfortunately, pyrethrins and pyrethroids (especially permethrin) are not species-specific in their toxicity, meaning they can also cause severe and significant problems in pets, especially cats (who lack the liver enzymes necessary to process these compounds as they are absorbed through the skin). 

    Not only is pyrethrin/pyrethroid toxicity a dangerous and distressing situation for your cat, it’s also a major hit to your heart and wallet. Treatment for a pyrethrin toxicity can cost several hundred to a couple thousand dollars. It’s just not worth the risk, especially when there are far safer alternatives available.

    Did You Know?

    Pyrethrin is the natural derivative of the chrysanthemum flower. Pyrethroid refers to the class of synthetic (stronger) derivatives of pyrethrins, such as permethrin.

    It should be noted that pyrethrin/pyrethroid-based flea products are not always dangerous — these compounds can effectively control fleas (and ticks) and, when used correctly and according to label directions, they can be safe for use on both cats and dogs. However, I do believe there are often far safer options you can use to eliminate and control fleas on your cats and in their environment. These safer alternatives are equally as effective, or in many cases more effective, than the pyrethrin/pyrethroid-based products.

    Safe and Effective Flea Treatment Products for Cats

    If you have a cat or multiple cats and would like to avoid pyrethrin/pyrethroid-based products, which I typically* recommend to any cat owner, below are some of the safer and most-effective flea control products for cats. Some of the products recommended below are also effective for tick and/or other parasite control on cats.

    • Advantage® II (spot-on)
    • Advantage MULTI (spot-on, also protects cats from heartworms, ear mites, and some types of intestinal worms)
    • Bravecto® (spot-on, also protects cats from certain tick species)
    • Bravecto® PLUS (spot-on, also protects cats from heartworms, certain tick species, and some types of intestinal worms)
    • Cheristin® (spot-on)
    • Comfortis™ (oral)
    • Revolution® PLUS (spot-on, also protects cats from heartworms, ear mites, certain tick species, and some types of intestinal worms)
    • Seresto® (collar, also protects cats from certain tick species)

      *Note that the Seresto® collar DOES contain flumethrin, a pyrethroid compound. I've included this collar in the flea control products recommended for cats list for a few very good reasons though. First and most important is because the collar has undergone rigorous pre-market testing that demonstrated both its efficacy and safety for use on cats (see Seresto® studies here and here) and, like all such products, it continues to be subject to monitoring. Second is that, like the other active ingredient (imidacloprid), the flumethrin in the Seresto® collar is contained and slowly released from within a unique collar matrix, ensuring that a cat is exposed to both effective and safe levels of the active ingredients throughout the entire 8 month duration of action of each collar. Third is because for some cats and some cat owners collars may be the most cost effective and practical solution for controlling fleas and the Seresto® collar is the best collar option in these situations.

    Do Not Put Dog Flea Control Products on Your CatCat and Dog Sleeping Together

    Pyrethrin/pyrethroid toxicity in cats is most commonly the result of someone who, in an effort to save time or money, used a pyrethrin/pyrethroid-containing product intended for dogs on their cat(s). This is rarely a good idea for any product, but it's especially dangerous when those products contain pyrethrin, permethrin, or another pyrethroid. The amount of pyrethrin/pyrethroid “active ingredients” in the products made for dogs is far too much for cats to handle. 

    In fact, the frequency of cat pyrethrin/pyrethroid toxicity cases resulting from inadvertent (or intentional) application of a dog product to cats was so high that in 2010 the EPA improved product labeling rules for spot-on products for pets to help prevent these inadvertent and intentional species "mix-ups." 

    “New restrictions will be placed on these products, and pet owners need to carefully read and follow all labeling before exposing your pet to a pesticide,” the EPA’s Steve Owens said in a press release announcing the changes.

    Unfortunately, even when you use dog products safely and according to manufacturer’s instructions on your dog, it's still possible for your cat to develop pyrethrin toxicity. This is because cats snuggle with and groom dogs, which can lead to accidental pyrethrin exposure and an unwelcome trip to the veterinary ER.

    The Signs of Pyrethrin and Pyrethroid Toxicity in Cats

    Cats that have been exposed to a large amount of pyrethrin/pyrethroid-based insecticides will often have whole-body tremors. Other signs resulting from pyrethrin/pyrethroid toxicity often include: 

    • Excessive salivation/drooling
    • Agitation or restlessness
    • Vomiting
    • Loss of coordination
    • Difficulty jumping, standing or walking
    • Shaking, twitching, muscle tremors (often mistaken for seizures)
    • Difficulty breathing

    If left untreated, pyrethrin/pyrethroid toxicity can be fatal to cats.

    Treatment for Pyrethrin/Permethrin Toxicity

    Cat Bath

    If the toxicity is due to skin overexposure, initial treatment should include a bath in cool water with a good grease-dissolving dish soap (most veterinarians tend to use Dawn® dish soap). Some cats will require multiple baths. Note that you must be careful not to get water into your cat’s mouth and lungs during the bath, as your tremoring cat will be less able to protect their own airway. 

    If the toxicity is due to ingestion of pyrethrin/pyrethroid, such as from grooming behavior, bathing will do little to nothing to help. In such cases, skip the bath and head straight to the vet. 

    Following any at-home bath(s) for skin exposure, an affected cat should still be brought to the vet for evaluation and further treatment. Remember to bring the flea prevention box with you, as this will help your veterinarian with their diagnosis and treatment plan. Additional treatment could include: 

    • Additional baths
    • Injectable medications to stop muscle tremors
    • IV fluid therapy to restore and help maintain hydration while the cat can’t eat safely on their own
    • IV lipid therapy to help absorb and clear the toxin
    • Temperature support

    Even with appropriate treatment, some affected cats can be left with long-term neurologic issues. Spare your cat, and yourself, the trauma by taking the proper steps to avoid exposure in the first place. 

    How to Protect Your Cat from Pyrethrin Toxicity

    To prevent pyrethrin/pyrethroid toxicity in your cat, while still keeping them free of fleas and other parasites, take the following preventive measures: 

    • Read Up: Regardless of what product you use to kill and control fleas or other parasites, always follow label instructions and warnings.

    • Check All Sources: Remember that it isn’t just the products you use on your cat. Your dog’s flea control product might contain pyrethrin or a pyrethroid that your cat can ingest through grooming. Additionally, some outdoor plant insecticides contain pyrethrins/pyrethroids, which can lead to toxicity if your cat goes outside and eats plants covered in those insecticides.

    • Research: Learn more about flea treatment and prevention, and be sure to discuss this important topic with your veterinarian. Flea prevention and control is about far more than just a monthly dose of medication in the summer months. The best flea prevention and control is typically throughout all 12 months of the year!

    • Be Consistent: It’s of the utmost importance that you treat all of your pets and their environment throughout the year. Flea control isn’t just about maintaining your pets’ comfort (although that’s definitely important); fleas also spread some pretty nasty diseases to both pets and people. 

    Flea allergy landing

    Products that Contain Pyrethrin

    If you’re worried about pyrethrin toxicity, and have opted to use a flea treatment for your cat not listed in the alternatives provided above, make sure you carefully read the labels.

    Check for the pyrethroid class of compounds and be sure that such compounds are either not in the flea medications or mosquito/insect repellents used around your cats (there are no safe mosquito repellents for cats, but you should nevertheless learn how to keep your cat safe from heartworms) or that the compounds are in a collective concentration —meaning you’ll need to consider the total of all pyrethroid compounds — that falls below the typically safe level of 1%.

    The following list of pyrethroid compounds was pulled from a fairly comprehensive article on Wikipedia (you can also find more information about pyrethrins and pyrethroids from the EPA). As you can see, the list of compounds can be difficult to keep track of, and I highly recommend sticking to a pyrethrin-free product, such as the safe cat flea treatments listed above.

    Important note: Many consumer pest control products that you might use in your garden or yard contain pyrethrin or pyrethroids. Do not let your cat come into contact with with these outdoor insecticides — either through contact with treated plants or airpborn spray— and if neighborhood outdoor cats venture into your yard without your control, consider using a non-pyrethrin/pyrethroid product. This could also be a concern if you hire a pest control service, which may use a pyrethrin/pyrethroid-based insecticide in and around your home. Be sure to ask and specify that you need pet-safer methods and products to be used.


    • Allethrin, the first pyrethroid synthesized
    • Bifenthrin, active ingredient of Talstar, Capture, Ortho Home Defense Max, and Bifenthrine
    • Cyfluthrin, an active ingredient in Baygon, dichlorovinyl derivative of pyrethrin
    • Cypermethrin, including the resolved isomer alpha-cypermethrin, dichlorovinyl derivative of pyrethrin
    • Cyphenothrin, active ingredient of K2000 Insect spray sold in Israel and the Palestinian territories
    • Deltamethrin, dibromovinyl derivative of pyrethrin
    • Esfenvalerate
    • Etofenprox
    • Fenpropathrin
    • Fenvalerate
    • Flucythrinate
    • Flumethrin (Note the exception regarding flumethrin in the note about the Seresto® collar above)
    • Imiprothrin
    • lambda-Cyhalothrin
    • Metofluthrin
    • Permethrin, dichlorovinyl derivative of pyrethrin and most widely used pyrethroid.
    • Prallethrin,[9] active ingredient in Baygon and All Out (India)
    • Resmethrin, active ingredient of Scourge
    • Silafluofen
    • Sumithrin, active ingredient of Anvil
    • tau-Fluvalinate
    • Tefluthrin
    • Tetramethrin
    • Tralomethrin
    • Transfluthrin, an active ingredient in Baygon

    Topics: flea control, flea treatment, pyrethrin

    Please do not ask emergency or other specific medical questions about your pets in the blog comments. As an online informational resource, Preventive Vet is unable to and does not provide specific medical advice or counseling. A thorough physical exam, patient history, and an established veterinary-patient-client relationship is required to provide specific medical advice. If you are worried that your pet is having an emergency or if you have specific medical questions related to your pet’s current or chronic medical conditions, please contact or visit your veterinarian, an animal-specific poison control hotline, or your local emergency veterinary care center.

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