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

Author: Dr. Stephanie Austin

Published: December 14, 2021

Updated: July 6, 2022

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long haired grey cat laying down while someone applies topical flea preventativeThey may have four legs and fur, and some may even play fetch or walk on a leash.

But the harsh truth is, no matter how much they may look or act like one, your fuzzy feline is just not a dog.

And this is also true for your cat's flea prevention products and the danger if you accidentally or intentionally apply DOG flea or tick preventative to your cat.

The ingredients in dog flea and tick products are highly toxic and even fatal if used on cats. The long and the short of it is: DO NOT APPLY DOG FLEA & TICK PREVENTATIVES TO CATS.

Why Dog Flea & Tick Preventatives Should Never Be Used on Cats

It has to be repeated to be remembered — cats are NOT small dogs. This may seem obvious. However, their metabolisms and internal systems work very differently. When you use flea and tick medications not intended for cats on a cat, the effects can be disastrous.

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 our pets. They kill insects by preventing their nervous system from functioning properly. However, these products are not species-specific and can cause severe and significant neurologic problems when applied to certain pets — specifically cats.

Cats lack the liver enzymes necessary to process these compounds safely. The result can be fatal in some cases. Read more about pyrethrin toxicity in cats.

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, below are some safer, effective flea control products for cats.

We didn’t include any over-the-counter (OTC) medications for good reason, as many are not as effective or safe in every circumstance. For more information on the benefits of prescription preventatives over OTC ones, you can check out our article on over-the-counter vs. prescription flea and tick preventatives for more information.

  • Advantage® II (topical liquid)
  • Advantage MULTI® (topical liquid, also protects cats from heartworms, ear mites, and some types of intestinal worms)
  • Bravecto® (topical liquid, also protects cats from certain tick species)
  • Bravecto® PLUS (topical liquid, also protects cats from heartworms, certain tick species, and some types of intestinal worms)
  • Cheristin® (topical liquid)
  • Comfortis™ (chewable tablet)
  • Revolution® PLUS (topical liquid, 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)

Your Veterinarian Will Help You Choose the Best Flea Treatment for Your Cat

There are several factors your veterinary team will take into account when helping you select the best flea/tick preventative for you and your cat. In addition to the basics such as their age, breed, and weight, these include:

Location: What region you’re located in and the impact these environments/temperatures have on fleas and ticks, and other parasites.

Lifestyle: Your cat’s lifestyle – are they indoor-only, or are they allowed outside? If so, is this outdoor space controlled (i.e., a backyard, or are they on a leash?), or do they roam freely?

Your family: Do you have children or other pets, their ages, and do they interact with your cat?

Travel: Do you travel with your cat? Domestic or international travel? If so, how often and where to?

Treating Fleas at Home

Although it is still possible for fleas to try and take over your home (and your cat!) if you have your cat on an effective flea preventative such as one prescribed by your veterinarian year-round, the chance of this occurring is much less likely.

Additionally, your veterinarian may use these preventatives in combination with other products to treat fleas should you miss a dose and an unfortunate flea infestation occurs. Furthermore, it is important if you have additional pets in your home to make sure they are all on safe and effective flea preventatives as well.

Speaking about other pets, if your cat has fleas, likely, your other pets do too, so they will all need to be treated.

To get rid of fleas at home, you’ll need to:

  1. Use the preventative product your veterinarian gave you as directed
  2. Use a flea comb to remove live fleas and their eggs
  3. Bathe your cat with a flea shampoo ­– one WITHOUT pyrethrin such as Vet's Best Flea Shampoo
  4. Wash everything fabric in HOT water (including cushion covers, bedding, etc.)
  5. Vacuum everything that can’t be washed by hand or in a machine

Why Flea and Tick Preventatives Should Be Used All Year Long

The older school of thought was that fleas and ticks weren’t as active in the winter months. Therefore, it wasn’t necessary to use preventatives during these periods, with saving money as the only real benefit.

However, with more recent climate changes, we have seen warmer winters, cooler summers, and a surge in bugs during these months when we normally wouldn’t see any. Because we can’t predict these parasites’ behavior, it is not recommended you skip any preventative doses anymore, even when it may be cold outside.

Why Skipping a Dose Isn’t a Good Idea

Just like when we are prescribed a medication, we are advised not to skip any doses. The same goes for our pets, including their preventatives. It should be noted that a product will only be effective for as long as the manufacturer states, which is typically one month for most preventative products (depending on the product). Therefore strict compliance is necessary if you wish to maintain a parasite-free home and cat.

Once a preventative has lapsed, it can take on average 24–48 hours for the next dose to start working and to re-start any protection for your cat. The period between protection lapsing can be critical, and it only takes this window for a flea to sneak in and start an infestation.

And this is only one of the reasons veterinarians and veterinary staff promote the use of flea prevention products before fleas can become an issue. Not only are flea infestations difficult, time-consuming, and frustrating, fleas can cause trauma to your cat’s skin, as well as cause allergic reactions in some cats (known as flea allergy dermatitis). They can also carry several nasty intestinal parasites such as tapeworms and, although the risk is low, these parasites can even be transmitted to you!

Why Indoor-Only Cats Need Parasite Preventatives

We can’t forget our indoor-only feline friends. Although many may live in high-rise apartments, and it may seem that they are much less likely to come into contact with fleas or other parasites, you’d be surprised! Indoor plants can attract all kinds of bugs (including fleas), or if you have a dog, then you 100% have a flea magnet in your home.

However, just by you’re going outside into the world, this is enough for you to bring back 1 flea (and that’s ALL that it takes!) to start a flea party in your 6-floor NYC walk-up and reason enough to have your indoor kitty on flea preventatives.

Simply put, preventing fleas and other parasites is far better than trying to eliminate them once they’ve made their way onto your cat and into your life.

Myth-Busting on Cat Flea Prevention

Although fleas and other parasites can be frustrating, to say the least, especially when it comes to finding the right treatment or prevention protocol for your cat and household, often people may consider integrating a combination of treatments. Be it a veterinarian-recommended treatment, such as one of the ones listed above, in addition to an environmental treatment. We did some research and came across some of the slightly less common and perhaps more peculiar treatments out there on the world wide web that we thought were worth mentioning and busting before you give them a try!
  • Black walnut: Administered orally several times a week (for life!) in capsules or liquid form as a preventative. However, black walnut is TOXIC at high doses. Therefore, this is NOT recommended. It also sounds very intense, having to medicate a cat several times a week.

  • Diatomaceous earth: A powder composed of the fossilized remains of single-celled algae that is sprinkled on carpets to get rid of a flea infestation, then vacuumed up. Known to be harmless if ingested; however, please tell your cat not to inhale it as it can be toxic if inhaled. Therefore, all pets should be removed from the home if you choose to use this powder, and you should also wear a protective mask. I don’t believe they make cat masks just yet. And this option alone won’t get rid of the fleas on your cat.

  • Homemade sprays: They may smell great, but their efficacy has not been proven and cannot easily be tested scientifically across many cats, as everyone chooses to beat to their own drum when it comes to creating tinctures. A typical recipe is: five drops each of tea tree oil, citronella oil, rosemary oil, peppermint oil, and eucalyptus oil to one cup of water, shake it, and put it in a spray bottle. However, there are many other recipes out there. Essential oils need to be used in a very dilute form, if at all, around cats. They are very sensitive to them, and some can be toxic, like the tea tree, citronella, and (some types of) peppermint oils in the above recipe! Additionally, these are designed to be used in your cat’s environment and NOT to be sprayed directly on your cat as they can be toxic and harmful if ingested or inadvertently sprayed in their eyes or mouth. Eugenol oil (also known as clove oil), found in some commercially produced flea/tick products can also be toxic to cats unless used as directed.

  • A good ol’ bowl of water & dish soap: This home flea remedy involves creating a flea trap using dish soap and some water. By filling a plate or bowl with a mixture of warm water and dish soap, you then place this potion in the areas of your home that have the most flea activity. This solution acts as a glue, trapping the fleas due to the high viscosity of the solution. You should replace the water/soap trap daily, and it works best at night-time as fleas are nocturnal. Some suggest using a candle near the solution enhances this remedy. However, this is not advised due to the potential fire hazard. It should be noted that this does NOT prevent fleas from biting or infesting your pets and may put your pets at risk for drinking water containing dish soap.

Let us know, in the comments below, how you protect your cat from these horrible little pests.


About the author

Profile picture for Dr. Stephanie Austin

Dr. Stephanie Austin

Dr. Stephanie received her Bachelor of Science (Maj. Vet tech) from the University of Queensland, Australia, in 2006. After graduation, she moved to the other side of her beautiful, sunny country, to the most isolated city in the world (Perth, Australia), to begin her veterinary degree at Murdoch University. 5 years later, she received a dual degree in Veterinary Biology and Veterinary Medicine and Surgery.

After all this schooling, Dr. Stephanie packed her things, her beloved Labrador & fluffy cat, and made the big move to the USA. She lives and practices at a clinic in the “big apple.”

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