Toxicity of Flea & Tick Treatments for Cats: What Every Cat Owner Should Know

by Monika
Toxicity of flea and tick products

Recently, I saw so many disturbing and heartbreaking posts about flea treatments, dips, baths, shampoos killing cats or causing severe mental issues, that I had to write this post. Hopefully, it will help spread the word and motivate people to do more research before buying over-the-counter flea products in stores.

It is so easy to hop on to Amazon or the local store and pick up the cheapest or the first flea product you see. Who would have ever thought something sold in stores can be toxic and harmful while its primary purpose is to help your pet! So thousands and thousands of people buy cheap over-the-counter flea products trusting the stores and the manufacturers that their product is good for pets. And, a lot of those people end up regretting their worst purchase in life that killed their pet or poisoned them resulting in negative consequences for days or even weeks. I can only imagine how awful and guilty those pet parents must feel. But it is not their fault. They didn’t know. Only after they had this awful negative experience, they learn about the toxicity of over-the-counter flea medications from their vet, with an enormous vet bill.

Flea products carry not only a risk for your pet but also humans that come in contact with the flea shampoo, collar or other flea products. If you have a toddler, they are at even higher risk from such products.

Most of the data in this post is from the NRDC document Poisons on Pets: Health Hazards from Flea and Tick Products (2000).

What is toxic in flea and tick treatments?

Adverse effects of flea and tick products on pets - table

According to NRDC, organophosphates are the ones to blame for the toxicity of the flea products. Organophosphates are a group of chemicals most commonly used as insecticides. NRDC listed some harmful insecticides (which fall in the group of organophosphates) and the products that contain them in their document.

These are some of the compounds you should avoid in flea and tick products:

  • Carbamates
  • Pyrethrins and pyrethroids
  • Phosmet
  • Diazinon
  • Tetrachlorvinphos
  • Fenthion
  • Permethrin

See page 50-52 of NRDC document for a more detailed list.

Signs of poisoning in cats

Cats are more vulnerable than dogs to poisoning from flea and tick treatments. This is presumably due to their smaller size relative to dogs, their grooming habits (frequent licking of fur), and their absence of enzymes needed to detoxify certain organophosphates, according to NRDC.

Some signs of OP poisoning in cats are

  • watery eyes,
  • lack of appetite,
  • excessive salivation and urination,
  • nervous signs such as tremors,
  • behavioral changes such as hyperactivity.

But often, the signs are too subtle or atypical to connect it to poisoning so pet owners can’t easily know that their pet is poisoned.

Least toxic approach to getting rid of fleas

Before you treat your cat for fleas, NBCP suggests you first try non-toxic options for getting rid of fleas.

First, examine your pet to make sure they do have fleas. If they are scratching, it doesn’t necessarily have to be because of the fleas and ticks. Only after you are sure that your pet has fleas, you can start with the measures to get rid of the pests.

And yes, this non-toxic approach will be more time-consuming than a regular flea bath, but if it can help you avoid using harsh flea and tick treatments on your fur baby, it is worth it.

Sometimes, basic physical measures are enough to get rid of the fleas. So try this first:

  • Bathe your pet with a regular cat shampoo (or a dog shampoo if you are treating your dog). Sometimes, this might be enough to get rid of the fleas.
  • Use a flea comb to get the fleas out of your cat’s fur. Do this outside if you have a fenced yard so that the fleas don’t stay in your home, or dip the comb in a bowl of water after you get the fleas out of their fur, so they don’t jump back.
  • Vacuum the entire house and wash the cat’s bedding.
  • You can limit your pet’s outdoor time until you get rid of the flea issue.

These are cheap and non-toxic options that can help if you have a mild flea problem.

NRDC mentions prevention with insect growth regulators as a safer alternative. Insect growth regulators and insect development inhibitors stop the next generation of fleas from growing. I have none experience with those types of products, but I suggest you ask your vet about it if you think this could help in your situation.

If the fleas got out of the hand and you feel you must use a flea product, look at page 43 to see the list of safer flea and tick products for pets. But, again, I suggest you consult with your vet before doing any kind of purchase.

I might be too cautious about everything. But I think it’s better to be on the safe side and annoy your vet with too many questions than to buy a product that is not good for our cats. Keep in mind that this document and table of products is from the year 2000. There might be less-toxic products on the market now. I’m sure your vet can recommend one.

What to take from this

If there is something you should take from this post, it should be this:

  • Never use products intended for dogs on cats.
  • Make research before you buy any flea product and check with your vet to make sure the product will not hurt your cat.
  • Avoid using products containing toxic pesticides such as the ones listed in the document, page 50-52.
  • Follow the exact instructions on any product you use. Many cats were poisoned or even died because their owners applied too much of the product.

This post is just a preface to everything that should be known about the flea and tick products and there isn’t much info on this topic out there. All I could dig out is a great document from NRDC: Poisons on Pets: Health Hazards from Flea and Tick Products from the year 2000. So even if that document contains a bunch of valuable info, there are now new products on the market and new dangers.

Do your own research before buying any pesticide-based products for your cat. The one thing that worries me the most is that those harsh products we apply to our pets don’t even have to be tested for toxicity or potential dangers they carry before putting them on the market. Plus, the long-term consequences were never studied and we can only hope it won’t result in something bad for our pets and us.

Do you use over-the-counter flea and tick products? Do you worry about their effect on your cat?

Let me know in the comments!

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Marjorie at Dash Kitten May 2, 2018 - 11:36 am

Our friend Timmy Lipenda was damaged by over the counter flea dedication (deliberately before he was adopted). Cheap OTC medicines are often lethal and, as you say, you need to check the ingredients carefully. We would only but the safest flea treatment from our veterinarian when we need them. Oddly enough curling hot summer has doe away with a lot of our flea problems (heat stroke for fleas?)

This is a valuable post that will help cat owners figure it what is safe to give their cats. Well done.

Monika May 3, 2018 - 9:05 am

Deliberately damaged? Oh my, who would do such a thing! I am lucky too when it comes to fleas, Okica didn’t get them.

Holly May 2, 2018 - 12:15 pm

I wrote on the same subject with a different twist (runs tomorrow). I have a house full of cats and when we get fleas it is a huge pain. Cats are inside only but we live in the woods, the driveway is sand, and I groom cats… fleas are a thing. I use advantage and it has worked well for us and no one has reacted badly. I used a cheap thing once upon a time when I was young and dumb and one of my cats had a bad reaction but thankfully recovered without incident. I learned!

Monika May 2, 2018 - 1:22 pm

Yes, Adventage is listed as a safer product for getting rid of fleas in the document I was referring to in my post. Fleas are such a pain in the butt! I can’t believe our Okica never catches fleas, and she has access to the yard. I must be one lucky human!

Kelly May 2, 2018 - 2:37 pm

Fortunately my cats have not been infected with fleas. I have however heard of and read about medications, not only for fleas, being bought over the counter or on the internet that are not safe or even recommended for cats/pets. I can see that some may think they are getting a deal on meds, but I prefer when it comes to my pets health and safety, to check with my vet before applying or giving my pets meds.

Monika May 3, 2018 - 9:01 am

I agree. It’s always best to check with the vet to be on the safe side 🙂

Hindy Pearson May 2, 2018 - 3:25 pm

Wow it’s quite scary to learn how toxic these commonly used products can be. Personally I like natural products when possible, and have tried them on one of my dogs. Unfortunately he is resistant to any treatment I’ve tried, and the last thing I want is a third flea infestation. He wears a Soresto collar, and while it’s not my preferred method of flea control, so far it’s the only thing that has worked.

Amy Shojai, CABC May 2, 2018 - 4:45 pm

This is very important information, so am glad you’ve written about it. Flea problems vary depending on geographic region, too. Her in Texas, a bath and flea comb wouldn’t help–but in other areas (Colorado mountains for instance) there might be no fleas at all. And yes, when you also have dogs it’s important to keep the cats AWAY from a treated dog for a period of time, just in case of potential toxicity to the cat. These days, many of the formerly Rx-only flea products now are over-the-counter (or online and counterfeit) so being careful is a must!

Seville at Nerissa's Life May 2, 2018 - 7:04 pm

Peep #1 ALWAYS gets our monthly dabbin’ treatments from our doctor ’cause so many kitties have been harmed by the over-the-counter stuff. She would never, ever trust anyone but a medical professional when buyin’ the product. purrs

PS. I’ve been tryin’ to convince her that replacin’ the lawn with catnip is the answer to keepin’ fleas out of the yard. So far, she’s not buyin’ it. MOUSES!

Julia Williams May 2, 2018 - 7:04 pm

When I was living in CA, fleas were a HUGE problem. Natural remedies were not enough, and I had to resort to topical Advantage. I didn’t really want to, but felt I had no choice as I couldn’t eradicate them. Now I live in Montana and have only had very minor flea issues which I take care of by combing, and combing and combing….and diatomaceous earth. Thanks for this informative post and for educating people about the dangers of OTC flea products.

Monika May 3, 2018 - 9:00 am

There are always some extremely harmful products, but also products that are considered fairly safe. If a flea treatment is unavoidable, it is important to do the research and choose the safest product 🙂

Ruth Epstein May 2, 2018 - 7:19 pm

Fantastic post with some really good points to learn from. I do not have cats at the moment but remember mine getting fleas and it was a nightmare. Today it is only Layla

Sadie May 2, 2018 - 8:50 pm

It’s scary, and maddening that such toxic products are advertised as beneficial, and made readily available to consumers who have not done their research. It’s also very sad that individuals are not able to put their trust in some of the companies supplying pet products. Thanks for generating awareness.

Gail M Akeman May 2, 2018 - 11:30 pm

I did not know about this. Many chemicals can be toxic for our pets. We all have to pay attention.

Jana Rade May 3, 2018 - 1:45 am

I am paranoid about these things enough having dogs. If I had cats, I think I’d lose it with worry. The upside is, that the rule of thumb is that if something has proven safe for cats, it should definitely be safe for dogs baring the possibility of an individual allergy.

Christine AnimalHealer May 3, 2018 - 1:46 am

It’s not just over the counter flea and tick products that are harmful to cats (and dogs). Prescription prevention products can cause serious like seizures, tumors, long term illness and even death. It’s criminal that these products are allowed to be sold by vets, who pet owners trust. The scary warning label alone should be enough to alert people that these products are not safe. I wish more people knew of the safe alternatives that myself and other holistic animal healers teach our clients and customers.

Monika May 3, 2018 - 8:56 am

What’s even worse, many products don’t even have a warning label. That’s why it is important to educate people about the potential dangers.

Sweet Purrfections May 3, 2018 - 2:34 am

I’ve read about many sad situations when people have purchased and applied flea/tick products from OTC. My girls are on a monthly topical treatment. I know I’d rather avoid chemicals on them, but we live in the South where fleas/ticks and mosquitoes are numerous.

Bree May 3, 2018 - 3:47 am

Omg what a great post! This is so important to read/know for EVERY pet owner. I would have actually never thought about this. So I will definitely be more careful now. It’s truly horrible that dangerous chemicals are being sold in products we need to use! Thanks for sharing.

Megan June 3, 2018 - 11:19 pm

The effects of some OTC products can be devastating. Not to mention their lack of efficacy. Vet products may seem to cost a tiny bit more up front, but they will save a ton of money, heartbreak, and will actually safely take care of the problem in the first place.

Monika June 4, 2018 - 8:47 am

So true! It’s always better to invest a bit more in a high quality product, especially when that product affects our cat’s health.

Dawn Gowgiel May 5, 2020 - 12:57 am

Just because it is a high quality product and purchased from a veterinarian, doesn’t necessarily mean that it is safe! They all contain a combination of the same active ingredients which may or may not harm your pets, depending on your pet’s sensitivity to the chemicals used. Some chemicals aren’t safe for any animal, as indicated in the NRDC report referenced in your article. Some are listed as relatively safe, but may not be safe for your particular pet. I used Vectra and Revolution (at different times) on my cat, both prescribed by& purchased from my vet. My cat never liked when I applied Vectra and acted like it was hurting his skin. However, sometime during the second season of using it, he developed a severe reaction immediately after application: crying, drooling continuously, lethargy, acting extremely fearful & hiding under furniture. I thought I killed him, but thankfully the symptoms gradually went away over the next 24 hours. I told the vet & she said I must not have applied it correctly & that my cat must have licked it. I knew that I applied it right, but I listened to my vet & applied it again the next month, being extra careful. Guess what – same immediate reaction & my cat had no opportunity to lick the stuff!! Stopped using it & the next year I told my vet about it again, so she prescribed Revolution. I bought it from her and put it on my cat – same horrible reaction, so I never used that again. The next year I tried Wondercide (seen on Shark Tank & had tons of great reviews) – it worked great and thought I had finally found a non-toxic solution for my cat! The following year I put a small amount on my cat (one small squirt on my hand, rubbed my hands together, then rubbed lightly over my cat’s back) – within seconds, my cat developed the same severe reaction that he had from Vectra & Revolution. My cat must be extremely sensitive to all chemicals, so I don’t know what to do now. He is an indoor cat, but loves going outside on a leash daily. So a word to the wise: all cats/dogs/humans are different and what works for some, definitely doesn’t work for all. Be cautious when using any chemical – either on your pets or on yourself.

Monika June 3, 2020 - 2:55 pm

Oh no, that sounds horrible. So sorry you and your cat had to go through this so many times. I actually started using diatomaceous earth lately. My cats luckily don’t get fleas but they do get ticks and it works well for now. Although for people with bigger flea and tick problems, that would probably not be effective enough.


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