Cat Flea Collars - Cat Info Detective

Cat Flea Collars

Skye Blake looking left through magnifying glass

Greetings concerned cat lovers! Skye Blake here, reporting in about cat flea collar alerts…

Every once in awhile alerts are put out about cat flea collars and the pesticides used in them.

paw prints coming in from a distance


We’ll start with claims in a USA Today article that Seresto® cat and dog flea collars are hurting and killing pets, and even causing health problems for people.

This bears further investigation so I’ve snooped around and here’s what I’ve found…

Curious long haired tabby

This claim is based on U.S. Environmental Protection Agency statistics, and while they certainly look alarming, they don’t give the full picture.

Statistics are like the outline of a picture. You need to fill it in with detailed evidence to make the picture complete and accurate. 

outline of a walking cat

First, the EPA statistics cover the 8 1/2 years (1/1/2012 – 6/16/2020) that Seresto® has been sold.

This needs to be emphasized since the normal assumption is to think it’s for a year or even a month.

Second, there are questions raised that must be answered to fill in the picture…

Is there any evidence that proves these deaths or injuries were caused by the pesticides in the collar?

Tuxedo cat sitting on walkway wearing collar

The answer so far is “no”.

No links or direct evidence are given in the article or the EPA document about specific claims.

More often than not, people assume the collar is at fault without considering other possible factors.

They then write reviews or make official complaints without actual facts.

This is a major problem because there aren’t enough facts to make any genuine, helpful conclusions.

Without these facts, questions are raised as to other possible issues involved in these situations.

Did the pet owner follow the directions properly when using the collar?

Balinese cat sniffing a finger (wearing a collar)

Flea collars need to be monitored for fit and other factors.

Seresto® collars should not be in water.

They should be treated as you would medication… carefully and strictly according to instructions.

Did the pet owner use the correct collar?

Tabby/white cat outside scratching chin

Using a dog collar (even a small one) on a cat is dangerous because the dosage is made for how a dog’s body handles pesticides, not a cat’s.

Was it a real or fake Seresto® collar?

grey cat statue

Fake collars are a real problem since they are made to look like the real thing but can have different pesticides (or none at all) and are not made with safety in mind.

They come primarily from mainland China and Hong Kong.

Fake collars can be difficult to spot so the best way to avoid them is to buy only from reputable dealers (Chewy, Amazon, etc.) or through your veterinarian.

The easiest way to spot them is the price. The real collars are $55-60, so if it’s online a lot cheaper, its a fake.

The other big clue is that fake collars don’t work against fleas and ticks… but you’d find that out too late.

Dark tabby cat scratching his face while standing

Find out more about spotting fake cat flea collars at these YouTube videos…

How to spot a fake Seresto® collar, by Complete Care Animal Hospital, 10/5/2020

How to Tell if your Seresto® Cat Collar is REAL vs. FAKE – 2020, Mocha and Cinna Meow Boys, 9/1/2020

Did the animal have underlying health problems, like diabetes, thyroid, kidney, liver or heart disease?

veterinarian listening to a cat's heart

Without a necropsy (animal autopsy) and toxicology tests, we can’t know if there was a problem that made the animal susceptible to reacting in ways that a healthy cat wouldn’t, especially in senior kitties.

If toxicology tests and a necropsy had been performed on each animal where a claim was made, there would be actual evidence to show what caused the death or injury.

We could then have a more complete picture, identify the true problems, and find solutions.

abyssinian kitten on a blanket

In some complaints of human illness, the person petted, kissed or slept in the same bed with a dog or cat that was wearing the Seresto® collar.

Either immediately or at a later time they had skin rashes, breathing problems or other symptoms.

The only evidence given is anecdotal, not confirmed by scientific tests…

…In some cases symptoms lessened or went away when the collar was removed.

Are the active ingredients in the Seresto® collars at fault? (Flumethrin 4.5% and Imidacloprid 10.0%).

If so, is it just one or a combination of the two? Is it some combination of the active and inactive ingredients?

ragdoll cat wearing a collar

These questions about flumethrin and imidacloprid can’t be answered because no real evidence has been shown yet that they’re causing the problems.

What can we conclude at this point?

Dark tabby in hay ready to pounce

As you can see, there are too many assumptions and unanswered questions.

The main one is “what’s the scientific evidence that confirms the claims?”

Until the claims are proven, no steps can be taken to properly fix anything.

Ginger tabby kitten sleeping

A veterinarian interviewed in a Yahoo! Daily Paws article stated the only real conclusion we can draw.

“My takeaway is that it should be looked into,” says Elizabeth Trepp, DVM. “I want to recommend the best safe products for my patients, and therefore as a vet I rely on agencies like the [Food and Drug Administration] and EPA to do their due diligence.”

More testing must be done and detailed facts gathered when incidents happen before concluding the product is the cause and should be withdrawn.

What You Can Do For Your Kitties


If you use Seresto® or other flea collars, you should talk to your veterinarian and make sure you’re using and maintaining the collars properly for maximum safety.

If you prefer to stay away from collars, there are other options available. Your vet can help you find what’s best for your kitties.

Check “Getting Rid of Fleas…For Cats Only!” and any of the related pages below for more information.

What Is a Flea? What Does It Look Like?How to Kill Fleas on Kittens, Senior & Sick Cats
Ways to Get Rid of Fleas on Healthy Cats!Is a Flea Treatment with Chemicals Safe for My Cat?
What Chemical Ingredients Are in Flea Products?What is a Natural Flea Treatment for My Cat?
Natural Flea Remedies You Can Buy Flea Control, the Homemade Way…
What Are Essential Oils…Do They Kill Fleas on Cats? What Is a Tick?
Getting Rid of Fleas…For Cats Only! Hot Cat Topics


Sources used on this website are either primary or secondary.  Primary are always preferable and have the most reliable information because primary sources are original and directly referenced. Scientific abstracts and data are good examples of primary sources.

Secondary sources, such as news articles, are weaker because they usually consist of opinions/assumptions that give no sources of their own, although sometimes they refer to primary sources. Thus, when I use secondary sources most are those with some authority, such as veterinarian or cat behaviorist books and articles.

List of Sources

Agents seize counterfeit cat and dog flea collars“, by News Staff, Updated: May 16, 2020 

Counterfeit and ‘potentially harmful’ Seresto® flea collars for pets seized in Pa.“, by John Luciew,, Updated May 18, 2020; Posted May 16, 2020

Did Seresto® Pet Collars Cause 1,698 Dog and Cat Deaths?” by Jordan Liles,, March 8, 2021

Dr. Elizabeth Trepp, Banfield Pet Hospital

“Popular flea collar linked to almost 1,700 pet deaths. The EPA has issued no warning.”, by Johnathan Hettinger, Midwest Center for Investigative Reporting, USA Today, March 2, 2021

“Seresto® Flea & Tick Collar for Cats”,

US EPA, Office of Chemical Safety and Pollution Prevention, Memorandum, “Flumethrin: Tier I Update Review of Human Incidents and Epidemiology for Proposed Interim Decision, by Shanna Recore, Industrial Hygienist, September 17, 2019

US EPA Office of Pesticide Programs Incident Data System, June 16, 2020

We Asked Vets About the Seresto® Flea Collars. Here’s What You Should Know”, Yahoo! News, Daily Paws, March 3, 2021

YouTube videos:

How to spot a fake Seresto® collar, by Complete Care Animal Hospital, 10/5/2020

How to Tell if your Seresto® Cat Collar is REAL vs. FAKE – 2020, Mocha and Cinna Meow Boys, 9/1/2020