Cat Flea Collars - Cat Info Detective

Cat Flea Collars

Skye Blake-updated, white background

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

Every once in a while, we hear of alerts about cat flea collars and the pesticides used in them.

paw prints coming in from a distance

The information here is for general knowledge… always see your vet with questions about your cat’s individual needs. 

Who Is Skye Blake?

Skye Blake-updated, white background

Skye Blake, Cat Info Detective, is a curious cat researcher (not a veterinarian) who sniffs out expert, reliable sources about cats, studies their information, then passes it on to you! 

Sometimes there’s not enough evidence for easy answers, so Skye gives you all sides, explains the situation as thoroughly and clearly as possible, and links you to experts on each page. 

All sources are at the bottom of each page so you can do more snooping. 

Seresto® Flea Collars

Curious long haired tabby

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…

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. 

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

This is important to emphasize, since the normal assumption is to think it’s for a year or even a month.

Second, the article raises questions that need answers.

Is There Proof?

Tuxedo cat sitting on walkway wearing collar

Is there proof these injuries/deaths were caused by pesticides in the collar?

The answer so far is “no”.

Both the article and the EPA document give no links or direct evidence about specific claims.

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

siamese wearing collar

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, there are no answers to questions raised about other possible issues involved in these situations.

Did the Owner Follow Directions Properly?

Balinese cat sniffing a finger (wearing a collar)

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

It’s important for people to monitor flea collars for fit and other factors.

Treat collars as you would medication… carefully and strictly according to instructions.

Seresto® collars should not be in water.

Did the Owner Use the Correct Collar?

Tabby/white cat outside scratching chin; fleas, collar

Don’t use a dog collar (even a small one) on a cat.

Sometimes people think they can use a small dog flea collar on a cat since it will fit a larger cat.

This is dangerous because dogs and cats process pesticides very differently. What may be harmless for a dog can kill a cat.

Was It a Real or Fake Seresto® Collar?

grey cat statue; fake or real flea collars

Fake collars are a real problem!

They look like the real thing but can have different pesticides (or none at all). Safety is not a priority for these companies.

These come primarily from mainland China and Hong Kong.

ragdoll cat wearing a collar

Fake collars can be difficult to spot so the best way to avoid them is to buy only from reputable dealers 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, it’s 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; flea collars

Check out these videos to discover more about spotting fake cat flea collars…

“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

Were There Underlying Health Problems?

veterinarian listening to a cat's heart

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

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.

abyssinian kitten on a blanket

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.

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.

woman hugging cat

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

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

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

Are the Active Ingredients in Seresto® Collars at Fault?

ragdoll cat wearing a collar

The active ingredients in Seresto® collars are Flumethrin 4.5% and Imidacloprid 10.0%.

This is an important question that can only be answered by further study in a controlled environment.

It also opens up a few more questions…

calico cat wearing collar
  • If these ingredients are at fault, is it just one or a combination of the two?
  • Is it some combination of the active and inactive ingredients?

These questions about flumethrin and imidacloprid can’t be currently answered because no real evidence has been shown 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.

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

Ginger tabby kitten sleeping

“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

black cat watching prey intently; not wearing flea collar

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.

Discover more at “Cat Health“.


Sources used on this website are either primary or secondary. 

Primary sources are always preferable and have the most reliable information because they’re 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.

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

Updated April 14, 2024

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