Thousands of Pet Owners Say Popular Flea Collar Linked To Over 1700 Pet Deaths


A joint report from USA Today and Investigate Midwest is questioning the safety of one of the most popular flea collars on the market. The news article has noted that the Environmental Protection Agency has received 75,000 complaints from pet owners about the Seresto Flea and Tick collar in the past few years. The report also indicates there have been nearly 1,700 pet deaths linked to the collar.

Many pet owners that have voiced concerns over the collars are reporting their dogs developed alarming skin rashes and other skin problems after wearing the collars. Other pet owners have said their dogs have died as result of toxic reactions to the chemicals found in the collars. There have also been 1,000 incidents involving human harm.

“The EPA appears to be turning a blind eye to this problem, and after seven years of an increasing number of incidents, they are telling the public that they are continuing to monitor the situation,” Karen McCormack, a retired EPA employee who worked as both a scientist and communications officer, said according to New York Daily News.

Seresto collars use the chemicals Flumethrin and Imidacloprid, which are pesticides that target fleas and ticks. Imidacloprid affects the central nervous system of fleas and is a member of the neonicotinoid class of insecticides. Flumethrin repels and kills ticks and is a pyrethroid class. Although the two chemicals act in different ways to attack the pests, the EPA has not yet studied how the two chemicals interact with one another, as noted in their bulletin “Weighing Risks to Children from Dogs Wearing Seresto Collars“.

In scientific studies, skin lesions in dogs appear to be related to dosage amounts of flumethrin. “In toxicity studies, dogs (Beagles) were fed flumethrin mixed with food at 25, 50, 100 and 200 mg/kg feed during 13 weeks. At the end of the study all dogs showed skin lesions (thickened skin covered with hyperkeratotic material) at doses >50 mg/kg feed. The NOEL (No Observable Effect Level) was 25 mg/kg feed, equivalent to 0.88 mg/kg bw per day,” writes


There is also evidence that cats are more susceptible to synthetic pyrethroids than dogs, reveals. “Cats may not tolerate doses of flumethrin that are harmless for dogs. This is associated with glucuronidase deficiency in cats, the enzyme responsible for breaking down most synthetic pyrethroids in the organism in a process called glucuronidation. As a consequence, synthetic pyrethroids remain much longer in the cat’s organism than in dogs or other mammals.”

This is not the first time flea collars have come under scrutiny for the chemicals they use and how they may harm pets and children.

In 2012, France banned numerous collars following concerns that chemicals contained in the products pose a risk to children’s health. France’s veterinarian medical ruling body recalled 76 products after French scientists studied three cases where children may have absorbed diazinon (also known as Dimplylate, a chemical used in WWII as a nerve gas) through their skin after hugging and sleeping with their pets. Poisoning with the toxin can cause symptoms of headaches, dizziness, blurred vision, vomiting, nausea, loss of co-ordination, diarrhea and muscle-twitching. The ban affected any anti-parasitic collars containing dimpylate (diazinon) along with propoxur or tetrachlorvinphos.

Propoxur and Tetrachlorvinphos have been linked to adverse effects to prenatal development and potential nerve damage to children as well as potentially causing cancer.

In the years since France’s ban, various environmental protection agencies and governmental health authorities in other countries have banned dimpylate from being used in collars. There are also numerous studies on the use of the chemicals propoxur and tetrachlorvinphos. However, despite increased findings that both chemicals are potentially dangerous for pet and human health, many flea collars containing these chemicals are still sold on market today.

The video below from the Canadian news TV show CBC Marketplace investigated the controversy surrounding flea collars back in 2014.

The reporters also did a harmless test to see how easily the pesticide chemicals from a flea collar can spread over surfaces of your home – couches, clothes, carpets, toys. This is where the danger from flea collars comes in. Residue from the collars can be absorbed or ingested by humans who touch it. It’s this exposure in the home that many scientists are concerned with. People nowadays are increasingly in close contact with their pets. Many people sleep with their cat or dog and pets are allowed all over the home. Therefore, both people and pets are at more risk of absorbing the chemicals emitted by flea collars.


The chemicals in Seresto collars – Flumethrin and Imidacloprid – can act neuropathically if pets or people are exposed to them in high amounts. It is important that you purchase the appropriate size collar for your dog’s weight class and follow the instructions of the manufacturer and your veterinarian. For example, it should not be used in combination with other flea and tick treatments as you may accidentally overdose your pet.

The majority of adverse reactions reported to the EPA appear to affect the skin. People who complained to the EPA noted that their dogs develop skin irritations and/or skin lesions around their necks accompanied by itching, red skin, blistering and loss of hair.

So what are the toxic symptoms to look out for in your dog that may indicate he or she is having an adverse reaction to a flea collar?

A dog will most likely develop a reaction a few hours after exposure. If you note your dog developing a rash around his/her neck, remove the collar right away and wash the dog’s fur.

More serious effects of overdoses or adverse reactions to these chemicals include:

  • Ataxia (uncoordinated movements)
  • Cramps or spasms
  • Hyper reactions – exaggerated reactions to noises, movement, touch etc.
  • Body tremors
  • Lethargy or fatigue
  • Drooling
  • Vomit
  • Diarrhea
  • Urinary incontinence

Affected pets can also develop:

  • Difficulty breathing
  • Disorientation
  • Fever
  • Hypothermia
  • Cough

Parasitepedia indicates that young animals appear to be more sensitive to overdosing and react stronger to toxicity. However, symptoms will depend greatly on what product is used, the dose, and what kind of exposure that occurs. For instance, have they ingested it, inhaled it, or had it applied to their skin?

So should you continue to use a flea collar or abandon it all together? There are many risk factors to consider. Firstly, veterinarians point out there are other flea and tick preventative products on the market nowadays that make flea collars unnecessary. These include topical or oral treatments. Please discuss these options and the potential side effects for your pets with your veterinarian.


Also, it is important to educate yourself as to the parasitic risks in your community. Do you live in an area with a high tick population that carry disease (Lyme Disease, Rocky Mountain Spotted Fever or others)? If you do, then parasite prevention is strongly advised.

If the tick population in your area is low, then maybe you only need a treatment that focuses on flea prevention. Read our article How to Treat and Prevent Fleas From Infesting Your Dog.

You and your family will need to weigh the risks of pet’s exposures to pesticides from anti-parasitic prevention products against the risks of infestation and potential disease they (and you) may get from fleas and ticks. Be sure to consult with your veterinarian if you have questions or concerns.

Note, if you live in the United States you can report adverse incidents caused by the use of pest collars here.

Also, several readers have indicated that there are counterfeit flea collars that imitate Seresto’s in the market. Please make sure your purchases are from known retailers.

The content in this article is not intended to be a substitute for professional veterinarian or medical advice, diagnosis, or treatment. Always seek the advice of your veterinarian or other qualified health provider with any questions you may have regarding a pet’s medical condition.


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