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1,698 Pet Deaths — Why Is the EPA Turning a Blind Eye?

This popular product tops the list of incidents involving pesticide pet products, so why haven't you been warned that it could kill your dog or cat - or even harm you? The company has unabashedly been selling them since 2012, and the EPA continues to deem them 'eligible' for registration.

bayer seresto collar


  • A major expose by the Midwest Center for Investigative Reporting and USA Today is raising awareness about the potential toxicity of the hugely popular Seresto flea and tick collars for pets
  • Despite 75,000 incident reports since 2012, including almost 1,700 deaths of animals and 1,000 incidents involving harm to humans, the EPA has done nothing to inform the public of the possible risks of the product
  • In mid-March, a U.S. Congressional subcommittee demanded a recall of the collars; the manufacturer, Elanco, is refusing to conduct a voluntary recall
  • Unlike other flea/tick collars, the Seresto collar contains two pesticides; the synergy of the two chemicals appears to make them more effective, but also more potentially toxic to both pets and people

Editor's Note: This article is a reprint. It was originally published April 18, 2021.

Just as warm weather is arriving and bringing fleas, ticks and other pests with it, there’s breaking news that one of the most popular pesticides for dogs and cats, the Seresto flea and tick collar developed by Bayer and sold by Elanco (it’s the #1 selling collar on Amazon), is potentially lethal.

According to U.S. Environmental Protection Agency (EPA) documents,1 as of June 2020 the agency had received 75,000 incident reports about Seresto pet collars since their introduction in 2012, including 1,698 deaths of animals and nearly 1,000 incidents involving harm to humans.2

Is the EPA Giving the Seresto Collar a Pass?

A March 2 report by the Midwest Center for Investigative Reporting and USA Today points out that the EPA, which is in charge of regulating products containing pesticides and has known about the incidents for years, has done nothing to inform the public of the risks of the product.3 Retired EPA employee Karen McCormack, who worked as both a scientist and communications officer, said Seresto collars top the list of incidents involving pesticide pet products.

“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,” McCormack said. “But I think this is a significant problem that needs to be addressed sooner rather than later.”4

It seems Elanco disagrees. Keri McGrath, a spokeswoman for the company, told the New York Post via email that more than 25 million Seresto collars have been sold since 2012. Incidents reported in 2020 amounted to “a fraction of 1% of users,” defined by the World Health organization as “uncommon,” according to McGrath.5

“It is critically important to understand that a report is not an indication of cause,” she wrote. “What those numbers represent is the number of reports received, and do not reflect causality.”

The EPA is shrugging off the issue as well. “No pesticide is completely without harm,” according to an EPA spokesperson. The agency has found the Seresto collars “eligible for continued registration” according to the USA Today report.

“EPA ensures that there are measures on the product label that reduce risk,” the spokesperson added. “Some pets, however, like some humans, are more sensitive than others and may experience adverse symptoms after treatment.”6

However, in a decidedly strange statement to the New York Post, the EPA appears to admit to a lack of focus in recent years:

“Under the Biden-Harris Administration EPA has returned to its core mission, which includes protecting our pets’ health,” the statement said. “We take every incident reported seriously and review these data to see whether action is necessary.
EPA encourages pet owners to read the entire label before using the pesticide product and follow all directions carefully, including monitoring your pet after application to see if side effects occur. If side effects develop, the label tells the consumer to consult the pet’s veterinarian immediately.”7

Congressional Subcommittee Demands Recall

According to news items published on March 19, a Congressional subcommittee on economic and consumer policy is now demanding a recall of the collars. Per the New York Post:

“In a letter to the manufacturer of the Seresto collar — a top seller on Amazon and at major US pet retailers — US Rep Raja Krishnamoorthi (D-Ill.) demanded an immediate recall, citing reports that it has been involved in 75,000 harmful incidents to pets and nearly 1,000 incidents involving humans, according to data from the Environmental Protection Agency.”8

In the letter, Krishnamoorthi states that members of the subcommittee believe the actual number of injuries and deaths is much larger, “since the average consumer would not know to report pet harm to EPA, an agency seemingly unrelated to consumer pet products.”

Nathan Donley, a senior scientist at the Center for Biological Diversity and an expert on U.S. pesticide regulation, agrees the number is most likely an undercount and “the tip of the iceberg.” To report an incident, a person first has to make the connection between the collar and the problem their pet is having. Then they also have to figure out who to contact and how to make a report.

“Most of the time, people are not going to make the connection or they’re not going to take an hour or so out of the day and figure out how to call and spend time on hold,” Donley told Midwest Center for Investigative Reporting and USA Today.
“My God, if this doesn't trigger a concern, that's a fundamental problem with the process. The fact that EPA has not done anything to alert the public that there might be an issue here, it strikes me as bordering on criminal. The EPA has this system in place to compile information and it’s just collecting dust in some database.”9

In addition to a recall and customer refunds from Elanco, the subcommittee is asking Bayer to release information about the product’s toxicity and is investigat­ing all communications between Bayer and Elanco (which bought Bayer’s animal health division last year) regarding “toxicity or risks of death and injury to pets or humans from Seresto flea and tick collars and the transfer of liabilities.”

In response to the Congressional subcommittee letter, Elanco stated that it is backing the safety of its Seresto collar, that no market action is warranted, and that media reports on hundreds of pet deaths are based on “raw data.” According to Tony Rumschlag, senior director for technical consultants at Elanco, "Thorough investigation of available data has shown no established link between exposure to the active ingredients in Seresto and pet deaths.”10

A ‘Really Nasty’ Combination of Two Pesticides

In the letter to Elanco, Krishnamoorthi points out that the Seresto collar is the only pest control collar that contains two pesticides — imidacloprid and flumethrin — which may make it more effective, but also more toxic to both pets and people.

Imidacloprid is a neonicotinoid insecticide, which is the most commonly used insecticide on crops in the U.S. Neonicotinoids are linked to massive die-offs of bees, butterflies and songbirds, but the EPA proposed re-approving imidacloprid last year. In the European Union, the pesticide is also allowed in pet collars, but is banned for outdoor use. Along with growing evidence that mammals can also be harmed by these pesticides, they are also harming the environment.

The other active ingredient in Seresto collars, flumethrin, is used only in that brand collar, according to EPA documents.

Most studies on pesticides that are ultimately used to support the registration of products with the EPA, are conducted by the manufacturers of the products. In the case of Seresto collars, it was Bayer, and the majority of their studies looked at the pesticides individually, not in combination.

However, according to the Midwest Center for Investigative Reporting/USA Today report, a 2012 Bayer study found the two chemicals have a “synergistic effect,” meaning they’re more toxic when used together. This “unique pharmacological synergism” can work in as little as six hours to prevent ticks from attaching and feeding, according to the study.

Eight more companion animal safety studies by Bayer were also conducted on Seresto collars, and the EPA used them to approve the product.

Donley (of the Center for Biological Diversity), who holds a doctorate in cell and developmental biology and is a former cancer researcher, believes this “synergistic effect” probably extends to pets. He’s unsure what makes the two pesticides so likely to cause harm but believes “it is clear something is wrong with the product.”

“You don’t even see these kinds of numbers with many agricultural chemicals,” said Donley. “For whatever reason, this combination is just really nasty.”

Safe, Nontoxic Alternatives to Chemicals

Among the many chemicals I advise trying to avoid are pest control products for pets, the most common of which are flea and tick preventives. Several times a year here at Mercola Healthy Pets and especially leading up to and during the summer months, I caution pet parents to use these products sparingly, or not at all if you can get away with it.

There are safe, nontoxic alternatives for pest control for pets, and they don’t have side effects, unlike virtually all forms of chemical pesticides. I recommend common sense, first and foremost. Do you apply chemicals to your human children every time they walk in the woods? I recommend you use the same level of concern and vigilance for all family members.

If you live in a high-risk area and do apply pesticide sprays on your kids, your pets probably need them too (a pet version). If you rely on meticulous tick checks after your children have been in high-risk areas, include your pets in the body search for unwelcome parasites (and complete a 4DX or Accuplex test at least annually if you live in a tick-endemic area).

Many people rely on safer repellents for their human family members when enjoying the great outdoors. There are also safer alternatives for pets:

  • A safe, natural pest deterrent
  • Cedar oil (specifically manufactured for pet health)
  • Natural, food-grade diatomaceous earth, topically (not on the face)
  • Fresh garlic (¼ teaspoon of freshly chopped garlic per 15 pounds of body weight once daily)
  • Feed a nutritionally optimal, species-specific fresh food diet to bolster your pet’s innate immune defenses
  • Bathe and brush your pet regularly and perform frequent full-body inspections to check for parasite activity (if your dog or cat spends a lot of time outdoors, it's important to check your pet and yourself for ticks every night during tick season)
  • Use a flea and tick comb to naturally exfoliate your pet's skin while removing or exposing pests (absolutely nothing takes the place of physically checking for ticks)
  • Make sure both your indoor and outdoor environments are unfriendly to pests

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