Seresto Collars For Dogs: Are They Safe?

Seresto collars for dogs
Post At A Glance

If you use a Seresto collars for dogs … heads up! These collars are not safe! 

The internet and even mainstream press are buzzing with news about Seresto flea and tick collars. Reports say these popular collars are harming not just pets but even children. 

Even the US Congress has taken action to get the collars recalled. But that hasn’t happened because the manufacturer insists the collars are safe. So they refuse to take any action … even to warn pet owners about the risks. 

So if you use a Seresto collar on your dog, you need to know the truth about the risk to your pets and your family. 

What Are Seresto Collars?

Seresto collars for dogs are flea and tick repellent collars that stay on your dog 24/7. They’re odorless and water resistant (even after a bath). The collar lasts for 8 months, making it a very convenient option. It costs around $60, but you could pay a much steeper price … because it’s not safe for your dog or even your family

Seresto collars were created by Bayer Healthcare. Elanco Animal Health bought the company for about $7 billion in 2019. So Elanco now owns Seresto collars as part of that acquisition. And it’s a highly successful product for them. 

How Do Seresto Collars Work?

Seresto collars are impregnated with the active ingredients flumethrin (4.5%) and imidacloprid (10%). These ingredients release over your dog’s skin and coat during the 8-month period. The company doesn’t disclose the inactive ingredients so we don’t know what else is in the collars. 

Side Effects of Seresto Collar Ingredients

First, let’s look Seresto collar side effects. Here are the individual active ingredients. Imidacloprid and flumethrin are pesticide ingredients with known side effects. 


Flumethrin is a synthetic pyrethroid. That puts it in the same category as insecticides like permethrin.  Pyrethroids work by paralyzing the insects’ nervous systems. In mammals, flumethrin causes nausea, vomiting and seizures. 

In 1998, researchers fed Beagles food with flumethrin for 13 weeks. Some Beagles developed skin lesions, vomiting, weight loss and increased BUN (blood urea nitrogen) levels. Elevated BUN suggests possible kidney damage. These problems came up at the higher dosing levels. At lower levels, the dogs didn’t suffer side effects. 

RELATED: Learn why pyrethroids aren’t as safe as you think


Imidacloprid is a neonicotinoid insecticide. Neonicotinoids are widely used for crop protection as well as pet insecticides. Neonicotinoids are one of the main reasons for the loss of honeybees. And in dogs, Imidacloprid is known to cause problems like … 

  • Thyroid damage
  • Abortions and birth defects
  • Seizures and other neurological problems
  • Liver and other organ toxicity

Farm workers have experienced skin or eye irritation, dizziness, breathlessness, confusion, or vomiting from exposure to imidacloprid pesticides. Imidacloprid has caused skin irritation in pet owners after applying spot on products to their animals. It’s banned in the European Union for outdoor use. 

RELATED: Make your own safe flea and tick powder … 

Flumethrin and Imidacloprid Combined Are Riskier

The Seresto product registration document filed with the EPA warns that itching, slight hair loss and mild skin reactions may occur … but should go away after 2 weeks. And it warns children should avoid contact and shouldn’t play with the collars. Does this mean your child shouldn’t cuddle or snuggle with your dog?  Probably! 

The EPA has reviewed whether Seresto collars are safe to use around children. They say the collars may cause slight skin irritation but not skin allergies. They found that risks to children are “below levels of concern.” But then they admitted they didn’t review flumethrin and imidacloprid’s combined effects “because the two chemicals act in completely different ways.” 

So, that’s bit of a red flag, isn’t it? In fact, there’s research showing that the combined ingredients are more deadly to fleas. A 2012 in vitro study by Bayer reviewed how flumethrin and imidacloprid work together. The researchers stated (bold added for emphasis) …

“Thus, as we have shown here, the application of both compounds together leads to a much higher level of activity than either compound alone, which demonstrates that neonicotinoid insecticides (such as imidacloprid) acting on the nAChr and pyrethroid insecticides acting on voltage dependent sodium channels cooperate at the level of the insect nervous system to produce an enhanced sensitivity to the pyrethroid component, providing a way to obtain similar levels of pest control with a reduced dose of pyrethroid.” 

Does this mean this combination of ingredients could have a similar effect on your dog’s nervous system (or your child’s)?

It seems likely, given the number of complaints of neurological symptoms like seizures. So let’s look at that.  Research aside, what’s happening with Seresto collars in real life?

RELATED: Find out how flea and tick prevention products rank for safety

Seresto In The News

The sensational news reports started with a USA Today story that linked Seresto collars to almost 1700 pet deaths. The article reports that the collars may have caused “hundreds of pet deaths, tens of thousands of injured animals and thousands of injured humans.”  

Sadly, this isn’t just media hype. 

In 2021, the US House Subcommittee on Economic and Consumer Policy called on the manufacturer, Elanco, to temporarily recall its collar. The company refused.

In June 2022, after a 16-month investigation, the committee released a 24-page report titled: Seresto Flea and Tick Collars: Examining Why A Product Linked To More than 2,500 Pet Deaths Remains On The Market. The reported incidents involving Seresto collars now stand at 98,000 (up from 73,000). with 2,500 (up from about 1,700) pet deaths.

The subcommittee’s recommendations include …

  • Recalling Seresto collars
  • Canceling the collar’s registration
  • Strengthen the EPA’s scientific review process
  • Improve incident data collection

In California, a class action lawsuit was filed against Elanco, on behalf of individuals who’ve bought a Seresto collar for their pet since March 22, 2017. The action alleges that the company didn’t warn consumers of Seresto collar risks. The complaint states, “While the Seresto Collar Product is designed to harm and kill fleas and ticks, it is not supposed to harm and kill its wearers and their caregivers.” 

There are Facebook Groups about the harm Seresto collars do. Pet owners report serious problems like …

  • Seizures
  • Ataxia
  • Tremors
  • Lethargy/fatigue/depression
  • Lack of appetite
  • Diarrhea, vomiting, blood in stool
  • Skin problems
  • Vision problems
  • Hair loss
  • Tumors 
  • Death

Fake Seresto Collars

There are also problems with fake Seresto collars sold online. These have worse effects than the real ones, not surprisingly. So if you must use a Seresto collar, at least buy it from a reputable source, like a vet supply company.  Don’t buy from an unknown online source … and that includes Amazon and E-Bay, who have many behind-the-scenes sellers.

The Manufacturer’s Response

Elanco is sticking to its story. The CEO testified before the subcommittee, saying …

“No product is without risk. What matters is whether those risks are reasonable, in light of the benefits. Numerous studies and the incident report data for Seresto demonstrate the product does not pose an unreasonable risk.”  

Jeffrey Simmons, CEO of Elanco

Simmons has said Elanco would be wiling to work with the EPA on labeling, but not to recall the collars. Rep. Katie Porter replied, “With all respect, Mr. Simmons, it’s not your job to decide if the risk is reasonable. That’s the job of the regulatory body.”

Elanco claims that the rate of adverse effects is 17.26 per 10,000 sold in 2021. They say that most of the incidents are minor or moderate … and that there’s no link between the active ingredients and pet deaths.

It’s not surprising Elanco doesn’t want to recall the collars. Because Seresto collars are a blockbuster product. It’s Elanco’s biggest selling product worldwide. Seresto reportedly earned the company $64 million in 2020 4th quarter sales alone. That would translate to $256 million a year …  a lot of revenue to give up. 

And it’s not just Elanco who doesn’t want to acknowledge the reports. Vets love the collars too. And they’re speaking out to defend Seresto’s safety and efficacy. 

What Vets Say

Many vets are speaking out in press reports. They’re urging pet owners to remain calm. They say they’ve noted only mild side effects in the collars … like skin irritation around the neck.They’re also blaming the fake collars for the problems, recommending owners ensure they’re buying genuine collars by buying from veterinarians, reputable online pharmacies, or big box stores.

One vet commented in the Seresto Fake Collar Facebook group …

“You may be aware of the increase in reports of adverse reactions to Seresto collars. I reviewed VIN reports and there is legitimate concern that the reports are due to an increased flow of counterfeit collars from China.”

Here’s another reason vets love Seresto. They like pest prevention products that last a long time. That’s because they think we dog owners are a forgetful bunch and might miss a monthly spot-on treatment. The problem with this idea is … longer lasting protection means more toxic pesticides on your dog! 

Holistic Vets

You won’t find holistic vets endorsing Seresto collars. In fact, here’s what Dr Deva Khalsa said:

“Ticks and fleas are becoming resistant to these chemicals, and because of this, manufacturers are adding more potent ingredients, or combining a number of different toxic ingredients, to each dose of their products. The bottom line is that there is no chemical pharmaceutical flea and tick product, spot-on or otherwise, that does not adversely affect your pet’s health.

“I like to compare it to making your dog into a poison-soaked sponge. No matter if it is a flea collar, oral or spot on product, the ingredients circulate throughout the body, through all the organs … and there is enough poison in your dog’s arteries and veins to kill the parasites immediately

“Imagine you have cockroaches but you don’t want to spray because young children crawl around your floor.  So you take some sponges, soak them with cockroach killing liquid and leave them around the kitchen. Over the next few days, you find cockroaches several rooms away, feet up, all dead and crunchy – because they walked across those poison filled sponges. Tell me … isn’t this exactly what we’re doing with our beloved dogs?”

What Should You Do?

Whether Seresto collars caused the reported deaths and injuries or not, we do know the ingredients can be harmful to dogs (and cats)  … especially when they’re combined. Is it really worth the risk … when there are so many safe ways to protect your dog from fleas and ticks? 

If your dog (or cat) has a Seresto collar on now … consider taking it off! Return it to wherever you bought it and ask for a refund. Maybe your pet hasn’t had a reaction … yet. But that doesn’t mean he couldn’t get seriously ill in the future. 

If your dog has had a reaction to a Seresto collar, you should report it to the EPA at this link.

There are plenty of natural ways to prevent fleas and ticks on your dog. Switch to natural methods of pest prevention.  Here are some safe flea and tick repellent recipes you can easily make at home. 


Stanneck, D., Kruedewagen, E.M., Fourie, J.J. et al. Efficacy of an imidacloprid/flumethrin collar against fleas, ticks, mites and lice on dogs. Parasites Vectors 5, 102 (2012).

EPA Bulletin: Weighing Risks To Chilcren From Dogs Wearing SerestoTM Collars. October 2016 .

Stanneck, D., Ebbinghaus-Kintscher, U., Schoenhense, E. et al. The synergistic action of imidacloprid and flumethrin and their release kinetics from collars applied for ectoparasite control in dogs and cats. Parasites Vectors 5, 73 (2012). 

See AM, McGill SE, Raisis AL, Swindells KL. Toxicity in three dogs from accidental oral administration of a topical endectocide containing moxidectin and imidaclopri. Aust Vet J. 2009 Aug;87(8):334-7. 


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