Can Flea Collars Cause Seizures in Dogs?


Q:I have an older dog — a 10-year-old golden retriever — that I just adopted from a rescue. When I put a Seresto flea and tick collar on her, she started having seizures. She no longer has the collar but is now on phenobarbital to control the seizures. What do you advise using for flea and tick control on a dog that has a history of seizures? I know that the new pill is not advised for these dogs.

Kathy Waterhouse
Barrington, NH

A:You are not alone in your concern. There are a number of anecdotal reports online of flea collars causing seizures in dogs. But none of them is even remotely substantiated. The chances that a Seresto collar was the cause of the seizures in your pet are remote to nil.

Seresto contains two active ingredients: imidacloprid (an insecticide to kill fleas) and flumethrin (an insecticide/acaricide combination that kills fleas and also ticks). Both are very safe for dogs at the doses present in the collar and only very rarely cause adverse reactions — and not seizures. The most common reaction is dermatitis (inflammation of the skin) at the contact area. There have also been occasional cases reported of intoxication as a result of dogs ingesting the collar, dogs overdosed because the wrong-size collar was used, or dogs being unusually sensitive. Signs have included tremors and lethargy. The collar has never been documented as a cause of seizures, and certainly not ongoing seizures requiring routine phenobarbital treatment once the collar has been removed.

As far as the “new pill” you say is “not advised for dogs,” we assume you mean Bravecto, Nexgard, or Simparica, all of which protect against fleas and ticks. But according to data amassed by the U.S. Food and Drug Administration and the European Medicines Agency, none of these drugs has any contraindications. They do talk about possible allergies to ingredients, but that’s true for any drug. There’s no reason not to use these medicines in dogs who have seizures. That said, topicals such as Advantix, Effitix, and Vectra 3D are usually preferred by owners, who find it easier than giving drugs by mouth. Any one of these spot-ons will do the trick.

Lluis Ferrer, DVM, PhD, DECVD


  1. I have a 16 year old golden. Two days ago we introduced the Seresto Flea and Tick collar. Last night and now today, we are experiencing seizures???? This has never happened before. Granted, she is 16 in a few weeks but everyone who looks at her doesn’t have any idea just how old she is because she is pretty spry for her age. Coincidence??? Hmmmm

  2. We have a 2/12 year old Cavapoo and a one year old Cavachon. We used the Seresto collar with the Cavapoo with no problem. We also use the collar on the Cavachon and she started have seizures (head cocked sideways and shivering, walking somewhat sideways). We didn’t connect the collar to the condition. One vet suggested starting her on anti-seizure medication, a series of expensive tests, etc. We went for a second opinion and he suggested removing the collar for a period of time to see if anything changes. We removed the collar and within a week the seizures stopped and she hasn’t had any since. We’ve switched to an oral flea/tick medication and all has been fine…..

  3. I have a year and a half year old Lab, Great Pyrenees mix that started having seizures after I put the collar on him. I asked the Vet if they could cause seizures and they didn’t think so and put him on meds. He was fine for a week or two and then I put the collar on him and he had another seizure on the second day of wearing the collar again.

  4. I disagree with this vet and this article. I have multiple epileptic dogs and the “new pills” most definitely cause them to have seizures (bravecto for sure). We have Had to try various medications to see what works best for each of mine which is no easy task. Same with heartworm medications. I do have good luck with Advantix 2 and revolution on one but every dog is different and you have to be careful and find what works for you! My vet gives Valium the day before, day of and day after any of these meds to prevent the seizures. It works MOST of the time! I will be trying the seresto collars this year to see if they can tolerate them- here’s hoping! If not back to the monthly drops. Good luck everyone!

  5. I have a Lab/Pit mix and when we started using Seresto Flea collars about 2 yrs ago he started having seizures and we never connected the collar to his seizures our other 2 had no issues at all for the 2 years of wearing the Seresto during the spring/summer months. Now our boy is on all 3 seizure meds possible..phenobarbital, Keppra, and potassium bromide. Maybe I should bill Seresto for the cost of Aniaml Hospital at $1400. X3 a pop each time and all his meds he is on!!!!! 😔🐾🐾


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