Bayer Seresto Collar for Dogs Decoded and Debunked

Everyone tells me that I’m an insanely moody person. But you know whose mood is 5x times more unpredictable than mine? The weather of the area I live in. One day, the outside it practically melting and the next minute, it might just start raining. I guess the only creatures who enjoy and benefit from such weather are insects like fleas and ticks.

seresto dog collar reviews

From the beginning of March to almost mid-Nov, my 6-year-old Golden Retriever and 9-year-old Boston Terrier remain covered by fleas and even worse, ticks.

Jim’s (Retriever) skin was the favorite hangout spot of Lone Star ticks, especially. I didn’t know that, I’m no tick expert. That’s what the vet told me while trying to figure out the root cause of his ehrlichiosis, a fancy name for a nasty flu.

Captain (the Terrier) was, on the other hand, like a full course meal for both ticks and fleas. He would always be scratchy, annoyed and down with fever.

My boyfriend, who is a self-confessed dog expert, suggested I try flea bombs, flea and tick shampoos, some anti-parasitic drugs and what not. Unfortunately, none of them seemed to work for more than a month.

I needed something more effective, something longer lasting. Heck! I read about tick paralysis and saw gory pictures of dogs nearly dying from long-lasting flea infestation. I had to opt for whatever option I could find. After some serious Googling, I decided to give Seresto Flea and Tick Collar a try.

Although I was quite skeptical about it, I had no other option at that moment. This review basically documents my experience with this collar. I know there are many dog lovers out there who are just as skeptical as I was. I hope this review helps them to make an informed choice.

Before I dive into the details, let me give you a quick overview of this product.

What is Seresto Flea and Tick Collar?

It is just like any other flea and tick collar with some noticeable differences. It emits a carefully controlled dose of its active ingredients over a period of 8 months to prevent flea and tick infestation.

The reason why this particular product got my attention was its ability to perish these insects in both larvae and adult stages. Technically, this sounds like the most practical way to kill and prevent further infestation.

The Active Ingredients in Seresto Flea and Tick Collar

The two active ingredients in this collar are Imidacloprid and Flumethrin. I’ll be honest with you, my chemistry was never strong and I didn’t know what these two chemicals do. That’s probably what made me more worried. So I did some research and here’s what I found:

Imidacloprid (10%) kills flea and ticks larvae, thus nipping the problem in the bud. But I was more concerned about how exactly it does that. So, basically, Imidacloprid works like a neurotoxin. Instead of chokeslamming the insects, it attacks their central nervous system and paralyzes them.

It can be toxic to mammals as well if the dosage is not carefully regulated. It can pose a moderate threat if ingested orally. But the amount used in this collar doesn’t have the potency to cause any major harm. At least, I haven’t noticed anything alarming so far, so to speak.

A very low dose of Flumethrin (4.5%) in the collar has been used to kill fleas and ticks in the larvae, nymph and adult stages of their life cycle. This particular ingredient gave me hope because according to some studies, this pesticide is nontoxic to mammals. And secondly, it can defuse the toxic effects of Imidacloprid if ingested by your pet.

Working Principle of Seresto Flea and Tick Collar for Dog

Next thing I needed to know was how this stuff actually works. Apparently, these two active ingredients release onto the dog’s fur and then onto skin slowly, over a period of 8 months. This medication takes a while to activate.

From my observation, I can tell you that the flea starts disappearing from the dog’s skin within a day of application. Same goes for the ticks. However, the duration may be longer or shorter depending on the dog breed and the intensity of infestation.

It’s been almost 5.5 months since my dogs are wearing this collar. I’ve to say Captain is a happier doggo now, not a single flea bite noticed during this period. I found 5-6 ticks on Jim’s fur in the 4th month. However, they died a quick death in less than a day. So, yes, I’m happy since my dogs are doing just fine.

Key Features of Seresto Flea and Tick Collar for Dog- Explained!

1. The Active Ingredients

If you are not sure about the chemicals used in a tick and flea collar, read as much as you can about them.

I did my fair share of research and from what I read on several science-y forums, Seresto has been extremely careful about the intensity of dosage. It is powerful enough to kill the insects almost instantly but not so much that your dog ends up with skin issues, bad stomach, and vomiting.

What’s more fascinating is that it actually works on ticks. I can vouch for the fact that not every flea and tick collar is effective on ticks. My dogs owe Flumethrin big time for this.

Now you must be wondering whether it is safe to cuddle with your pets and sleep on the same bed when the collar is on. Well, practically, such little dosage of Imidacloprid and Flumethrin can’t be harmful to fully grown, healthy adults.

My skin is sensitive in the truest sense of the term and I’m unharmed so far, except for the occasional allergic reactions. The reason could be peanuts because even though I’m allergic to them, I sneak in a few spoons every now and then. Whatever the reason is, the allergies have never been severe and got normalized within 2-3 days every time.

But if you have kids in your house, it’s best not to let them sleep with their pets. A kid’s immunity is simply not strong enough and they are generally more sensitive to even mild toxins than adults.

2. Long-lasting Protection

This was the first reason that prompted me to buy this product. I was seriously in desperate need of a long-term solution. It’s been almost 6 months and the collar effect is still going strong. According to the manufacturer, it should last for about 8 months which sounds great.

Now, I seriously don’t know if it will work the same way for your doggo. From what I’ve read, the opinions on the effectiveness of this product are pretty divided.

While there are many happy customers like me, there are users who have reported to observe re-infestation within 2 or 3 months.

To ease your dilemma, I made a list of the dog breeds that reportedly didn’t respond well to this super collar. If your pet falls within this category, you should look for other options. Here goes the list, by the way:

  • Lhasa Apso.
  • Pitbull.
  • Australian Shepherd.
  • Corgi.
  • Labrador.

3. Odorless and Mess-free

I know some flea and tick collars have a strong smell. I carefully “ticked” them out of my list as I knew my doggos would hate them to the guts.

Dogs are extremely sensitive to smell, that’s why this odorless Seresto collar appeared a somewhat safer option to me. However, since it has got two chemicals on the collar, it does leave a tiny amount of residue. But I don’t worry about it much.

It seems like a far better option than those sticky topical creams I applied which acted like a dirt magnet every time the dogs rolled on the backyard ground.

4. Fitting

This collar basically comes in two sizes- one for small dogs and another for large dogs. Now, this is when things get a little tricky. From what I knew, buying a large collar for a small dog isn’t safe at all, as the amount of medication released can be toxic for small dogs.

I bought two large ones as Jim and Captain have large necks, I didn’t face any issue with the fitting. However, if you have a giant beast, even the large one might not be sufficient.

5. Waterproof

I don’t really understand what was the point of making the collar waterproof if it’s going to lose its effectiveness when exposed to water. I open the collars during the bathing time.

And also, while the waterproofing is supposed to safeguard the collar ingredients while swimming or in rain, I still don’t let them swim while wearing the collars. My common sense says that water will easily lessen the potency of the medication.

Side Effects

It’s actually hard to say for sure whether Seresto Flea and Tick Collar is absolutely safe or not. Just because nothing severe happened to my dogs doesn’t mean it’s a godsend.

I have heard and read several reports where people complained about seizures, vomiting, skin rashes, inflammation, hair loss, redness in the eye, fever, allergic reactions, and irritability of their dogs.

There’s one possible explanation of all these. You see, the active ingredients used in this collar are actually pesticides, not drugs.

According to an EPA (Environmental Protection Agency) report published in 2017, 11 types of adverse reactions (on both dogs and their owners) were reported by 14,135 people. However, note that the report documents the fatalities caused by various types of Seresto collars, not just this particular one. You can get a look at the full report here.

However, don’t disregard the credibility of this collar right away just because a lot of people didn’t benefit from this. You have to understand that not all dogs are made equal, just like us humans. Some have extremely sensitive skin, some have low immunity and some react negatively to all types of topical insect repellants.

Another possible reason why some dogs become aggressive, easily irritable after wearing this collar could be that they have never worn any collar before. My pets had cute little, regular collars on since they were puppies. Probably that’s why they didn’t react weirdly when I put on this collar. They were used to this.

Coming to the Less Serious Drawbacks

  • Like Seresto small dog and cat collars, this product doesn’t come with a safety release mechanism. This means if they somehow end up getting stuck to a tree or something, the collar won’t snap and release after a slight tugging by the animal.
  • I really wish the makers made a few more sizes available. If you have a medium dog with a large neck, I have seriously no idea what size to recommend since there are only two.
  • The water-resistance feature is honestly a just a gimmick. But I can let go of this minor design flaw since my dogs are not much of a swimmer. I also don’t let them step outside when it’s raining. You should also make sure to put off the collar before bathing your pet.

So to Sum Up What I Liked and Didn’t Like Much

bayer seresto flea and tick collar for dogsbuy now


  • Starts working within 24-48 hours.
  • Odorless and doesn’t leave much residue.
  • Easy to apply.
  • The medication dosage and slow release system make the collar one of the safest money can buy.
  • Effective for almost 8 months.


  • Not available in multiple sizes.
  • Is not meant for all dog breeds.
  • Isn’t truly waterproof.
  • Exposing the collar to kids for long hours has to be avoided.

Frequently Asked Questions (FAQs)

1. Can Seresto Flea and Tick Collar be used on puppies?

Ans: I won’t recommend it. See, the level of chemicals used as medication in this collar can be toxic for a small puppy. It may cause several side effects.

2. Will it if my dog already has a leash collar on?

Ans: Yes, it will.

3. What is the size of the small caller?

Ans: Dogs from 8-20 pounds should comfortably fit the small collar size.

4. Is Seresto Flea and Tick Collar waterproof?

Ans: Although the manufacturer says so, you will be better off not exposing it to water.

5. How long does it take for Seresto collar to work?

Ans: For fleas- approx. 24 hours and for ticks- approx. 48 hours. This may vary.

The Bottom Line

There you go! The very controversial yet extremely popular Seresto Flea and Tick Collar decoded for you.

Will I recommend it to everyone looking for a safe and effective flea/tick treatment for their dogs? No.

Does it actually work? Yes, but nobody can tell how your dog will react to it. So, I tell you what, before you decide to buy or reject this product straightaway, have a discussion with your vet, maybe show him/her this review. This might truly help you understand whether this is the safest way to go or not. Thanks a lot for reading!


  1. Rich September 6, 2019
  2. Lonnie Olson October 5, 2019
  3. JB July 6, 2020
  4. Melford Burss July 12, 2020

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