Why is the Seresto Collar Not Working?

Reviewed By Julie •  Updated: 11/18/21 •  5 min read
The contents of the OurFitPets.com website, such as text, graphics, images, and other material contained on this site (“Content”) are for informational purposes only. The Content is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. Always seek the advice of your veterinarian with any questions you may have regarding the medical condition of your pet. Never disregard professional advice or delay in seeking it because of something you have read on this website! Some of the links in this post are affiliate links. This means if you click on the link and purchase this item or service, we will receive an affiliate commission at no extra cost to you. All opinions remain our own.

Why is the Seresto Collar Not Working

Online Veterinary 24/7
Chat With A Veterinarian Online

Connect with a verified veterinarian in minutes. Licensed vets are available 24/7 to answer your questions. No need to worry about your furry family member.

Perhaps it sounded funny the first time you heard a collar could prevent and eradicate fleas from your dog or cat. But you made the purchase anyways (anything for your fluffy companion).

Similar to many persons who purchased the seresto collar, you may feel it’s not working. Could you be doing something wrong? First, let’s see why a seresto collar is recommended.


Fleas can be very discomforting to dogs, causing an itching sensation that, when left untreated, can be dangerous to the life of your pet and even affect your home. Detecting fleas is difficult; the 1mm insect hides within the fur. Considering its size, detecting its presence is nothing short of difficult.

Now, the frightening part is how it multiplies on the fur of dogs and cats. It can lay up to 4000 eggs, and worst of all, it sucks the blood of the host continuously.

While the fleas may start around the neck of your pets, they quickly spread to other areas like the tail and head. This answers why your dog may have a loss of hair and bruises in these areas. The strong and persistent itching sensation prompts the use of the sharp canine teeth to relieve the discomforting feeling.

One last thing! Fleas can bite humans, although due to lack of fur, finding a place to stay permanently is quite impossible.

How does a Seresto collar work?

A seresto collar is a common treatment and prevention option for dog and cat owners. The collar starts to work after 24- 48 hours of use and may remain around the neck of the pet for about eight months.

Regardless of how magical a seresto collar may sound, it’s no magic wand. It’s more of a slow and steady process. There are active ingredients of insecticide in the collar, which spreads gradually across the fur. By spreading across to different body parts, the medication repels fleas and ticks alike. Given this, the new infestation of fleas and ticks becomes impossible (your canine friend is safe).

Another way it works is through absorption. Absorption? Yes, you read, right! The seresto collar has ingredients that seep into the fatty layers of the dog or cat. Now, when a tick or flea bites (since they affect dogs and cat the same way), they suck the insecticide and die. In summary, a seresto collar can ward off harmful insects and can as well kill them.

Does seresto collar work?

Yes, a seresto collar works. As mentioned earlier, fleas and ticks stay majorly at the neck. Of course, they may be found on the head and around the tail. Since a seresto collar stays precisely on the neck, it’s one of the most effective methods of ridding a pet of fleas and ticks. Additionally, the head is close to the neck, so the treatment spreads fast to the head. As for the hind parts, the medication will gradually dissipate to ensure that part of the body gets covered and, as such, is well protected against new infestations.

Due to the long-lasting capability of the seresto collar, it keeps working for months. From 7 weeks of age upwards, your dog or cat can use the collar with no side effects. As opposed to other spot-on treatments, the use of a collar is cost-effective and lasts longer. Just one purchase of a seresto collar is needed for months, and the price of most of these collars is usually budget-friendly.

Note: For pregnant dogs and cats, consulting a veterinary doctor before using a seresto collar is vital.

Why is the sereto collar not working?

Aha! Aha! Don’t cut the collar just yet. After reading the information above, you must be wondering why your seresto collar isn’t working after all the outlined capabilities. Could it be that you are doing something wrong? Or perhaps there are things you don’t fully understand about the seresto collar? Read on to see which it is, and see how to make adjustments.

Not 48 hours yet

Slow and steady! A seresto collar takes time to start working. So don’t expect to tie the collar around your dog and immediately wait for fleas and tick to start falling off like dry leaves in winter. It takes up to 48 hours and weeks for it to be fully active. So, patience, please, patience.

Frequent swimming or bathing

Until your fluffy friend is completely free of fleas, reduce the frequency of swims and baths. A seresto collar is water-resistant, but spending too much time in the water will reduce the potency of the medication, which is meant to be present in almost all body parts.

Existing Ticks

Blame it on an advertisement or better still,” lack of adequate explanation.” What you see on most seresto collar packs is “it kills fleas.” However, how it does so is not fully explained. A flea will only die when it bites a dog or cat, which has a seresto collar on for more than 48 hours. And this is because the medication would have seeped into the fatty outer layer of the pet’s skin.

For already existing fleas and ticks, the collar would not affect them except they bite (you would have to remove them with another method).

Faulty or counterfeit collar

There could also be an off chance that you purchased a fake or faulty seresto collar. If you notice increased presence of ticks after using the collar for weeks, then it’s probably just a fake.

When used as a lone treatment

You should try other methods of flea and tick removal, such as the use of spray, oral medication, and spot-on treatments. When this is done, a seresto collar will act more like a repellent, while other methods, especially spraying, will help eradicate existing ticks and fleas.

So, as earlier mentioned, do not neglect your sereto collar. Instead, use other complementary methods to do a thorough cleansing for your pets, and use the collar as a sentinel to keep out a new infestation.

(Visited 759 times, 1 visits today)
Online Veterinary 24/7
Chat With A Veterinarian Online

Connect with a verified veterinarian in minutes. Licensed vets are available 24/7 to answer your questions. No need to worry about your furry family member.


Julie is a graduate of the University of North Carolina, Wilmington, where she studied Animal science. Though contrary to the opinion of her parents she was meant to study pharmacy, but she was in love with animals especially cats. Julie currently works in an animal research institute (NGO) in California and loves spending quality time with her little cat. She has the passion for making research about animals, how they survive, their way of life among others and publishes it. Julie is also happily married with two kids.