Hi Holly,
really sorry to hear this occurred. To me, this could certainly be an adverse reaction to the collar itself. The only other possibility is that I have seen cats who are not accustomed to wearing collars scratching themselves repeatedly to the point of causing a good deal of irritation and even bleeding, simply because they don’t like the collar.
But if your cat was used to wearing collars and this occurred all on its own with no signs of self mutilation, I would make sure to report this to the manufacturer of Seresto, which is Elanco.

Hi Logan,
Because you’re seeing hair loss in multiple places and not just where the collar is, it’s not a bad idea to connect with your vet just in case there could be another cause that might be apparent to them by having a look at your cat. If the collar is the likely underlying cause and if you’ve had a good experience with Seresto collars for some time and the issue is only occurring with a newly purchased collar, I would first make sure the product you purchased is authentic. There are some very convincing looking fake products on the market. If you are certain it is genuine, I would consider contacting the manufacturer (Elanco) to report this issue. It may be helpful for them to trace the lot number and see if there are any similar concerns that have been raised by other customers. Here is the link for their contact page. I would try the number at the bottom to speak with one of their veterinary professionals: https://yourpetandyou.elanco.com/us/contact-us

Hi Cesar,
Thank you for sharing your experience. It’s always helpful to keep in mind that as individuals, any animal could have a adverse response to a new medication even if other pets in the home have not. Hopefully you are able to find another product that will meet your kitty’s needs.

Hi Laura,
There is no specific minimum weight stipulation provided by Elanco, only that the kitten must be at least 10 weeks old. At a minimum you’d want to wait at least another week before using one. If your kitten is around 3lb at 10 weeks, that is at the upper end of the weight range for that age. Waiting until your kitten is 3lb should be well within the expected safe weight range.

Hi Dianna,

The Seresto collar is largely only effective against adult fleas. Flea larvae are minimally affected and flea eggs are not. The collar can kill adult fleas before they are able to lay eggs, but if there was a pause or lapse in use of a collar, allowing any eggs or larvae to be introduced by adults before they were killed, the collar will not be able to eliminate those younger stages of the infestation. Now, it’s true that eventually any eggs and/or larvae on a cat and in the environment will develop into adults and the collar will kill them, but this may take some time depending on how many eggs or larvae we’re talking about. An adult flea can lay 50 eggs a day.

Fake/counterfeit Seresto collars have also been documented. Hopefully this wouldn’t be an issue at Tractor Supply, but is worth mentioning.

A research paper from 2020 looking at different flea/tick products for cats did not find any evidence thus far for developing resistance to imidacloprid, the active ingredient for fleas in the Seresto collars.

It is more common for a perceived product failure to be related either to incorrect use of a product or incorrect expectations. But if a product failure is truly suspected, contacting the manufacturer (Merial) may be helpful.

Currently, you may consider using a product that can kill eggs and larvae more effectively. Advantage II for cats and Frontline GOLD would be examples.