If anything,I seem to be constantly loosening the one on my dog.Other than not,never had a problem and never had a tick on the dog.There are some fake seresto collars out there.Maybe you picked one of those up.
Your best to buy them from your veterinarian. There are a lot of fakes out there. See a cheap one on amazon, Good chance its fake. Two months ago a friend was complaining he found engorged tics on his dogs and that he had just put new Seresto's on them two weeks before. I asked where he purchased them at. His wife got a killer deal on Amazon. My wife's a vet tech and she checked them out . They where fake.
This time around, they don't wanna stay on. These ones either came from Walmart or the vet. You'd think for that kinda money, they could devise a system to keep the collar ON the dog. When they stay on, they seem to work pretty well.
Before we used the Serasto collars we had our sheltie vaccinated for lime disease. Later we took her for her yearly shots and I notice she had two ticks on her ear. She tested positive and the vet. gave her an antibiotic shot and we started using the Serasto collars.
The next trip to the vet. she tested negative. Since we have been using the collar we check and brush her regularly and we have found no ticks on her probably four years now. Better than I can say for myself. She plays and lays in the 2 acre grass back yard daily and goes for walks in the woods.
The Serasto collars do have a recommenced time of efficiently of 8 months and may not perform best for a short time after a bath.
The vet. has a map in his office with flags denoting the location of dog residence where lime disease was been confirmed with testing and around our residence it is very high.
Also I have learned over the last few years one can contact ticks any month of the years in PA.
I have one on my 5 yr old - no problems works great been using it since she was a pup. The younger one seemed to have an adverse skin reaction to it ... horrible rash down her chest - she scratched her chest raw with the scratching. Since the collar was the newest thing that changed (previously she was on the oral, but I liked the serasto so well on the older dog - i wanted it on her as well) ... we took the collar off of her and after a few days of hydrocortozone cream the rash and itching cleared up. I do notice that if she spends alot of time wrestling or playing with either my older dog or my buddy's dog (who both wear the collars) that she'll start to get a rash again. But will go away fairly quickly afterwards if she's not playing or laying on top of them.
My wife found "a deal" on line as well. They ended up being shipped from South Africa ... She then was worried about the fakes & called Bayer. All Bayer could tell her that what she had wasn't from the US and they suggested calling Bayer South Africa to see if they were real or fake (the packaging was slightly different) They also told her that since they were made for overseas use Bayer USA couldn't even tell her if the formula was the same as what was manufactured in South Africa and really they shouldn't even be shipped into the country that way. Lesson learned - both were returned to the on-line merchant & we actually did get a refund for them.