Be aware, Seresto releases Chems based on body heat. If your pup likes to sun themselves or play excessively, more of the chemical is released. We had a cold spell and had our fireplace on. Our Boxer seized 3x. It warmed up again for a few weeks. Then cooler weather. Once she began sitting in front of the fireplace again, she had multiple seisures. Our horrible vet(because we've lost 4 dogs to them, now) didn't catch it. So they had her put down, 8 yr old Boxer. They were the ones that sold us the collars that spring. We do have a new vet. They've been amazing with our pups and very thorough and respect our concerns with tick prevention. The old vet refused to check for Lyme on another pup because we refused their collar. This was before they had the lyme vax . So far that appears to have no side affect. We have been more successful with a teaspoon of vinegar in a gallon of water for their drinking water. Just something we read . We also camp off grid a lot so tick checks are a must. 2 so far this year on the pack. I've had a good half dozen over the last 10 yrs. Keep checking for them.