I put a Hartz flea and tick collar on my dog over the weekend. He woke up this morning with all 4 legs moving so fast he couldnt stand, he finally started to walk and was falling into walls, falling flat in the floor. He couldnt see, he didnt seem to know who I was. I have never seen anything like it. I immediately thought he was having a reaction to the collar and removed it. After what seemed like forever, he began to calm down and came to me exhausted, but he still didnt seem to be able to see. He is now laying on the couch sleeping like he is exhausted, but he seems to be ok . That is when I started looking online to see if it could have been the collar, and found your website. I wish I would have thought to explore the subject before using the collars , but Hartz has been around forever , you think it would be a safe product !!!! Has anyone else had a dog have this reaction, and if so was it only once or is this going to be a permanent thing ?