about a couple weeks ago i noticed that my dogs pupils were huge. I took him to the vet and his eyes were not responding to light which is the first sign of something wrong in the brain or worse a brain tumor. They put him on penicillian and gave him a cortizone shot in case it may be just an infection in his brain. He asked if I had did anyting different and I mentioned that I had put hartz 3 in 1 on him for fleas. You should have heard the reaction. He said that it can have the same effects has brain tumors and that it actually can mess up the neurological system of your dog along with many other things . Right now we are feeding him popsicles melted in water so that he gets liquids in him and feeding him whatever food he will eat. He has a hard time standing up and walking his back legs just wont support him sometimes. we carry him up and down the steps and walk with him so he can go to the bathroom. Just awhile ago his head just started shaking and it lasted about 3 minutes. not sure if it was a type of seizure or not. We have been sleeping on the floor with him for the past week when it really got bad. I am just praying that it is the hartz and not a brain tumor and that he comes back even half way. it just kills us to see him try and get up and walk and fall over or seeing his head shake. Hartz should be put out of business once and for all. It has killed enough animals and someone has to put a stop to it before anymore die from their products and stupidity.