I put Hartz flea and tick drops on my male cat Gomer last night. This morning I woke up and he was going crazy. He was shaking and could not stand up. I could tell something was wrong with his nervous system. I called the Vet. He told staight out it was the Hartz flea drops that cause the reaction. He said to wash my cat bring him staight in for an IV. Which I did. I did not even know this website existed until this morning when I was trying to reading up on the subject. So far the Vet has given me a good report. I can pick Gomer up tomorrow morning. But I feel so guilty giving my cat Hartz. I know I am a luck owner. I have read several of this stories that were not as lucky.