My parents used these drops on all of our pets, and my cat Tigger started getting sick about a week after each application. At first we didnt know what it was, we didnt connect the dots. He would lay around all day, wouldnt eat or drink. After the first trip the vet said it looked like he got into something he shouldnt have, so we locked up everything we could think of that he could have gotten into. The second trip to the vet she said he might have gotten into something outside. By the third trip we had connected the dots and we asked the vet about the drops without mentioning that we used them. She said that they are very poisionous to cats and dogs and that she suggests that we dont use them. Well we live in the woods and if we didnt use something the ticks would eat our animals alive. We told her that everytime we used them he got sick. She said to try frontline because it isnt as bad for them. We have switched and havent had problems since. I was wondering if anyone else had similar problems.