My baby was very lucky. She did not become ill but about 10 days after using Hartz, her fur started coming off, skin and all. It came off in patchs around the neck about the size of 50 cent pieces. She had been in my basement and I couldn’t think of anything she could have done to hurt herself but it looked like she had been cut with something sharp. I had no idea that it was from Hartz. I took her straight to the vet and that is when I found out what it was. I no longer use Hartz or any of the over the counter flea preventions. Like I said, we were very lucky that she didn’t get sick. I was shocked when my vet told me that they saw a lot of cats and they weren’t so lucky.