I used Hartz Control Flea and Tick Replent spray on my cat Merlyn. It was horrible, he started frothing at the mouth, his eyes glazed over and he wouldn’t move. When he did move, he ran like he was trying to get away from it. Luckily he didn’t have convulsions nor did he have to go to the vet. I felt so bad for him though and didn’t realize until just a few days ago that this brand of product was such a problem! I found out on a message board I’m apart of and I give my deepest sympathies to anyone who has lost or almost lost a pet. I am now and forever boycotting Hartz products and will tell anyone who wants to listen my story and anyone else’s story I read.