I bought Hartz Flea & Tick drops for my cat, Digit. After the first application, he was fine. One month later, I gave him the second application. I went out to run errands for a few hours. when I came home Digit wasn’t at the door to greet me and wouldn’t come running when I called for him. When I found him, he wouldn’t respond to his name, his ears and legs were twitching, he was drooling, and he could barely walk without falling over. I got online and found horror stories about this product. I washed Digit off and took him to the emergency vet. They pretty much told me they couldn’t do anything for him except watch him over night and see what would happen. I decided to take him home. I washed Digit again and within 3 hours he was coming out of the seizures. The next morning he was back to his regular self. Digit and I were lucky.