My son used the Hartz one spot flea treatment last month and noticed unusual twitching of his kitty’s ears. The second dose came with some scarry side effects! The kitty would climb really high to get away from the ground, along with unusual shaking and fear of my son. We found this website and immediately washed the cat and went to the vet. Much to our surprise, the vet had not heard of these problems with Hartz. I copied off a few pages from this website for him in hopes to warn other innocent animal owners. Fortunately, with fluids, antiobiotics, and a thorough bath from the vet, the kitty is much better now. He doesn’t think there will be any long-term effects. We were lucky. There has got to be something we can do to stop this crap from being on the market!!