I’ve read several stories on this site and I’m sad to say that I know dozens more just like it as I work at an Animal Emergency Clinic. The individuals that say "some animals just have reactions to it like people do to some medications" should really reconsider. If the same amount of people were being affected as the amount of cats we see with Hartz toxicity then there would be millions in damages awards in a class action lawsuit and the medication would have been pulled off the shelf so quick heads would spin. There are simply TOO MANY cats having the same reaction, we see cats in our clinic every other week with it, excessive salivation, muscle tremors, paralysis..our poor vibrating kitties as we call them. Everytime I’m in near pet care products for flea and tick prevention in Walmart I tell everyone I see DON’T USE HARTZ OR SERGEANTS. Spend the extra money for the good stuff Advantage, Advantix (dogs only), and Frontline.