I put Hartz Flea and Tick Prevention on my cat as directed. He began acting lethargic, and I noticed his mouth was very swollen. I had to take him to an emergency vet because it was a weekend. It turned out he’d managed to get his mouth in the Hartz solution while grooming himself and suffered chemical burns all over his lips. He needed antibiotics and pain meds, I’m short a few hundred dollars for the vet bill, but I’m so relieved and happy that he is still alive after reading others’ stories.