I used Hartz flea treatments on both of my cats one night before bed. One of the cats licked all the treatment off during the night and when I woke up she was trembling, very weak, and her eyes were dialated – the other was fine. I took them both to my vet. $300 and a day at the vet later she was fine. I wrote to Hartz as they instructed and they reimbursed me for the full bill amount plus the cost of the flea treatment.