My husband put this Hartz ultraguard plus drops for cats on our kitten. He was 16 weeks old which was old enough. A week later, he could not move. He lost all control of his nervous system. We took him to the vet and the receptionist immediately knew that it was Hartz flea drops. We took him into the vet and he said that same thing. He had to give him an injection of a sediative and an antibiotic. After about a day and a half, he could move again. These drops will kill your pet!!! Do not use it!!!