I have had Percy for thirteen years. I bought the drops for her she is an inside cat but got fleas anyway. After applying the drops she hide ( she has always been shy petted when she wants) the next day she was sick but we had some different food thought that was bothering her. Then we noticed her limping her right paw sore then she started peeing on things and sleeping in her litter box. After talking with our vet we are convinced it has given her demetia as well as disabling her right leg permenantly. some days are better than others but she is currently living in the basement because of the litter box sleeping I will probably have to put her down soon which just sucks because she was in such good health until I used the drops don’t even think of buying the Hartz brand I thank god I figured it out before I used it on the dog too. what a nightmare.