I have two five-month old cats. I used the One Spot Treatment on both of them and while the other was fine one became immediately ill. He was listless as others described and began throwing up huge amounts of puke for his size. I gave him a bath to wash off the goo and instead of licking himself clean he just sat motionless on a chair. I brought him to the vet and the vet essentially said that, ‘some cats are sensitive to this brand of flea treatment.’ My vet did not charge for the visit and gave Max a good once over to make sure he was truly fine.
There is nothing more to say that others have not- I will NEVER recommend this product to anyone and absolutely heed ‘buyer beware’ for all Hartz products.
I should have known from the picture of the cat on the package- he doesn’t look very happy either!