I used the Hartz brand flea medicine on our cat & it was not good…he literally spazzed out, kept randomly hissing, walking funny, panting, & distancing himself, very distressed! I had to trap him in the bathroom (normally he wants held & cuddled & loved on) & spray him with our showerhead to get it off. This was within an hour of putting it on! It was awful…we usually use a different brand but was at Walmart & that’s all they had in. Never again!