I used Hartz topical flea medicine for my cat and minutes after applying it her hair fell out in clumps. I noticed her skin was very irritated where I applied it. It has been 6 days since I applied the medicine and her fur is still falling out. On top of that SHE STILL HAS FLEAS, it did not kill any fleas what so ever. I am throwing the rest of this flea medicine in the trash. Very scary to see how badly my cat reacted to this. I have never seen her have a bad reaction to other flea meds. Stay away from Hartz.