Although I have used Hartz on my cat before with no issue, it was different this time. Last night I put the Hartz flea drops on both of my cats. Almost immediatly they began licking it off and acting crazy. My boy cat was fine after awhile, but my girl cat become sick and lethargic. Luckily she is feeling better today, but I am definatley not using that brand again. One thin I was wondering is, it says not to get in cats eyes or mouth on the package…bt I dont know how you can really stop a cat from licking itself. Why hasnt anyone came out any non-toxic flea drops???