I bought HARTZ advanced care flea and tick drops for cats and kittens waying under 10 pounds. This stuff is horrible. It smells like fabric softener sheets and it gave my cat smelly spiked hair on the back of its head. I put it on my little cat and by bigger one who is probably over 10 pounds (oh well) as a preventitive measure as it says it lasts up to a month. I hope this stuff comes off soon, the cats hate it! I had to wash it off of the little kitten, and the big one doesnt seem too happy about it! I’m glad they werent allergic, but I just put it on yesterday and I hope nothing happens. Best of luck! Ban Hartz!