i dont use hartz at all. if i have a kitten thats under the age of treatment i give them a bath in the blue Dawn dish soap let it sit for a few minutes rinse and brush them out with a flea comb. repeat few days later. when they reach the age for treatment i use advantage multi from my vet. hartz is garbage. theres a reason their product is so much cheaper then the other brands. i will never ever buy a hartz product, ever. spread the word hartz is garbage.