Program is the safest long lasting flea treatment for pets-- I used to work in a veterinary hospital and I have seen many cats have serious reactions to  Advantage and Frontline, which are topical pesticides. Read the inserts for Advantage and Frontline, it says that they are NOT safe for sick animals, young kittens, etc, etc. My cat is allergic to both Frontline and Advantage. Frontline gave him a lump in his neck and Advantage gave him a bald spot where I applied it, and he kept trying to lick the spot.