I use Paradyne topical monthly for heartworm. Stopped using any flea/tick/mosquito about two years ago. I just do not like putting further chemicals on my boy. And, now that he's older (eight), he's not venturing into the woods like he used to and any tick that may happen to get on him is easy to see and remove (being he's a red/white boy). I do wonder at times though about not protecting against fleas.....?