When we had a flea problem we went to the vet and he gave us a whole system - a spray for the dogs (he didn't like the oral medications at the time - his opinion was if it kills the fleas it can't be good for the dogs, but there are new ones since then), a spray for the house that killed eggs, larvae, and whatever else fleas have, and a spray for our backyard. He said if we didn't treat all those areas the fleas would just come back. We got fleas when we took in a stray and he had them so bad we could see the things jumping on the floor where he had just been laying. Anyway, after we treated all three places we didn't have any problems anymore. I don't remember what the stuff was called but I'm sure asking the vet for advice would work.