although fleas visit pets, and sometimes people, they spend a lot of time in carpets and other furnishings. they also breed in carpets etc. the best defence against fleas in the house is a good hoover. go around everything carefully with this, not forgetting the corners and edges, then go to the vet or supermarket and buy a spray that is designed for household use. do not use this on your cat though. by using frontline you are going to break the egg pupae adult cycle eventually but a good hoover and spray around the house will help a lot.