How long after a flea bite would you still itch?

My sister recently found fleas in her house, previous to this her and her baby and my self included had been itching on and off for a couple weeks after many doctors appointments and anti itch treatments she found the fleas she it not staying at her house until we have set off bombs and sprayed down the house. everyone is still itching and have not been in the house for 2 days this is really irritating. so my question is how long will this continue or is this possibly something else we are pretty lost and have talked to doctor after doctor and no one seems to have the answer