To get rid of fleas one has to not only treat the animal but the surroundings as well. A flea can live for months without having to feed/bite so they can live in fibers easily, starting the process over when they choose to bite. We use aerosol bombs that we get at Wal-Mart, Ace Hdwe, etc., close up the house and set them off, leave for several hours, return and air out for several more hours - long tedious process and using chemicals that we don't like to use. Washing/cleaning won't get rid of them, at least we've never had success with that. The inexpensive bombs do work. Then the pet has to be treated, hopefully by a responsible vet who won't use harmful ingested chemicals. We used K-9 Advantix once and will never, ever subject any animal to that again. Ours started having neurological problems, then her fur changed and she got mange-y spots, chewed her tail. It took over 6 months to get over one treatment. My brothers dog nearly died from Frontline.
If you check the ingredients and you find one of them is Imidicloprid - it is a chemical that is put on trees to kill the Emerald Ash Borer that is killing millions of ash trees in the midwest!!! We called Bayer and they told us they hadn't had any complaints about K-9 but the message boards say otherwise. Good luck!!