
Have you ever heard of diatomaceous earth (DE)? It is a powder made from the microskeletons of diatoms which live in the ocean. The super-fine powder works by dehydrating the exoskeletons of the flea (or any exoskeleton on any insect), which in turn kills the flea.
DE does not harm your cat or dog, and is effective on all animals, carpeting, & even in the yard as an organic pest control. You can find it in some garden stores, pet supply stores, or online.
Special Note - the DE you find in pool stores is a different grade and should not be used on your pets or in your garden.