Diatomaceous Earth is very good for getting rid of fleas and other insects such as ants, millipedes, silverfish.I had a flea problem last year. I have cats that go outside and I also have a dirt floor celar. So flea infestation can happen very easily.
So I bought the Diatomaceous Earth put it down around the edges of my floors and in the basement all over and within a week no more fleas.It is a mechanical insect killer and insects don't become immune to it. It dehydrates the insects.
There are some precautions though you have to be careful not to breath it while putting it down or getting it in your eyes.
Some people give food grade Diatomaceous in their pets food and on there skin, but I did not do this.You can buy it at most feed stores and some garden stores.There are lots of places that sell it on the web and will ship it. Diatomaceous earth is made from fossil shells. Try it it really works!