daitomaceous earth is not toxic in any way for human consumption as long as you buy food grade and not filter grade. It is composed of silica which we all need. It kills bugs because of the shape of the diatom in that it cuts the bugs outter shell and dehydrates them. Thousands of people take it with nothing but positive changes. the pharmaceutical companies cannot patent it so you don't hear much about it except by word of mouth.
I agree with Pax and would suggest the antiparasitic herbs....they work great!
You have to buy food grade. The stuff is mainly used as an insecticide, especially for ants, fleas, ticks, bed bugs and such. Internally, it's for parasites such as worms. It is obviously toxic, as is anything that kills any living organism. There are alternatives, such as anti-parasitic compounds that will usually contain black walnut hulls, wormwood, and other anti-parasitic herbs. If you do try the earth, don't inhale it or get it in your eyes, and learn how to use it as safely as possible first. And remember, use food grade. Don't buy it at your garden center!