I just got some. I can let you know eventually how well it works.
For now all I can tell you is that it really cleaned out me AND my two dogs...and my dog really appreciated me powdering her with it after I saw her itching and scratching. The itching stopped almost immediately - like on contact.
So, so far, I'm happy with it on the inside AND the outside.
I need more time to know what else it will do, but they have it really well-priced at the above site.
There is plenty of information if you just google the words "diatomaceous earth".