DE is Diatomaceous Earth (sp?)...it is a natural mineral powder which is very effective in controlling external and internal parasites. You want to get the the Food Grade kind, if you get it. Lots of people like it because there is no chemicals in it. I think our birds don't like it because it is white and they are suspicious of the color, but we will probably get some to mix in the dusting holes in the barn over the winter, we mix it with the dust already there. Cheapest place to get it that I've found is www.hoeggergoatsupply.com