Great question! At Herbsmith we use Food Grade Diatomaceous earth which is considered safe to consume. Food grade DE is uncalcined and less than 2% crystalline silica.
The science behind using it for its ability to remove giardia from the stool. Many dogs have low-grade chronic presence of giardia in their colons leading to soft stool or recurrent mild bouts of diarrhea. Chronic soft stool is the most common causative factor in impacted anal sacs and scooting (the poor attempt to manually express the irritated, full anal sacs).