Comfrey has gotten a bad rap about damaging the liver.
People who use bloodroot extrernally should be very cautious with the products that contain very much zinc. It will eat a very large hole in your skin if you do not use very small amounts! Trust me - I KNOW!
I like it internally in the Dru Browning Herbal Prostate Cancer Tonic and the Jon Barron Blood Support product that uses many of the same ingredients as the Browning formula.