INTERNAL: Precautions must be made in taking this herb internally as there have been cases of pyrrolizidine alkaloid poisoning; however it might not be Symphytum officinale that is the real cause, but Symphytum uplandicum (S. uplanicum)(Russian comfrey). In the United States, both are sold in stores as the same thing so you don't know for sure which one you're getting. Studies have also been done and now the young leaves of Symphytum officinale have been found to contain this alkaloid, however there is also some discussion that S. officinale may contain a substance that cancels out the liver damaging and possibly carcinogenic effects of the alkaloid. Either way, please take care if you take this herb internally and don't take it for more than four months at a time. It is generally suggested that Comfrey (either species) is for EXTERNAL use only. Large doses taken internally for extended (three or more months) may cause HVOD (hepatic veno-occlusive disease (narrowing of blood vessels in the liver thus reducing liver's effectiveness)) and/or liver cancer. It should be noted that Comfrey has never been identified as the cause of any case of liver cancer in humans and only two cases of HVOD have been blamed on Comfrey, despite all the Comfrey that is consumed every day and has been many years. However, it is again best to err on the side of caution. Comfrey/Pepsin tablets, however, carry a much greater risk of causing liver cancer!

EXTERNAL: No known contraindications and is considered to be fairly safe, though due to the speed at which Comfrey heals and closes wounds, care must be taken to keep the wound clean and free from infection while Comfrey does its work. Because of this, Comfrey is not generally recommended for deep or puncture wounds.