Many fantastic stories are told about this incredible herb, and its common names, bone-knit, boneset, bruisewort, knit bone and the like attest to its healing power. Comfrey, a member of the Borage family, has long been a standard first aid remedy in any herbal medicine chest. Yet, recent research by the Henry Doubleday Foundation that studied the viability of Comfrey as a food crop, has brought Comfrey into the crossfire. It was found that Comfrey (though it is unclear which species of Comfrey was tested) contains certain pyrrolizidine alkaloids, which, it appears, caused rats that had been fed on a diet of Comfrey for 6 months to develop liver cancer. Alarm bells went off everywhere cautioning people to avoid Comfrey and labelling it a dangerous herb. While pyrrolizidine alkaloids do cause cancer of the liver, it should be mentioned that the quantities contained in a normal dose of Comfrey are extremely small. Most herbalists agree that unless vast quantities were consumed on a daily basis it is unlikely that Comfrey would cause any serious damage at all. After all, Comfrey has been used for generations, both internally and externally, without apparent ill effects and many Comfrey fans continue to swear by it, despite the bad press. However, such matters are nowadays in the hands of regulators who don't really know anything about herbs. Still, to be on the cautious side, use the leaves for internal use and roots externally and don't overdo it - as Paracelsus said: Everything is poison; it's the dose that makes the medicine.
Comfrey leaves can be used as a poultice for all manner of bruises, sprains or other damage to the connective tissues, including broken bones and badly healing ulcers and sores as well as for inflammatory swellings. Comfrey leaves are still considered safe for internal use and can be employed to treat stomach ulcers, irritable bowel syndrome and piles, as well as for bronchial afflictions. Comfrey leaves can also be used to treat problems of the mouth: sore, inflamed or bleeding gums and sore throat or hoarseness.
In Medieval times Comfrey was used in sympathetic magic for healing bones. In modern magical herbalism it is recommended for safe travels and also to safeguard one's luggage.