Latin name: Symphytum officinale
Part Used: Leaves, roots
Use: The impressive wound-healing properties of comfrey are due at least in part to the presence of allantoin. This chemical stimulates cell proliferation and thus supports wound healing. Used externally, comfrey leaf speeds wound healing and fosters proper scar formation. Care should be taken with very deep wounds, however, as external application of comfrey can cause tissue to form over the wound before it is healed deeper down, which can lead to abscess. Used as a compress or poultice, the herb may be used to treat external ulcers including chronic varicose ulcers, wounds and fractures. It has a reputed anticancer action in European folk herbalism.
Actions: Vulnerary, demulcent, anti-inflammatory, astringent, expectorant.
Constituents: Allantoin; pyrrolizidine alkaloids, including echimidine, symphytine, lycopsamine, symlandine (found in fresh young leaves and in the root but not in the dried herb); phenolic acids (rosmarinic, chlorogenic, caffeic and lithospermic); mucilage (about 29%), composed of a polysaccharide containing glucose and fructose; miscellaneous: choline, asparagine, volatile oil, tannins, steroidal spanning, triterpenes.
Safety Considerations: Long-term studies with rats have demonstrated the the pyrrolizidine alkaloids (PAs) in comfrey are hepatotoxic, carcinogenic, and mutagenic. This herb must therefore be recognized as a potentially genotoxic carcinogen with a low risk of genetic damage from PAs. An average cup of fresh comfrey leaf tea may contain up to 8.3 mg alkaloid. To minimize potential risk, lengthy internal use is discouraged. Applied externally, comfrey poses no risk of toxicity.
You can find comfrey in Forage & Soothe's Comfrey Ointment.
Sources:
Hoffman, D. Medical Herbalism: The Science and Practice of Herbal Medicine. Rochester, Vermont, Healing Arts Press, 2003.