Comfrey, knitbone Symphytum officinale

Comfrey, knitbone

O R I G I N A N D C U LT I VAT I O N Comfrey grows in moist grasslands and on riverbanks in Europe, western Asia, North America, and Australia. Russian comfrey, grown as a fodder crop for cattle, evolved as a hybrid between Symphytum officinale and prickly comfrey (S. asperum)

P L A N T   D E S C R I P T I O N
Comfrey grows to a height of 60–100 cm  (3 ft), and has a thick brown rootstock (rhizome) and mucilaginous roots. The plant is a bristly-haired perennial with large, oval, lanceolate leaves. Its flowers are funnel shaped and white to purple. The parts used in herbal medicine are the rhizome, root, and leaf. 

C U L I N A R Y   A N D   N U T R I T I O N A L   VA L U E
The young leaves have been used as a vegetable, but this practice is discouraged because of the presence of toxic alkaloids (pyrrolizidine).

C L A I M S   A N D   F O L K L O R E
Comfrey has been used in herbal medicine for centuries – it was known to Dioscorides in the first century. The herb has been employed in the treatment of chronic bronchial disease,
gastric and duodenal ulcers, colitis, rheumatism (leaf tea only), and irritable bowel syndrome. Externally, it has been applied to broken bones (hence one of its names), bruises, sprains, fractures, psoriasis, eczema, and other skin conditions.

E V I D E N C E
Of the various chemical substances present in comfrey, allantoin (0.75–2.55%) is said to possess cell-proliferating properties that could assist in tissue healing. Animal studies have indicated that rosmarinic acid
has anti-inflammatory activity. Much attention has been paid to the alkaloids
(pyrrolizidine) (0.3%) in the roots and leaves. These alkaloids are toxic to the liver and, in a number of countries, tablets, capsules, and other products containing comfrey for internal use have been withdrawn from sale. However, comfrey tea seems to be tolerated, possibly because of the
low alkaloid concentration. There is apparently little or no objection to the use of
comfrey in ointments, balms, and other products for the external treatment of the unbroken skin, and as long as the treatment is not prolonged. In Germany, comfrey products are applied externally to bruises and sprains,
but there is a limit to the pyrrolizidine alkaloids contained in the product. Possibly mucilage in comfrey helps
soften the skin.