Comfrey (Symphytum officinale ), or common comfrey, has been known by many names, including boneset , knitbone, bruisewort, black wort, salsify, ass ear, wall wort, slippery root, gum plant, healing herb, consound, or knit back. This distinctive herb, considered by the English herbalist Culpeper to be "under the dominion of the moon," is a member of the Boraginaceae family. The genus name Symphytum is from the Greek word sympho meaning to unite. The common name comfrey is from the Latin confirmare meaning to join together. The herb is named after its traditional folk use in compress and poultice preparations to speed the healing of fractures , broken bones, bruises , and burns . comfrey is a perennial native of Europe and Asia and has been naturalized throughout North America. There are about 25 species of the herb, including prickly comfrey (S. asperum ) and Russian comfrey (S. X uplandicum, known as okopnik). In Russian medicine, the herb is considered poisonous when used excessively.
Comfrey grows well in rich, moist, low meadows, or along ponds and river banks, where it may reach a height of 4 ft (1.2 m). Comfrey root is large, branching, and black on the outside with a creamy white interior containing a slimy mucilage. Hollow, erect stems, also containing mucilage, are covered with bristly hairs that cause itching when in contact with the skin. The thick, somewhat succulent, veined leaves are covered with rough hairs. They are alternate and lance shaped, with lower leaves as large as 10 in (25 cm) in length, and dark green on top and light green on the underside. Small, bell-shaped flowers grow from the axils of the smaller, upper leaves on red stalks. Flowers are mauve to violet and form in dense, hanging clusters, blooming in summer. The cup-like fruits each contain four small, black seeds.
Comfrey root and other parts of the herb have been valued medicinally for more than 2,000 years. The specific name officinale designates its inclusion in early lists of official medicinal herbs. Comfrey has been prepared as a poultice or compress with healing properties for blunt injuries, fractures, swollen bruises, boils , carbuncles, varicose ulcers, and burns. The external application of comfrey preparations may minimize the formation of scar tissue. Poultices were also applied to ease breast pain in breast-feeding women. Comfrey, taken internally as a tea or expressed juice, has been used to soothe ulcers, hernias, colitis, and to stop internal bleeding. As a gargle it has been used to treat mouth sores and bleeding gums. The herbal tea has also been used to treat nasal congestion and inflammation, diarrhea , and to quiet coughing. The hot, pulped root, applied externally, was used to treat bronchitis, pleurisy , and to reduce pain and inflammation of sprains.
The herb is thought to loosen congestion, soothe irritated membranes and skin, reduce bleeding, tighten tissues, and heal wounds . The allantoin in comfrey, found most abundantly in the flowering tops, has been identified as the source of much of the herb's healing actions. Comfrey, applied externally to superficial wounds, promotes the healing of connective tissue, bones, and cartilage. Other constituents found in comfrey include tannins, resin, essential oil, gum, carotene, rosmarinic acid, choline, glycosides, sugars, betea-sitosterol, and steroidal saponins.
Comfrey contains vitamins A and B12, and is high in calcium, potassium , and phosphorus . The herb has long been used as a cooked green vegetable in early spring, and the fresh, young leaves have been added to salads. The widespread suffering caused by the Irish potato famine of the 1840s motivated Henry Doubleday, an Englishman, to fund research into comfrey's potential as a nutritional food crop. Farmers have valued comfrey as a nutritious fodder for cattle. When the leaves are soaked in rainwater for a few weeks, they will produce a valuable fertilizer for the garden, especially beneficial to tomatoes and potatoes.
Modern herbalists, however, disagree strongly about comfrey's safety, particularly when herbal preparations are taken internally. A Japanese study in 1968 implicated comfrey constituents (known as pyrrolizidine alkaloids) as being toxic to the liver even when taken in small amounts. The study involved large amounts of comfrey extract rather than the whole herb. The most toxic of these pyrrolizidine alkaloids, according to Varro Tyler of the Purdue University School of Pharmacy, is echimidine. This alkaloid is found primarily in Russian comfrey and prickly comfrey rather than the common comfrey. However, Tyler cautions that other alkaloids toxic to the liver are present in common comfrey, and commercial preparations may not distinguish between the types of comfrey contained in the products offered for sale. Herbal products containing echimidine are prohibited for sale in Canada as medicines. In fact, all comfrey products made from the root, which contains a higher concentration of pyrrolizidine alkaloids, are restricted in Canada.
A 1978 Australian study reported that rats fed a large diet of comfrey leaf developed liver cancer . The research literature has reported some cases of liver toxicity attributed to long-term, internal use of comfrey. However, some Japanese doctors still continue to recommend a vinegar extract of comfrey to treat cases of cirrhosis of the liver, despite these previous research findings of the hazards associated with internal use. The research on the safety and effectiveness of comfrey as a medicine continues with some conflicting research results. In Germany, where standardized comfrey remedies are commercially available, the allowed dosage and duration of treatment is regulated. In the United States, however, commercial preparations may not be standardized to meet these dosage restrictions.
Ointments, salves, and oil extracts of comfrey are available for external treatment. The crushed or powdered root and extracted juice of the herb are used to make poultices for external applications. Comfrey extract is an ingredient in commercially prepared medicines for chest congestion, coughs, and pain relief.
Comfrey should not be used, either externally or internally, by pregnant or breast-feeding women. Many herbalists caution against internal use of comfrey. This caution is due to the dangers of the pyrrolizidine alkaloids that are toxic to the liver and may have cancer-causing effects, even in small amounts. Consumers should avoid external use of comfrey on deep wounds because the herb may promote premature healing of surface tissue before the deeper damage has been healed. Wounds must be thoroughly cleaned before application of comfrey remedies to avoid tissue forming over dirt particles. Comfrey preparations should not be used for more than four weeks. Gathering comfrey in the wild may be dangerous for the novice herbalist because the early spring leaves somewhat resemble the deadly ones of nightshade and, in some reported cases, ingesting comfrey in preparations contaminated with deadly night-shade has led to poisoning.
No side effects are known with proper preparation and administration of Symphytum officinale in external, therapeutic applications. Internal use of herbal preparations should be avoided pending further research.
Hutchens, Alma R. A Handbook of Native American Herbs.
Boston: Shambhala Publications, Inc., 1992.
Ody, Penelope. The Complete Medicinal Herbal. New York: Dorling Kindersley, 1993.
PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company, 1998.
Polunin, Miriam, and Christopher Robbins. The Natural Pharmacy. New York: Macmillan Publishing Company, 1992.
Tyler, Varro E., Ph.D. The Honest Herbal. New York: Pharmaceutical Products Press, 1993.
com·frey / ˈkəmfrē/ • n. (pl. -eys) a Eurasian plant (genus Symphytum) of the borage family, with large hairy leaves and clusters of purplish or white bell-shaped flowers. See also boneset.