Comfrey

Encyclopedia of Alternative Medicine, Apr 06, 2001 by Clare Hanrahan

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. × 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.