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Comfrey: Symphytum Officinale, Gum Plant, Knit Bone, Nipbone

Botany: 

Comfrey has white, purple, or pink flowers with five petals that are ½ to ¾ in. long.  The  stems and leaves are hairy and grow to a height of 3ft.  It can grow in Zone 5 and requires rich, moist soil with a pH of 6.5-7.5. Comfrey grows best in full sun though it is tolerant of shade.  Seeds should be planted in the fall or spring, although planting and transplanting roots is more reliable than seeding.  When transplanting comfrey, be sure to remove all roots or the plant will grow again.  Dead leaves should be removed in the fall.  Leaves for a liquid fertilizer can be harvested from early summer to fall, and leaves for medicinal use should be harvested during blooming due to lower alkaloid content.

Chemistry: 

Medicinal properties come from allantoin, tannin, mucilage, and rosmarinic acid.  However, the chemicals are noually distributed within the plant.  The roots contain 0.6-0.7% allantoin and 4-6.5% tannin while the leaves contain 1.3% allantoin and 8-9% tannin.  Allantoin is an astringent, keratolytic, and promotes cell growth making it useful in healing wounds and ulcers.  Tannin is an astringent that affects the mucous membranes of the respiratory tract including the mouth and throat.  Rosmarinic acid inhibits microvascular pulmonary injury and acts as an anti-inflammatory.  Mucilage is a demulcent.

While comfrey has been a traditional medicinal herb, its safety has recently been called into question.  It was been shown to contain pyrrolizidine alkaloids which are toxic.  Specifically, echimidine, symphytine, and lasiocarpine have been found with the latter two shown to be carcinogenic in rats.  The root of the plant contains one hundred times the amount of alkaloids as the part of the plant above ground.  However, the chemicals are not equally distributed within the plant.  The roots contain 0.6-0.7% allantoin and 4-6.5% tannin while the leaves contain 1.3% allantoin and 8-9% tannin.

Fun Fact:

 At one time comfrey was used to “restore” a woman’s virginity. She would take a bath in comfrey which would repair the hymen.

History: 

Comfrey was introduced to England during the Crusades, and it spread to America during the 1600’s.  Native Americans used comfrey to treat bloody discharge from the oral, anal, or urinary orifices.  Traditionally, comfrey was used to create a plaster to set and cure broken bones giving it the name knit bone. Comfrey has also been used in racehorse feed, as a liquid fertilizer, and to treat animal wounds.

Uses/Pharmacology: 

The roots and leaves of comfrey are used medicinally.  Traditionally, comfrey was used to create a plaster to set and cure broken bones giving it the name knit bone.  Externally, the plant is used as a poultice to reduce swelling around bones, treat cuts and burns, and a compress can be made to treat varicose veins.  Until recently, comfrey has been used to treat a wide variety of problems internally (including arthritis, asthma, and anemia) though mostly used as a tonic or tea to treat ulcers.  Native Americans used comfrey to treat bloody discharge from the oral, anal, or urinary orifices.  Less common uses focus on the digestive tract including gallstones, dysentery, diarrhea, and certain types of cancer.

Dosing/Recipes:  

Alma Hutchens suggests equal parts comfrey and elecampane to make a demulcent.  A tea can be made by boiling one teaspoon of fresh or powdered comfrey in one cup of boiling water and steeped for half an hour.  The tea is to be taken four times a day totally one cup a day.  When used as a tincture, a treatment 5-20 drops should be used four times daily and a poultice can be made using fresh or dried leaves or a powder.

Contraindications/Interactions/ Adverse Reactions: 

While comfrey has been a traditional medicinal herb, its safety has recently been called into question.  It was been shown to contain pyrrolizidine alkaloids which are toxic.  Specifically, echimidine, symphytine, and lasiocarpine have been found with the latter two shown to be carcinogenic in rats.  The root of the plant contains one hundred times the amount of alkaloids as the part of the plant above ground.  There have been cases of human poisoning when ingesting large amounts of comfrey resulting in death of liver failure, and ingestion of comfrey is no longer recommended.  As a result, comfrey should not be used when nursing or pregnant.  External use has been debated with some sources stating that comfrey can be used externally with specific limitations while other sources say the risks outweigh the benefits stating that other treatments can have the similar results without the risks.

References Cited:

 1.Foster S, Duke JA. Peterson field guides: eastern/central medicinal plants and herbs. 2nd ed. New York: Houghton Mifflin Company; 2000. p.204-05.

2.DerMarderosion A, Beutler JA, editors. The review of natural products. 4th ed. St.Louis: Wolters Klumer Health, Inc; 2005. p.311-14.

3.Hutchens AR. Indian herbology of North America. Boston: Shambhala Publications, Inc.; 1973. p. 92-94.

4.McVicar J. Herbs for the home: a definitive sourcebook to growing and using herbs.New York: Penguin Group; 1995. p. 188-89.

5.Newcomb L. Newcomb’s wildflower guide. New York: Little, Brown and Company; 1977. p. 188

6.Ody P. The complete medicinal herbal. New York: DK Publishing, Inc.; 1993.

7.Powell E. From seed to bloom: how to grow over 500 annuals, perennials & herbs. Pownal: Storey Books; 1995. p. 264.

8.Skidmore-Roth L. Mosby’s handbook for herbs & natural supplements. 3rd ed. St. Louis: Elsevier Mosby; 2006. p. 336-39 

9.Sweetman SC, editor. Martindale: the complete drug reference. 35th ed. Grayslake: Pharmaceutical Press; 2007. p. 1431, 2170.

10.Tyler VE. Herbs of Choice: the therapeutic use of phytomedicinals. New York: The Haworth Press, Inc.; 1994. p. 158-60.

11.Tyler VE. The new honest herbal: a sensible guide to herbs and related remedies. 2nd ed. Philadelphia: George F. Stickley Company; 1987. p. 76-78.

Researched By: Ray Holmes