Comfrey

Location

Comfrey is a perennial herb of the Boraginaceae family.  Native to the continent of Europe, numerous species are now cultivated throughout the world (Stickel and Seitz 2000).  Typically, comfrey species are found growing in disturbed sites, especially moist areas (Culpeper 1814).

Description

Comfrey typically has long, thick, dark roots, and hair-like lanceolate leaves that grow in an alternating pattern along the stem.  Depending on the species, comfrey plants can grow anywhere from 5 to 150 centimeters in height. They possess small, bell-shaped flowers that are colored in shades of purple, white, or pink and contain small black seeds.  The plant usually flowers in June or July and sheds its seeds in August (Fugh-Berman 2003; Culpeper 1814). Common comfrey (S. officinale), prickly comfrey (S. asperum) and Russian comfrey (S. xuplandicum) are some of the more commonly used species.

History

Symphytum spp. has a long tradition of use for treating various ailments via both external application and ingestion.  Believed to have both anti-inflammatory and analgesic properties, various parts of the herb have been applied topically in preparations of creams, oils, demulcents, poultices, mucilages, or the like to speed healing and to relieve pain and swelling.  These blends serve as treatments for joint pains, sprains/distortions, fractures, hematomas, thrombophlebitis, wounds, cuts, hemorrhoids and other conditions including breast tenderness in nursing women (Stickel and Seitz 2000; Culpeper 1814; Mills and Bone 2000).  Though there are some medieval texts that offered words of caution against ingesting comfrey preparations, it was generally considered safe for treating internal ailments including indigestion, ulcers, gastrointestinal cramping or bleeds, respiratory congestion, diarrhea, and rheumatic complaints (von Hildegard 133). Oral preparations included decoctions and syrups (Culpeper 1814; Mills and Bone 2000).  Comfrey has also been consumed as a cooked green, though its culinary use was far less common than its medicinal utilization. 

Current medicinal and culinary uses

Symphytum species contain mucilage, tannins, saponins, and allantoin. Comfrey also contains unsaturated pyrrolizidine alkaloids (PAs) that are toxic (Evans 1998).  The discovery and identification of pyrrolizidine alkaloids (PAs) in comfrey led to changes in recommendations for its preparations and use both medicinally and in foods.  Medicinally, comfrey is still popular for topical treatment of wounds, burns, contusions, sprains, minor cuts or scrapes, swelling, and osteoarthritis.  Allantoin compounds, responsible for the healing effects of comfrey, have been shown to stimulate cellular turnover and tissue regeneration (Fugh-Berman 2000; Foster 1999; Stickel and Seitz).  Comfrey roots contain a greater percent of allantoin than comfrey leaves (Foster 1999).  Randomized placebo-controlled trials have shown it to have both statistically and clinically significant effects on reducing pain and swelling and improving mobility in cases where it may have been impaired (Grube 2007; Koll 2004; Barna 2007; Kucera 2004 & 2005).  One study demonstrated that it may be more effective than over-the-counter topical NSAID creams for treating Oosteoarthritis (D’Anchise 2007).  

Comfrey leaves are sometimes used in teas, salads, cooked as vegetables or added to soups.  In some instances, roasted comfrey roots have been used as a substitute for coffee (Fugh-Berman 2000).  Comfrey roots have ten times the concentration of PAs found in the leaves (Foster 1999); however, adverse reactions have resulted from ingestion of comfrey leaves, too.  The plant alkaloids are highly water-soluble; boiling or steaming the leaves in several changes of water may reduce toxicity.

Even though some compounds in comfrey stimulate healing of damaged tissues and reduce inflammation, the benefits that oral ingestion may have for bronchitis, ulcers, diarrhea, or inflammatory GI conditions are generally outweighed by the risk of liver damage due to the toxic PAs naturally occurring in the herb (Mills and Bone 2000).  Comfrey is harmless when used topically and should not be consumed orally.

Adverse effects

Ingestion of comfrey has resulted in many serious adverse effects including at least two deaths.  A 23-year-old man died from liver disease after consuming comfrey leaves (Yeong 1990).  In addition, an unpublished case was reported to USP Practitioners Reporting Network of a fatality resulting from liver damage in a man who drank comfrey tea.  Veno-occlusive disease was observed in a 49-year old woman after ingestion of an unknown species of comfrey tea (made from root powder) and comfrey-pepsin pills consumed over a four month period (Ridker et al. 1985).  Similarly, a case report of veno-occlusive disease resulted in a 13 year old boy given comfrey leaf tea over a 2 to 3 year period as a treatment for inflammatory bowel disease (Weston et al. 1987).  These and numerous other studies have shown unsaturated PAs to be hepatotoxic—leading to cases of veno-occlusive disease, liver failure, and even death. Unsaturated PAs are also associated with  carcinogenesis or mutagenesis (Evans 1998).  Pyrrolizidine alkaloids are poorly absorbed through the skin, unless broken, so topical use of comfrey is considered benign (Fugh-Berman 2000, 93). Although topical use of comfrey was well tolerated in many studies, a few cases of skin irritation occurred (Koll 2004; Mills and Bone 2000).

References

Barna, M.; Kucera, A.; Hladicova, M.; Kucera, M. "Wound healing effects of a Symphytum herb extract cream (Symphytum x uplandicum NYMAN): results of a randomlized controlled double-blind study." Wien Med Woschenschr. 2007; 157: 569-74 . 

Culpeper N. Complete herbal. London: Richard Evans; 1814.

D’Anchise R, Bulitta M, Giannetti B. "Comfrey extract ointment in comparison to diclofenac gel in the treatment of acute unilateral ankle sprains (distortions)."Arzneimittelforschung. 2007; 57(11): 712-6. 

Evans WC. Trease and evans' pharmacognosy. 14th ed. Philadelphia: Saunders; 1998.

Foster, Steven. Tyler’s Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. Haworth Herbal Press. 1999, Fourth Ed. Binghamtom, NY 121-124.

Grube B, Grunwald J, Krug L, Staiger C. "Efficacy of a comfrey root (Symphyti offic. Radix) extract ointment in the treatment of patients with painful osteoarthritis of the knee: results of a double-blind, randomized, bicenter, placebo-controlled trial." Phytomedicine. 2007; 14(1): 2-10. 

Kucera M, Barna M, Horacek O, Kalal J, Kucera A, Hladikova M. "Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study." Adv Ther. 2005; 22(6): 681-92.

Kucera M, Barna M, Horacek O, Kovarikova J, Kucera A. "Efficacy and safety of topically applied Symphytum herb extract cream in the treatment of ankle distortion: results of a randomized controlled clinical double blind study." Wien Med Wochenschr. 2004; 154(21-22): 498-507

Koll R., Buhr M, Dieter R, Pabst H, Predel HG, Petrowicz O, Giannetti B, Klingenburg S, Staiger C. "Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distorsions: results of a multicenter, randomized, placebo-controlled, double-blind study." Phytomedicine. 2004; 11(6): 470-7. 

Mills S, Bone K. "Principles and practice of phytotherapy: Modern herbal medicine." Philadelphia: Churchill Livingstone; 2000.

Predel et al. "Efficacy of a comfrey root extract ointment in comparison to a diclofenac gel in the treatment of ankle distortions: results of an observer-blind, randomized, multicenter study." Phytomedicine. 2005 Nov; 12(10): 707-14.

Ridker, P et al. "Hepatic venocclusive disease associated with the consumption of pyrrolizidine-containing dietary supplements." Gastroenterology 1985 Apr; 88(4): 1050-4.

Stickel F, Seitz HK. "The efficacy and safety of comfrey." Public Health Nutr. 2000; 3: 501-508.

von Hildegard B. Hildegard's healing plants. In: Physica. Boston: Beacon Press; 2001. p. 501-8.

Weston, C. et al. "Veno-occlusive disease of the liver secondary to ingestion of comfrey." Br Med J (Clin Res Ed). 1987 July 18; 295 (6591): 183

Yeong M.L., et al. "Hepatic veno-occlusive disease associated with comfrey ingestion." Journal of Gastroenterology and Hepatology, 1990; 5(2): 211-4

Disclaimer 

Information on this website is for educational purposes only. Many herbs historically used for medicine are considered too toxic to use today; some of these herbs have caused deaths. Do not ingest these herbs based on information on this website. We have not provided sufficient information for the safe medicinal use of any of these herbs, nor sufficient information for treatment of poisoning. All recreational use of these herbs is dangerous.