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Other common
name(s): blackwort, bruisewort, common comfrey, knitbone,
slippery root
Scientific/medical
name(s): Symphytum
officinale
Description
Comfrey is a fast-growing herb native to Europe and temperate
parts of Asia. It now grows in North America as well. The roots and
leaves are used in herbal remedies.
Overview
Although comfrey has been used in folk medicine for many years
to help heal wounds, sprains, and fractures, there have been no studies
in humans to prove that it is useful. Available scientific evidence
does not support the idea that comfrey is effective in treating cancer.
It is not considered safe for internal use due to toxic effects on the
liver. There are several varieties of comfrey, some of which contain
more toxic compounds than others.
How is it promoted for use?
Comfrey has been promoted mainly to speed the healing of
wounds, sprains, bruises, and bone fractures and to reduce inflammation
and swelling related to these injuries.
Comfrey has also been used to treat a number of other
ailments, including ulcers, gallstones, arthritis, diarrhea, colitis,
cough, pleurisy, and pneumonia. A mouthwash made from comfrey is
sometimes used for gum disease, hoarseness, and sore throat. Some
proponents also claim comfrey has anti-cancer properties.
What does it involve?
Ointments, salves, and creams that contain comfrey are
available for external use. Compresses and poultices are made from the
crushed roots and leaves of comfrey or from liquid extracts pressed out
of the plant. They are placed directly on bruises, wounds, or sprains,
are covered with a dressing, and are replaced daily until healing
occurs. For internal use, dried comfrey root or leaves are sometimes
prepared as a tea.
In 2001, the U.S. Food and Drug Administration (FDA) asked
manufacturers of dietary supplements to remove products containing
comfrey from the market because of its potential to cause liver damage.
However, whole leaves and roots and extracts of both are still
available. Most comfrey capsules now contain whole-leaf comfrey.
Comfrey can also be purchased to grow at home.
Comfrey has been approved by Commission E (Germany's
regulatory agency for herbs) to be sold only in preparations that
supply no more than 100 micrograms per day if applied to the skin and
no more than 1 microgram of pyrrolizidine alkaloids (toxic compounds in
comfrey) if taken by mouth. This is a tiny amount. For comparison, one
baby aspirin has 80,000 micrograms (or 80 milligrams) of aspirin.
What is the history behind it?
It is reported that comfrey has been used since about 400 BC
for wound healing, inflammation, gout, ulcers, gangrene, burns,
sprains, and fractures. It also was eaten as a vegetable, much like
spinach. In folk medicine, comfrey has been used to treat conditions
such as arthritis, colitis, diarrhea, gallstones, and pleurisy. A few
practitioners tried using comfrey to treat cancer in the twentieth
century.
What is the evidence?
Available scientific evidence does not support claims that
comfrey is useful in curing cancer or any other disease. A few recent
studies that looked at European creams made from comfrey and comfrey
extracts suggested they might be helpful in treating lower back pain,
arthritis, and muscle aches when applied to the skin of the affected
area. At least one study suggested that very high concentrations of the
herb were more helpful than lower concentrations.
When taken internally, comfrey can cause severe liver damage.
Several studies have shown that comfrey contains toxic compounds called
pyrrolizidine alkaloids or PAs, which can cause severe liver damage.
Animal studies have also shown that these chemicals lead to the
development of liver tumors.
Are there any possible problems or
complications?
This substance
may not have been thoroughly tested to find out how it interacts with
medicines, foods, herbs, or supplements. Even though some reports of
interactions and harmful effects may be published, full studies of
interactions and effects are not often available. Because of these
limitations, any information on ill effects and interactions below
should be considered incomplete.
The internal use of comfrey is not considered safe. Experts
strongly warn consumers not to eat or drink anything that contains
comfrey. This herb should be avoided, especially by women who are
pregnant or breastfeeding. The U.S. Pharmacopeia (the U.S. compendium
of quality control tests and information on drugs) reports comfrey
should not be used on broken skin because it may be absorbed into the
body.
In July 2001, the FDA advised supplement manufacturers to
remove products containing comfrey from the market and alert customers
to stop using these products immediately because of the serious health
hazards associated with pyrrolizidine alkaloids. The Federal Trade
Commission has also taken action against unsafe products containing
comfrey. Severe liver damage and even death has occurred with long-term
use. Kidney damage is also possible.
Common comfrey can be easily mistaken for other plants in the
same family, such as Russian comfrey or prickly comfrey, both of which
contain even higher levels of the pyrrolizidine alkaloid toxin.
Poisonings have also been reported when foxglove or other toxic plants
have been mistaken for comfrey.
Allergic reactions to comfrey, while rare, are possible.
Relying on this type of treatment alone and avoiding or delaying
conventional medical care for cancer may have serious health
consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Blumenthal M, ed. The
Complete German Commission E Monographs: Therapeutic Guide to Herbal
Medicines. Austin, TX: American Botanical Council; 1998.
FDA advises dietary supplement manufacturers to remove comfrey
products from the market. July 6, 2001. Center for Food Safety and
Applied Nutrition. US Food and Drug Administration Web site.
http://www.cfsan.fda.gov/~dms/dspltr06.html Accessed June 4, 2008.
Foodborne pathogenic microorganisms and natural toxins
handbook: pyrrolizidine alkaloids. January 1992. Center for Food Safety
and Applied Nutrition. US Food and Drug Administration Web site.
http://www.cfsan.fda.gov/~mow/chap42.html. Accessed June 4, 2008.
Comfrey. British Columbia Cancer Agency Web site.
http://www.bccancer.bc.ca/PPI/UnconventionalTherapies/Comfrey.htm.
Updated February 2000. Accessed June 4, 2008.
Comfrey. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69190.cfm. Accessed June 4, 2008.
Comfrey. University of Maryland Medical Center Web site.
http://www.umm.edu/altmed/ConsHerbs/Comfreych.html. Updated March 15,
2007. Accessed June 4, 2008.
D'Anchise R, Bulitta M, Giannetti B. Comfrey extract ointment
in comparison to diclofenac gel in the treatment of acute unilateral
ankle sprains (distortions). Arzneimittel-Forschung.
2007; 57:712-716.
Grube B, Grünwald 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, randomised, bicenter, placebo-controlled trial. Phytomedicine.
2007;14:2-10.
Gruenwald J. PDR
for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR;
2004.
Fetrow CW, Avila JR. Professional's
Handbook of Complementary & Alternative Medicines.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
Kucera M, Barna M, Horàcek O, Kàlal J,
Kucera A, Hladìkova M. Topical symphytum herb concentrate
cream against myalgia: a randomized controlled double-blind clinical
study. Adv Ther.
2005;22:681-692.
Ridker PM, McDermott WV. Comfrey herb tea and hepatic
veno-occlusive disease. Lancet.1989;1:657-658.
Teynor TM, Putnam DH, Doll JD, Kelling KA, Oelke EA,
Undersander DJ, Oplinger ES. Comfrey. Alternative Field Crops Manual
Web site. http://www.hort.purdue.edu/newcrop/afcm/comfrey.html. Updated
November 17,1997. Accessed June 4, 2008.
Note:
This
information may not cover all possible claims, uses, actions,
precautions, side effects or interactions. It is not intended as
medical advice, and should not be relied upon as a substitute for
consultation with your doctor, who is familiar with your medical
situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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