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Also listed as: Knitbone; Symphytum officinale

Plant Description
What's It Made Of?
Available Forms
How to Take It
Possible Interactions
Supporting Research


Comfrey (Symphytum officinale) has been used on the skin to treat wounds and reduce the inflammation from sprains and broken bones. Comfrey roots and leaves contain allantoin, a substance that helps new skin cells grow, along with other substances that reduce inflammation and keep skin healthy. Comfrey ointments were often applied to the skin to heal bruises as well as pulled muscles and ligaments, fractures, sprains, strains, and osteoarthritis.

In the past, comfrey was also used to treat stomach problems. However, the herb contains dangerous substances called pyrrolizidine alkaloids that are very toxic to the liver and can cause death. The U.S. Food and Drug Administration no longer allows any oral comfrey products to be sold in the U.S. The United Kingdom, Australia, Canada, and Germany also have banned the sale of oral products containing comfrey.

The dangerous substances in comfrey are also absorbed through the skin, and harmful amounts may build up in the body. You should be careful if you use an ointment containing comfrey (see "How to Take It" section), and you should never use it on broken skin.

Plant Description

Comfrey is a perennial shrub that is native to Europe and temperate parts of Asia. Fond of moist soils, comfrey has a thick, hairy stem, and grows 2 - 5 feet tall. Its flowers are dull purple, blue or whitish, and densely arranged in clusters. The leaves are oblong, and often look different depending upon their position on the stem: Lower leaves are broad at the base and tapered at the ends while upper leaves are broad throughout and narrow only at the ends. The root has a black outside and fleshy whitish interior filled with juice.

Comfrey preparations are made from the leaves or other parts of the plant grown above the ground. New leaves tend to have more of the poisonous pyrrolizidine alkaloids than older leaves. Some preparations were also made from the roots, but roots contain up to 16 times the amount of pyrrolizidine alkaloids.

What's It Made Of?

Comfrey contains substances that help skin regenerate, including allantoin, rosmarinic acid, and tannins. It also contains poisonous compounds called pyrrolizidine alkaloids.

Available Forms

Oral comfrey products have been banned in the U.S. and many European countries, but you can still find products for use on the skin.

Comfrey ointments (containing 5 - 20% comfrey), creams, poultices, and liniments are made from the fresh or dried herb, leaf, or root of comfrey species. Use only products made from leaves of common comfrey.

Be sure to buy comfrey products from companies with good reputations. Follow dosage recommendations below.

How to Take It


Never give a child comfrey by mouth. Do not apply creams or ointments containing comfrey to a child's skin.


  • Never take comfrey by mouth. Severe liver poisoning and even death may occur.
  • When using herb and leaf ointments, creams, and other topical preparations, it's important to follow these safety recommendations:
  • Never apply comfrey to broken skin.
  • Use only small amounts of comfrey-containing creams for no longer than 10 days at a time.
  • Do not use any comfrey product for more than 4 - 6 total weeks in a year.


Comfrey contains toxic substances that can cause severe liver damage and possibly even death. Comfrey and products that contain comfrey should never be taken orally.

Comfrey contains toxic substances that can be absorbed by the skin. Even topical preparations should be used for only a short time, and under the supervision of your health care provider.

Comfrey should never be applied to open wounds or broken skin.

Do not use comfrey if you have liver disease, alcoholism, or cancer.

Children, the elderly, and pregnant or breastfeeding women should not use any comfrey products -- even topical ones.

Possible Interactions

Because it may raise the risk of liver damage, comfrey should not be used with other medications that may also affect the liver, such as acetaminophen (Tylenol). If you take any medications, whether prescription or over the counter, ask your doctor before using comfrey.

You should not use some herbs that have also been known to cause liver problems, such as kava, skullcap, and valerian, while using comfrey ointment or cream because it raises the risk for liver damage.

Supporting Research

Bleakley CM, McDonough SM, MacAuley DC. Some conservative strategies are effective when added to controlled mobilisation with external support after acute ankle sprain: a systematic review. Aust J Physiother. 2008;54(1):7-20.

Blumenthal M, Busse WR, Goldberg A, et al., ed. The Complete German Commission E Monograph; Therapeutic Guide to Herbal Medicines. Boston. Mass: Integrative Medicine Communications; 1998:115-116.

Cirigliano M, Sun A. Advising patients about herbal therapies. JAMA. 1998;280(18):1565-1566.

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

Grube B, Grunwald J, Krug L, Staiger C. Efficacy of 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(1):2-10.

Gruenwald J, Brendler T, Jaenicke C, eds. PDR for Herbal Medicines. 2nd ed. Montvale, NJ: Medical Economics Co; 2000:212-213.

Koll R, Klingenburg S. Therapeutic characteristance and tolerance of topical comfrey preparations. Results of an observational study of patients. Fortschr Med Orig. 2002;120(1):1-9.

Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med. 1998;158(20):2200-2211.

Miskelly FG, Goodyer LI. Hepatic and pulmonary complications of herbal medicines. Postgrad Med J. 1992;68:935-936.

Newall CA, Anderson LA, Phillipson JD. eds. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press; 1996:87-89.

Ridker PM, Ohkuma S, McDermott WV, Trey C, Huxtable RJ. Hepatic venocclusive disease associated with the consumption of pyrrolizidine-containing dietary supplements. Gastroenterology. 1985;(88):1050-1054.

Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr. 2000;3(4A):501-508.

Weston CFM, Cooper BT, Davies JD, et al. Veno-occlusive disease of the liver secondary to ingestion of comfrey. Br Med J. 1987;295:183.

Yeong ML, Swinburn B, Kennedy M, Nicholson G. Hepatic veno-occlusive disease associated with comfrey ingestion. J Gastroenterol Hepatol. 1990;5(2):211-214.

Review Date: 1/2/2011
Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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