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Comfrey

Common names: Knitbone, Boneset

Botanical name: Symphytum officinale

Photo

© Martin Wall

Parts used and where grown

The leaf and root of comfrey have been employed medicinally for centuries. Originally from Europe and western Asia, it is now also grown in North America.

Comfrey has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns
2Stars

Sprains (topical)

1Star

Broken bones (topical)

Bruises (topical)

Chronic skin ulcer (topical)

Conjunctivitis/blepharitis (topical eye application)

Cough

Peptic ulcer

Thrombophlebitis (topical)

Wound healing (topical)

3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies)

Comfrey has a long history of use as a topical agent for treating wounds, skin ulcers, thrombophlebitis, bruises, and sprains and strains.1 2 Comfrey was used by herbalists to promote more rapid repair of broken bones, hence the common names boneset and knitbone. Topically, comfrey was also used to treat minor skin irritations and inflammation. It has also been used as a wash or topical application for eye irritations and for treating conjunctivitis. Internally, it was used to treat gastrointestinal problems, such as stomach ulcers and inflammatory bowel disease, and lung problems.

Active constituents: Mucilage and allantoin are considered the major constituents in comfrey responsible for the herbs soothing and anti-inflammatory actions.3

How much is usually taken?

Fresh, peeled root or dried root, approximately 3.5 ounces (100 grams), is simmered in 1 pint (500 ml) of water for ten to fifteen minutes to prepare comfrey for topical use.4 Cloth or gauze is soaked in this liquid, then applied to the skin for at least 15 minutes. Fresh leaves can be ground up lightly and applied directly to the skin. Alternatively, creams or ointments made from root or leaf can be applied. All topical preparations should be applied several times per day.

Due to variations in pyrrolizidine alkaloid content, root preparations are unsafe for internal use unless they are guaranteed pyrrolizidine-free. Although comfrey root tea has been used traditionally, the danger of its pyrrolizidine alkaloids is significant. Therefore, comfrey root and young leaf preparations should not be taken internally.

Are there any side effects or interactions?

Comfrey contains potentially dangerous compounds known as pyrrolizidine alkaloids. The roots contain higher levels of these compounds and mature leaves contain very little, if any, of these alkaloids.5 6 Fresh young leaves contain higher amounts (up to 16 times more than mature leaves) and should be avoided.7 Other related forms, such as Russian comfrey (Symphytum uplandicum) and prickly comfrey (S. asperum), are sometimes available or mistakenly sold as regular comfrey but contain higher levels of these alkaloids.8 Several cases of people who developed liver disease or other serious problems from taking capsules or tea of comfrey have been reported over the years.9

Most comfrey products do not list their pyrrolizidine alkaloid content on the label. Therefore, it is best to avoid internal use of products made from comfrey root or young leaves altogether.

At the time of writing, there were no well-known drug interactions with comfrey.

References:

1. Mills SY. Out of the Earth: The Essential Book of Herbal Medicine. New York: Viking Arkana, 1991, 544–7.

2. Weiss RF. Herbal Medicine. Gothenburg, Sweden: Ab Arcanum and Beaconsfield, UK: Beaconsfield Publishers Ltd., 1988, 334–5.

3. Duke JA. Handbook of Phytochemical Constituents of GRAS Herbs and Other Economic Plants. Boca Raton, FL: CRC Press, 1992.

4. Weiss RF. Herbal Medicine. Gothenburg, Sweden: Ab Arcanum and Beaconsfield, UK: Beaconsfield Publishers Ltd., 1988, 334–5.

5. Mills SY. Out of the Earth: The Essential Book of Herbal Medicine. New York: Viking Arkana, 1991, 544–7.

6. Winship KA. Toxicity of comfrey. Adverse Drug React Toxicol Rev 1991;10:47–59 [review].

7. Foster S. Herbal Renaissance. Salt Lake City: Gibbs-Smith Publisher, 1993, 74–8.

8. Foster S. Herbal Renaissance. Salt Lake City: Gibbs-Smith Publisher, 1993, 74–8.

9. Foster S, Tyler VE. Tyler’s Honest Herbal. New York: Haworth Herbal Press, 1999, 121–6.

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