Comfrey's therapeutic uses
Comfrey, a leafy green plant historically utilized for its medicinal properties, has been associated with various therapeutic uses, particularly in topical applications. Traditionally, it was believed to aid in bone healing and was used for conditions such as digestive and lung issues. Today, comfrey creams are often applied to alleviate symptoms of osteoarthritis, gout, minor wounds, and muscle or joint pain. Research indicates that topical comfrey may enhance recovery from sprains and reduce symptoms in osteoarthritis patients, though its safety profile raises significant concerns.
Despite its potential benefits, comfrey is known to contain toxic pyrrolizidine alkaloids, which can lead to severe liver damage and even death when ingested or improperly used. Consequently, it was banned as an oral supplement in the U.S. and is cautioned against for use on broken skin. Experts recommend limiting topical use to short durations and advise against usage for vulnerable populations such as children and pregnant women. Given these risks, individuals interested in comfrey should proceed with caution and seek guidance on safe applications.
Comfrey's therapeutic uses
Definition: Natural plant product used to treat specific health conditions.
Principal proposed uses: Back pain, sports injures (sprains and strains)
Other proposed uses: Broken bones, bruises, varicose veins, open wounds (not recommended)
Overview
Comfrey is a high-yielding leafy green plant that has been used for centuries as a feed crop for animals and a medicine for humans. However, in 2001, it was removed as an oral dietary supplement from the American market, and soon afterwards, it was removed as a commercial animal food source. These actions were taken because comfrey contains dangerous levels of toxic pyrrolizidine alkaloids, and its use has led to severe liver injury and death.
Traditionally, oral or topical use of comfrey was said to help bones heal more rapidly, and this is the origin of its Latin name Symphytum (“drawing together”). It was also used orally for the treatment of digestive and lung problems. Topical comfrey creams have been used to treat osteoarthritis, gout, minor wounds, bruises, sprains, and varicose veins.
Therapeutic Dosages
The tested form of topical comfrey contains 10 percent of a 2.5:1 juice extract made from fresh pressed plant sap. In other words, every 100 grams (g) of cream contains the equivalent of 25 g of comfrey sap.
Therapeutic Uses
Comfrey is commonly included in salves and creams that also contain such herbs as aloe, goldenseal, calendula, and vitamin E. Such preparations are marketed for treatment of minor wounds. However, for safety reasons, comfrey should not be applied to broken skin. Therefore, it should not be used for the treatment of lacerations or abrasions (cuts and scrapes). There is some evidence that topical comfrey might be useful in the treatment of various conditions involving pain in the joints or muscles where skin is unbroken. Safety, however, does remain a concern.
In a double-blind, placebo-controlled study of 142 people with acute ankle sprain, use of comfrey cream for eight days significantly enhanced the rate of recovery. Comfrey proved more effective than a placebo in measurements of pain, swelling, and mobility. More modest benefits were seen in another double-blind trial, this one enrolling 203 people with an ankle sprain and comparing a high-comfrey product to a low-comfrey product.
Another double-blind, placebo-controlled study, this one enrolling 215 people, found comfrey cream helpful for treatment of back pain. Finally, in a three-week double-blind study of 220 people with osteoarthritis of the knee, comfrey cream reduced symptoms significantly more than a placebo cream.
In a well-designed trial, two concentrations of comfrey creams were evaluated for the treatment of fresh abrasions among 278 patients (almost one-quarter of whom were under age twenty). The higher-concentration cream (10 percent) contained ten times more comfrey than the low-concentration cream (considered the reference or placebo cream). The 10 percent comfrey cream led to significantly faster wound healing than the reference cream after two to three days of application. Although the researchers reported no adverse effects in either group, the use of comfrey has been associated with severe and even life-threatening, toxic effects when used orally, and its use over open wounds should be undertaken with extreme caution.
Additional studies, generally of lower quality, suggest possible benefits for shoulder tendonitis and knee injuries. The active ingredients in comfrey are not known but may include rosmarinic acid, choline, and allantoin.
Safety Issues
As noted above, comfrey contains substances called pyrrolizidine alkaloids that are both toxic to the liver and carcinogenic. The main form of liver disease seen with comfrey is a blockage of small veins that can lead to liver cirrhosis and eventually liver failure (hepato-occlusive disease). Liver transplantation may be required. Oral use of comfrey for as brief a time as five to seven days in a child and nineteen to forty-five days in adults has resulted in severe liver disease and death. Long-term use of very low dosages may also cause harm.
In general, the root of the plant contains more pyrrolizidine alkaloids than the leaves. Related species of comfrey such as S. uplandicum and S. asperum contain even higher levels of these toxins and may be mistakenly sold as ordinary comfrey.
Pyrrolizidine alkaloids in comfrey can be absorbed through the skin. For this reason, it has been recommended that when using comfrey preparations, the daily amount of pyrrolizidine alkaloids should not exceed 100 micrograms (mcg). Few products are labeled to indicate their pyrrolizidine alkaloid content. Furthermore, the common analytic methods used for testing pyrrolizidine alkaloid content may fail to measure a certain chemical form of these toxins (the N-oxide form), leading to results that are too low by a factor of ten or more. For all these reasons, it may be prudent to avoid topical comfrey products entirely. If comfrey is used as a topical treatment, experts recommend that it not be applied for more than four to six weeks per year or more than ten days in a row and that it never be applied on broken skin. In addition, comfrey should not be used by children, pregnant or nursing women, or people with liver disease.
Bibliography
Barna, M., et al. “Wound Healing Effects of a Symphytum Herb Extract Cream.” Wiener Medenzinische Wochenschrift, vol. 157, 2007, pp. 569-574.
"Comfrey." National Library of Medicine, 24 May 2022, www.ncbi.nlm.nih.gov/books/NBK548370. Accessed 20 Aug. 2023.
Grube, B., et al. “Efficacy of a Comfrey Root (Symphyti offic. radix) Extract Ointment in the Treatment of Patients with Painful Osteoarthritis of the Knee.” Phytomedicine, vol. 14, no. 1, 2007, pp. 2-10.
Kucera, M., et al. “Topical Symphytum Herb Concentrate Cream Against Myalgia.” Advances in Therapy, vol. 22, 2005, pp. 681-692.
Nunn, Megan. "What Is Comfrey Cream?" Verywell Health, 22 June 2023, www.verywellhealth.com/the-benefits-of-comfrey-ointment-88624. Accessed 20 Aug. 2022.
Pabst, H., et al. "Combination of Comfrey Root Extract Plus Methyl Nicotinate in Patients with Conditions of Acute Upper or Low Back Pain: A Multicentre Randomised Controlled Trial." Phytother Res., vol. 27, 2013, no. 6, pp. 811-817. doi:10.1002/ptr.4790.