Comfrey's therapeutic uses

DEFINITION: Natural plant product used to treat specific health conditions.

• PRINCIPAL PROPOSED USES: Back pain, sports injuries (sprains and strains)
• OTHER PROPOSED USES: Broken bones, bruises, varicose veins, open wounds (not recommended), gastrointestinal issues, respiratory problems,

Overview

Comfrey is a high-yielding leafy green plant 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 afterward, 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 and 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 containing herbs such as aloe, goldenseal, calendula, and vitamin E. Such preparations are marketed for the treatment of minor wounds. However, comfrey should not be applied to broken skin for safety reasons. Therefore, it should not be used to treat lacerations or abrasions (cuts and scrapes). There is some evidence that topical comfrey might be useful in treating various conditions involving joint pain or muscles where the skin is unbroken. It may also be helpful in treating skin conditions such as eczema and psoriasis. Comfrey has been suggested as a topical treatment for osteoarthritis. Safety, however, does remain a concern.

In a double-blind, placebo-controlled study of 142 people with acute ankle sprain, the use of comfrey cream for eight days significantly enhanced the recovery rate. Comfrey proved more effective than a placebo in pain, swelling, and mobility measurements. More modest benefits were seen in another double-blind trial, 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 treating back pain. Finally, in a three-week double-blind study of 220 people with knee osteoarthritis, 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 unknown but may include rosmarinic acid, choline, allantoin, and other beneficial compounds, such as tannins, flavonoids, and mucilage.

Comfrey was once suggested for gastrointestinal issues and respiratory problems. However, due to its toxic effects on the liver, internal ingestion is no longer advised.

Safety Issues

As noted above, comfrey contains 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 (hepatic veno-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.

The plant's root generally contains more pyrrolizidine alkaloids than the leaves. Related comfrey species, such as S. uplandicum and S. asperum, contain even higher 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 standard analytic methods used for testing pyrrolizidine alkaloid content may fail to measure a specific 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 it should never be applied to 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. 569-74.

"Comfrey: Herbal Uses, Warnings, Side Effects, Dosage." MedicineNet, www.medicinenet.com/comfrey/article.htm. Accessed 20 Dec. 2025.

"Comfrey - LiverTox." NCBI, 24 May 2022, www.ncbi.nlm.nih.gov/books/NBK548370. Accessed 20 Dec. 2025.

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. 681-92.

Kuchta, Kenny, and Mathias Schmidt. "Safety of Medicinal Comfrey Cream Preparations (Symphytum Officinale S.L.): The Pyrrolizidine Alkaloid Lycopsamine Is Poorly Absorbed through Human Skin." Regulatory Toxicology and Pharmacology, vol. 118, 2020, p. 104784, doi.org/10.1016/j.yrtph.2020.104784. Accessed 20 Dec. 2025.

Nunn, Megan. "What Is Comfrey Cream?" Verywell Health, 20 Aug. 2025, www.verywellhealth.com/the-benefits-of-comfrey-ointment-88624. Accessed 20 Dec. 2025.

Pabst, Helmut, 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." Phytotherapy Research, vol. 27, no. 6, 2013, pp. 811-7, doi.org/10.1002/ptr.4790. Accessed 20 Dec. 2025.