- What other names is Comfrey known by?
- What is Comfrey?
- How does Comfrey work?
- Are there safety concerns?
- Are there any interactions with medications?
- Dosing considerations for Comfrey.
Ass Ear, Black Root, Blackwort, Bruisewort, Common Comfrey, Consolidae Radix, Consound, Consoude, Consoude Officinale, Consuelda, Grande Consoude, Gum Plant, Healing Herb, Herbe aux Charpentiers, Herbe à la Coupure, Knitback, Knitbone, Langue-de-Vache, Oreille d'Âne, Salsify, Slippery Root, Symphytum officinale, Wallwort.
Comfrey is a plant. Even though this plant contains poisonous chemicals called pyrrolizidine alkaloids (PAs), the leaf, root, and root-like stem (rhizome) are used to make medicine. The amount of PAs found in comfrey changes according to the time of harvesting and the age of the plant. The roots have 10 times higher amounts of PAs than the leaves. Some products labeled “common comfrey” or Symphytum officinale actually contain the more poisonous “prickly comfrey” (Symphytum asperum) or “Russian comfrey” (Symphytum x uplandicum) species.
Comfrey is used as a tea for upset stomach, ulcers, heavy menstrual periods, diarrhea, bloody urine, persistent cough, painful breathing (pleuritis), bronchitis, cancer, and chest pain (angina). It is also used as a gargle for gum disease and sore throat.
Possibly Effective for...
- Back pain. Applying a specific comfrey extract (Kytta-Salbe f by Merck Selbstmedikation GmbH) to the affected area for 5 days seems to decrease lower or upper back pain.
- Osteoarthritis. Applying a specific comfrey extract (Kytta-Salbe f) to the affected area for 3 weeks or applying a specific cream containing comfrey extract, tannic acid, Aloe vera gel, eucalyptus oil, and frankincense oil (4Jointz) to the affected are for 12 weeks seems to decrease pain in people with knee osteoarthritis.
- Sprains. Early research suggests that applying comfrey ointment to the affected area for up to 2 weeks improves mobility, decreases pain, and reduces tenderness and swelling of sprains. The effect of comfrey ointment in relieving pain and reducing swelling seems to be comparable to the effects of diclofenac gel. Most of the studies have used a specific comfrey ointment that is low in pyrrolizidine alkaloids (Kytta-Salbe f).
Insufficient Evidence to Rate Effectiveness for...
- Bruises. Early research suggests that applying comfrey directly to the skin for 2 weeks might decrease pain and tenderness of bruises.
- Skin ulcers.
- Broken bones.
- Heavy menstrual periods.
- Sore throat.
- Gum disease.
- Joint pain.
- Chest pain.
- Inflammation (pain and swelling).
- Other conditions.
The chemicals in comfrey might have a healing effect and reduce inflammation when applied to the skin. However, comfrey contains toxic chemicals that can be absorbed through the skin.
Comfrey is POSSIBLY SAFE for most people when applied to unbroken skin in small amounts for less than 10 days. It's important to remember that the poisonous chemicals in comfrey can pass through the skin. Absorption of these chemicals increases if the skin is broken or if large amounts are applied.
Comfrey is LIKELY UNSAFE for anyone when taken by mouth. It contains chemicals (pyrrolizidine alkaloids, PAs) that can cause liver damage, lung damage, and cancer. The FDA has recommended removal of oral comfrey products from the market.
Special Precautions & Warnings:Pregnancy and breast-feeding: Comfrey is LIKELY UNSAFE to take by mouth or apply to the skin if you are pregnant or breast-feeding. In addition to causing liver damage and possibly cancer, the PAs in comfrey might also cause birth defects. Even topical use is unwise, since the PAs can be absorbed through the skin.
Broken or damaged skin: Don't apply comfrey to broken or damaged skin. Doing so might expose you to large amounts of the chemicals in comfrey that can cause liver damage and other serious health effects.
Liver disease: There is a concern that comfrey might make liver disease worse. Don't use comfrey if you have any problems with your liver.
Medications that can harm the liver (Hepatotoxic drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Comfrey might harm the liver. Taking comfrey along with medication that might also harm the liver can increase the risk of liver damage. Do not take comfrey if you are taking a medication that can harm the liver.
Some medications that can harm the liver include acetaminophen (Tylenol and others), amiodarone (Cordarone), carbamazepine (Tegretol), isoniazid (INH), methotrexate (Rheumatrex), methyldopa (Aldomet), fluconazole (Diflucan), itraconazole (Sporanox), erythromycin (Erythrocin, Ilosone, others), phenytoin (Dilantin), lovastatin (Mevacor), pravastatin (Pravachol), simvastatin (Zocor), and many others.
Medications that increase the breakdown of other medications by the liver (Cytochrome P450 3A4 (CYP3A4) inducers)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Comfrey is broken down by the liver. Some chemicals that form when the liver breaks down comfrey can be harmful. Medications that cause the liver to break down comfrey might increase the toxic effects of chemicals contained in comfrey.
The appropriate dose of comfrey depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for comfrey. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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Abbott, P. J. Comfrey: assessing the low-dose health risk. Med.J.Aust. 12-5-1988;149(11-12):678-682. View abstract.
Aftab, K., Shaheen, F., Mohammad, F. V., Noorwala, M., and Ahmad, V. U. Phyto-pharmacology of saponins from Symphytum officinale L. Adv Exp Med Biol 1996;404:429-442. View abstract.
Ahmad, V. U., Noorwala, M., Mohammad, F. V., and Sener, B. A new triterpene glycoside from the roots of Symphytum officinale. J Nat Prod. 1993;56(3):329-334. View abstract.
Altamirano, J. C., Gratz, S. R., and Wolnik, K. A. Investigation of pyrrolizidine alkaloids and their N-oxides in commercial comfrey-containing products and botanical materials by liquid chromatography electrospray ionization mass spectrometry. J AOAC Int 2005;88(2):406-412. View abstract.
Barbakadze, V. V., Kemertelidze, E. P., Targamadze, I. L., Shashkov, A. S., and Usov, A. I. [Novel biologically active polymer of 3-(3,4-dihydroxyphenyl)glyceric acid from two types of the comphrey Symphytum asperum and S. caucasicvum (Boraginoceae)]. Bioorg.Khim. 2002;28(4):362-366. View abstract.
Barna, M., Kucera, A., Hladicova, M., and Kucera, M. [Wound healing effects of a Symphytum herb extract cream (Symphytum x uplandicum NYMAN: ): results of a randomized, controlled double-blind study]. Wien.Med.Wochenschr. 2007;157(21-22):569-574. View abstract.
Barna, M., Kucera, A., Hladikova, M., and Kucera, M. Randomized double-blind study: wound-healing effects of a Symphytum herb extract cream (Symphytumxuplandicum Nyman) in children. Arzneimittelforschung. 2012;62(6):285-289. View abstract.
Barthomeuf, C. M., Debiton, E., Barbakadze, V. V., and Kemertelidze, E. P. Evaluation of the dietetic and therapeutic potential of a high molecular weight hydroxycinnamate-derived polymer from Symphytum asperum Lepech. Regarding its antioxidant, antilipoperoxidant, antiinflammatory, and cytotoxic properties. J Agric.Food Chem 2001;49(8):3942-3946. View abstract.
Behninger, C., Abel, G., Roder, E., Neuberger, V., and Goggelmann, W. [Studies on the effect of an alkaloid extract of Symphytum officinale on human lymphocyte cultures]. Planta Med. 1989;55(6):518-522. View abstract.
Betz, J. M., Eppley, R. M., Taylor, W. C., and Andrzejewski, D. Determination of pyrrolizidine alkaloids in commercial comfrey products (Symphytum sp.). J Pharm Sci 1994;83(5):649-653. View abstract.
Bleakley, C. M., McDonough, S. M., and MacAuley, D. C. 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. View abstract.
Brauchli, J., Luthy, J., Zweifel, U., and Schlatter, C. Pyrrolizidine alkaloids from Symphytum officinale L. and their percutaneous absorption in rats. Experientia 9-15-1982;38(9):1085-1087. View abstract.
Couet, C. E., Crews, C., and Hanley, A. B. Analysis, separation, and bioassay of pyrrolizidine alkaloids from comfrey (Symphytum officinale). Nat.Toxins. 1996;4(4):163-167. View abstract.
Culvenor, C. C., Clarke, M., Edgar, J. A., Frahn, J. L., Jago, M. V., Peterson, J. E., and Smith, L. W. Structure and toxicity of the alkaloids of Russian comfrey (symphytum x uplandicum Nyman), a medicinal herb and item of human diet. Experientia 4-15-1980;36(4):377-379. View abstract.
D'Anchise, R., Bulitta, M., and Giannetti, B. Comfrey extract ointment in comparison to diclofenac gel in the treatment of acute unilateral ankle sprains (distortions). Arzneimittelforschung. 2007;57(11):712-716. View abstract.
Dasgupta, A. Review of abnormal laboratory test results and toxic effects due to use of herbal medicines. Am J Clin Pathol 2003;120(1):127-137. View abstract.
Di Mambro, V. M. and Fonseca, M. J. Assays of physical stability and antioxidant activity of a topical formulation added with different plant extracts. J Pharm Biomed Anal. 2-23-2005;37(2):287-295. View abstract.
Dolganiuc, A., Radu, L. D., and Olinescu, A. [The effect of products of plant and microbial origin on phagocytic function and on the release of oxygen free radicals by mouse peritoneal macrophages]. Bacteriol.Virusol.Parazitol.Epidemiol. 1997;42(1-2):65-69. View abstract.
Fijalkowski, D. and Seroczynska, M. Herba ol. 1977;23:47.
Franz, G. [Studies on the mucopolysaccharides of Tussilago farfara L., Symphytum officinalis L., Borago officinalis L. and Viola tricolor L]. Planta Med 1969;17(3):217-220. View abstract.
FRIES, B. [Obstructive ileus after ingestion of comfrey (radix Symphyti).]. Sven.Lakartidn. 10-2-1953;50(40):2085-2087. View abstract.
Furmanowa, M., Guzewska, J., and Beldowska, B. Mutagenic effects of aqueous extracts of Symphytum officinale L. and of its alkaloidal fractions. J Appl Toxicol 1983;3(3):127-130. View abstract.
Furuya, T. and Araki, K. Studies on constituents of crude drugs. I. Alkaloids of Symphytum officinale Linn. Chem Pharm Bull.(Tokyo) 1968;16(12):2512-2516. View abstract.
Giannetti, B. M., Staiger, C., Bulitta, M., and Predel, H. G. Efficacy and safety of comfrey root extract ointment in the treatment of acute upper or lower back pain: results of a double-blind, randomised, placebo controlled, multicentre trial. Br.J Sports Med. 2010;44(9):637-641. View abstract.
Gray, D. E., Porter, A., O'Neill, T., Harris, R. K., and Rottinghaus, G. E. A rapid cleanup method for the isolation and concentration of pyrrolizidine alkaloids in comfrey root. J AOAC Int 2004;87(5):1049-1057. View abstract.
Grube, B., Grunwald, J., Krug, L., and 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(1):2-10. View abstract.
Gyorik, S. and Stricker, H. Severe pulmonary hypertension possibly due to pyrrolizidine alkaloids in polyphytotherapy. Swiss.Med.Wkly. 4-4-2009;139(13-14):210-211. View abstract.
Hirono, I., Mori, H., and Haga, M. Carcinogenic activity of Symphytum officinale. J Natl.Cancer Inst 1978;61(3):865-869. View abstract.
Huxtable, R. J., Luthy, J., and Zweifel, U. Toxicity of comfrey-pepsin preparations. N.Engl.J.Med. 10-23-1986;315(17):1095. View abstract.
Ishigami, R., Shiotani, H., Yoshida, A., Kawata, T., and Natori, H. [A comfrey phytobezoar; a case report]. Naika Hokan 1967;14(9):291-294. View abstract.
Johnson, B. M., Bolton, J. L., and van Breemen, R. B. Screening botanical extracts for quinoid metabolites. Chem Res Toxicol 2001;14(11):1546-1551. View abstract.
Karavaev, V. A., Solntsev, M. K., Iurina, T. P., Iurina, E. V., Poliakova, I. B., and Kuznetsov, A. M. [Antifungal activity of aqueous extracts from the leaf of cowparsnip and comfrey]. Izv.Akad.Nauk Ser.Biol 2001;(4):435-441. View abstract.
Kim, N. C., Oberlies, N. H., Brine, D. R., Handy, R. W., Wani, M. C., and Wall, M. E. Isolation of symlandine from the roots of common comfrey (Symphytum officinale) using countercurrent chromatography. J Nat Prod. 2001;64(2):251-253. View abstract.
Koll, R., Buhr, M., Dieter, R., Pabst, H., Predel, H. G., Petrowicz, O., Giannetti, B., Klingenburg, S., and Staiger, C. Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distorsions: results of a multicenter, randomized, placebo-controlled, double-blind study. Phytomedicine. 2004;11(6):470-477. View abstract.
Koll, R., Buhr, M., Dieter, R., Petrowicz, O., Gianetti, B., and Wagener, S. Wirksamkeit und Vertraglichkeit von Beinwellextrakt (Extr. Rad. Symphyti) bei Sprunggelenks-distorsionen. Z Phytotherapie 2000;21:127-134.
Kucera, M., Barna, M., Horacek, O., Kalal, J., Kucera, A., and Hladikova, M. Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study. Adv Ther 2005;22(6):681-692. View abstract.
Kucera, M., Barna, M., Horacek, O., Kovarikova, J., and Kucera, A. Efficacy and safety of topically applied Symphytum herb extract cream in the treatment of ankle distortion: results of a randomized controlled clinical double blind study. Wien.Med Wochenschr. 2004;154(21-22):498-507. View abstract.
Kucera, M., Kalal, J., and Polesna, Z. Effects of Symphytum ointment on muscular symptoms and functional locomotor disturbances. Adv.Ther 2000;17(4):204-210. View abstract.
Larrey, D. [Liver involvement in the course of phytotherapy]. Presse Med 4-16-1994;23(15):691-693. View abstract.
Laslett, L. L., Quinn, S. J., Darian-Smith, E., Kwok, M., Fedorova, T., Korner, H., Steels, E., March, L., and Jones, G. Treatment with 4Jointz reduces knee pain over 12 weeks of treatment in patients with clinical knee osteoarthritis: a randomised controlled trial. Osteoarthritis.Cartilage. 2012;20(11):1209-1216. View abstract.
Lewis, C. J. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. 7-6-2001;
Lin, C. C., Yang, C. C., Phua, D. H., Deng, J. F., and Lu, L. H. An outbreak of foxglove leaf poisoning. J Chin Med.Assoc. 2010;73(2):97-100. View abstract.
Mackinnon, M. In general practice, 'always expect the unexpected'. Aust.Fam.Physician 2008;37(4):235-236. View abstract.
Makarova, G. V. and et al. Farm.Zh. 1966;21(5):41.
Mazzocchi, A. and Montanaro, F. Observational study of the use of Symphytum 5CH in the management of pain and swelling after dental implant surgery. Homeopathy. 2012;101(4):211-216. View abstract.
McDermott, W. V. and Ridker, P. M. The Budd-Chiari syndrome and hepatic veno-occlusive disease. Recognition and treatment. Arch Surg. 1990;125(4):525-527. View abstract.
Mei, N., Guo, L., Fu, P. P., Heflich, R. H., and Chen, T. Mutagenicity of comfrey (Symphytum Officinale) in rat liver. Br J Cancer 3-14-2005;92(5):873-875. View abstract.
Mohammad, F. V., Noorwala, M., Ahmad, V. U., and Sener, B. A bidesmosidic hederagenin hexasaccharide from the roots of Symphytum officinale. Phytochemistry 1995;40(1):213-218. View abstract.
New South Wales Health, Australia. Amendments to the poison list. Poisons Legislation Circular 3-22-1993;60
Noorwala, M., Mohammad, F. V., Ahmad, V. U., and Sener, B. A bidesmosidic triterpene glycoside from the roots of Symphytum officinale. Phytochemistry 1994;36(2):439-443. View abstract.
Oberlies, N. H., Kim, N. C., Brine, D. R., Collins, B. J., Handy, R. W., Sparacino, C. M., Wani, M. C., and Wall, M. E. Analysis of herbal teas made from the leaves of comfrey (Symphytum officinale): reduction of N-oxides results in order of magnitude increases in the measurable concentration of pyrrolizidine alkaloids. Public Health Nutr 2004;7(7):919-924. View abstract.
Olinescu, A., Manda, G., Neagu, M., Hristescu, S., and Dasanu, C. Action of some proteic and carbohydrate components of Symphytum officinale upon normal and neoplastic cells. Roum.Arch.Microbiol.Immunol. 1993;52(2):73-80. View abstract.
Predel, H. G., Giannetti, B., Koll, R., Bulitta, M., and Staiger, C. Efficacy of a comfrey root extract ointment in comparison to a diclofenac gel in the treatment of ankle distortions: results of an observer-blind, randomized, multicenter study. Phytomedicine 2005;12(10):707-714. View abstract.
Ramlau, J. [Budd-Chiari syndrome after herbal tea?]. Ugeskr.Laeger 8-19-2002;164(34):3979. View abstract.
Ridker, P. M. and McDermott, W. V. Comfrey herb tea and hepatic veno-occlusive disease. Lancet 3-25-1989;1(8639):657-658. View abstract.
Ridker, P. M., Ohkuma, S., McDermott, W. V., Trey, C., and Huxtable, R. J. Hepatic venocclusive disease associated with the consumption of pyrrolizidine-containing dietary supplements. Gastroenterology 1985;88(4):1050-1054. View abstract.
Ridker, P. N. and McDermont, W. V. Hepatotoxicity due to comfrey herb tea. Am.J.Med. 1989;87(6):701. View abstract.
Satake, M. [Safety information of healthy food used in Japan]. Shokuhin Eiseigaku Zasshi 2010;51(6):408-414. View abstract.
Schaneberg, B. T., Molyneux, R. J., and Khan, I. A. Evaporative light scattering detection of pyrrolizidine alkaloids. Phytochem.Anal. 2004;15(1):36-39. View abstract.
Staiger, C. Comfrey: a clinical overview. Phytother.Res 2012;26(10):1441-1448. View abstract.
Stamford, I. F. and Tavares, I. A. The effect of an aqueous extract of comfrey on prostaglandin synthesis by rat isolated stomach. J Pharm Pharmacol 1983;35(12):816-817. View abstract.
Summers, R. S. Cardiotoxic principle in comfrey. S.Afr.Med J 1-13-1979;55(2):37. View abstract.
Tanret, I. and Duh, D. [Pharmaceutical sheet. Symphytum officinale L., dermal use (Flexagile cream)]. J Pharm.Belg. 2012;(1):41-42. View abstract.
Tunon, H., Olavsdotter, C., and Bohlin, L. Evaluation of anti-inflammatory activity of some Swedish medicinal plants. Inhibition of prostaglandin biosynthesis and PAF-induced exocytosis. J Ethnopharmacol 1995;48(2):61-76. View abstract.
Turley, A. J. and Muir, D. F. ECG for physicians: a potentially fatal case of mistaken identity. Resuscitation 2008;76(3):323-324. View abstract.
Ulubelen, A. and Doganca, S. Anadoline, a new senecio alkaloid from symphytum orientale. Tetrahedron Lett 1970;30:2583-2585. View abstract.
Wagner, H., Horhammer, L., and Frank, U. [Lithospermic acid, the antihormonally active principle of Lycopus europaeus L. and Symphytum officinale. 3. Ingredients of medicinal plants with hormonal and antihormonal-like effect]. Arzneimittelforschung 1970;20(5):705-713. View abstract.
Weston, C. F., Cooper, B. T., Davies, J. D., and Levine, D. F. Veno-occlusive disease of the liver secondary to ingestion of comfrey. Br.Med.J.(Clin.Res.Ed) 7-18-1987;295(6591):183. View abstract.
Williams, L., Chou, M. W., Yan, J., Young, J. F., Chan, P. C., and Doerge, D. R. Toxicokinetics of riddelliine, a carcinogenic pyrrolizidine alkaloid, and metabolites in rats and mice. Toxicol Appl Pharmacol 7-15-2002;182(2):98-104. View abstract.
Winship, K. A. Toxicity of comfrey. Adverse Drug React.Toxicol.Rev. 1991;10(1):47-59. View abstract.
Yeong, M. L., Clark, S. P., Waring, J. M., Wilson, R. D., and Wakefield, S. J. The effects of comfrey derived pyrrolizidine alkaloids on rat liver. Pathology 1991;23(1):35-38. View abstract.
Yeong, M. L., Wakefield, S. J., and Ford, H. C. Hepatocyte membrane injury and bleb formation following low dose comfrey toxicity in rats. Int J Exp Pathol 1993;74(2):211-217. View abstract.
Bach N, Thung SN, Schaffner F. Comfrey herb tea-induced heapatic veno-occlusive disesae. Am J Med 1989;87:97-9. View abstract.
Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. View abstract.
Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market. July 6, 2001. Available at: http://www.cfsan.fda.gov/~dms/dspltr06.html.
Huxtable RJ, Awang DV. Pyrrolizidine poisoning. Am J Med 1990;89:547-8.
Koll R, Klingenburg S. [Therapeutic characteristance and tolerance of topical comfrey preparations. Results of an observational study of patients]. Fortschr Med Orig 2002;120:1-9. View abstract.
Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995;50:83-98.
Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708. View abstract.
Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8. View abstract.
Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. View abstract.
Yeong ML, Swinburn B, Kennedy M, Nicholson G. Hepatic veno-occlusive disease associated with comfrey ingestion. J Gastroenterol Hepatol 1990;5:211-4. View abstract.