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Comfrey

Comfrey is also known as common comfrey, comfrey root and comfrey root. Although this plant contains toxic chemicals known as pyrrolizidine alkaloids, the leaves, root and root stem are used to make medicine. The amount of pyrrolizidine alkaloids found in comfrey varies depending on the harvest time and age of the plant. The root contains ten times more pyrrolizidine alkaloids than the leaves. Some products sold as true comfrey (Symphytum officinale) contain more toxic rough comfrey (Symphytum asperum) or fodder comfrey (Symphytum uplandicum). Comfrey is used as a tea for stomach complaints, stomach ulcers, heavy menstrual periods, diarrhea, bloody urine, persistent coughs, pain when breathing, bronchitis, cancer and chest pain. It is also used as a gargle solution for gum disease and sore throats. Comfrey is applied to the skin for skin ulcers, wounds, inflamed joints, bruises, rheumatoid arthritis, swollen veins, gout and broken bones.

How does comfrey work?

The chemicals contained in comfrey may have a healing effect and reduce inflammation when applied to the skin. However, comfrey also contains toxic chemicals that can be absorbed through the skin.

How effective is comfrey?

There is not enough scientific data to make a statement about the effectiveness of comfrey applied to the skin for bruises and sprains. New research suggests that applying comfrey to the skin may relieve pain and tension from bruises and sprains, as well as pain around muscles and joints. There is also insufficient scientific data on the effectiveness of comfrey for skin ulcers, wounds, broken bones, heavy menstrual periods, diarrhea, coughs, sore throats, gum disease, joint pain, breast pain, cancer and inflammation. Further scientific research is needed to evaluate the effectiveness of comfrey in these applications.

Safety and side effects

Comfrey is probably not safe and harmless when taken orally. It contains chemicals known as pyrrolizidine alkaloids, which can cause liver damage, lung damage and cancer.

Comfrey appears to be safe and harmless for most people when applied in small amounts to uninjured skin for less than 10 days. It is important to remember that the toxic chemicals in comfrey can be absorbed through the skin. Absorption of these chemicals increases when the skin is injured or large amounts of comfrey are applied.

Precautions and warnings

Pregnancy and breastfeeding: Comfrey taken orally or applied to the skin is unlikely to be safe for pregnant or breastfeeding women. In addition to the fact that the pyrrolizidine alkaloids in comfrey can cause liver damage and cancer, these chemicals can also cause birth defects. Even use on the skin should be avoided, as the pyrrolizidine alkaloids it contains can be absorbed through the skin.

Injured or damaged skin: Comfrey should not be applied to injured or damaged skin, as the toxic pyrrolizidine alkaloids it contains are absorbed in larger quantities on injured or damaged skin and could cause liver damage and other serious side effects.

Liver disorders: There are concerns that comfrey may exacerbate liver damage, so people suffering from liver problems should avoid comfrey products.

Interactions

Comfrey should not be used in combination with the following medications:

Medications that can damage the liver

Comfrey could damage the liver. The use of comfrey in combination with medicines that can also damage the liver can increase the risk of liver damage. For this reason, comfrey should not be used if you are taking medication that can damage the liver.

Care should be taken when combining comfrey with the following medications:

Medications that accelerate the breakdown of other medications by the liver

Comfrey is broken down by the liver. Some chemicals produced when comfrey is broken down by the liver can be harmful. Medications that accelerate the breakdown of comfrey by the liver may increase the toxic effects of comfrey breakdown products.

Dosage

An appropriate dosage of comfrey depends on various factors such as age, state of health and others. At this time, there is insufficient scientific data to determine appropriate dosage ranges for comfrey. For this reason, you should follow the dosage instructions on the label and/or consult a doctor or pharmacist before use.

References

  1. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46.
  2. 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.
  3. Huxtable RJ, Awang DV. Pyrrolizidine poisoning. Am J Med 1990;89:547-8.
  4. 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.
  5. Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmacy 1995;50:83-98.
  6. Stewart MJ, Steenkamp V. Pyrrolizidine poisoning: a neglected area in human toxicology. Ther Drug Monit 2001;23:698-708.
  7. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8.
  8. 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.