encyclopedia

Comfrey

Scientific Names:    

Symphytum officinale L. [Fam. Boraginaceae]    
     

Forms:    

Dried and cut root and leaf of comfrey; comfrey root extracts; allantoin creams.    
     

Traditional Usage:    

– Bone and Joint Conditions
– Breast Tenderness (leaf compress)
– Bruises
– Compress
– Fractures
– Gum disease
– Inflammation
– Joint Dislocations
– Skin Problems
– Sore throat
– Sprains
– Swelling (topically)
– Tissue Damage     
 
     
Overview:    

Comfrey, Symphytum officinale L. [Fam. Boraginaceae], also known as boneset and knitbone, originated in Europe but is now naturalized in North America, growing mainly in moist and grassy environments. Traditionally it was used to treat conditions ranging from bruises and sprains to pulmonary, gastric and renal difficulties. The name comfrey comes from the Latin “con firma” which means grow together. It was used as a folk remedy for healing bone fractures; a claim that has been confirmed scientifically, as comfrey contains allantoin, a compound known to help promote the formation of new tissue. Comfrey is also known to diminish swelling and inflammation. Comfrey root is a controversial drug and has been banned for internal use or restricted in many parts of the world such as Australia, Canada, New Zealand, and in the UK. Much of the controversy surrounding comfrey is owing to studies in rats that have shown the pyrrolizidine alkaloids present in the drug are hepatotoxic, carcinogenic and mutagenic and therefore could be potentially harmful to humans. There have been at least four documented cases of death from comfrey over-use and some recommend that the root and leaf should no longer be taken internally. Others claim that there are more carcinogens in a can of popular cola drinks than there are in a cup of comfrey leaf tea. However, recent studies claim that there is significant risk of liver toxicity from the leaf tea as well. The toxicity may be partly explained by recently discovered toxic quinoids that form dangerous DNA adducts within the body from extracts of comfrey, sassafras and rosemary, all plants that are known to contain compounds that are either carcinogenic or toxic to mammals. As expected, no adducts of reactive metabolites were found in extracts of red clover and other herbs known to be safe.    
     
    
Active Ingredients:    

Comfrey root contains: 0.6-0.8% allantoin; 0.02-0.07% pyrrolizidine alkaloids: intermedine, acetylintermedine, lycopsamine, acetyllycopsamine, symphytine, and in materials from some sources also echimidine, all these also being partly present a N-oxides; 4-6% tannins; abundant mucilage (fructans); starch; triterpenes (isobauerenol) and sterols (sitosterol); depsides of dehydrocaffeic acid (=”lithospermic acid”); 1-3% asparagine; amino acids (including y-aminobutyric acid). Comfrey leaf contains: Approximately 1.3% allantoin; carotenes; rosmarinic acid; ca. 4.0% silicic acid; symlandine; ca. 8.0-9.0% tannin; viridiflorine. Duke (1985) reports that comfrey also contains many vitamins including (per 100g): ca. 0.5mg thiamine; ca. 1mg riboflavin; ca. 5mg nicotinic acid; ca. 4.2mg pantothenic acid; ca. 0.07mg vitamin B12; 28,000 IU vitamin A; 100mg vitamin C; 30 mg vitamin E and 0.18mg allantoin; and other ubiquitous compounds.    
     
    
Suggested Amount:    

Tea: Pour boiling water over 5-10 grams of finely chopped or powered comfrey leaf. Steep 10-15 minutes then strain. Drink one cup two or three times a day but not for a prolonged period. External: Use as a poultice or compress with a 1:10 decoction; leaf compresses can also be made. 1 teaspoon = 4 grams.
 

Warning:

The drug should only be applied to the intact skin.
Use sparingly. Do not use for longer than 4 to 6 weeks in a year.
    
  
Drug Interactions:    

None known.    
   
     
Contraindications:    

Do not use if you are pregnant or breastfeeding.    
     
    
Side Effects:    

Internal use not recommended.
Overdose of drug can damage the liver.
Pyrrolizidine alkaloids have carcinogenic properties; avoid over-use.     
     
    
References:    

Bach N, Thung SN, Schaffner F. 1989. Comfrey herb tea-induced hepatic veno-occlusive disease. Am J Med. 1989 Jul; 87(1): 97-9.
 
Duke JA. 1985. Symphytum peregrinum Ledeb. (Boraginaceae). In Handbook of Medicinal Herbs. CRC Press, Boca Raton, FL, p. 464-466.
 
Johnson BM, Bolton JL, van Breemen RB. 2001. Screening botanical extracts for quinoid metabolites. Chem Res Toxicol. 2001 Nov; 14(11): 1546-51.
 
Stickel F, Seitz HK. 2000. The efficacy and safety of comfrey. Public Health Nutr. 2000 Dec; 3(4A): 501-8. Review.
 
Wichtl M (ed). 1994. Symphyti radix – Comfrey root. In Herbal Drugs and Phyto-pharmaceuticals. (English translation by Norman Grainger Bisset). CRC Press, Stuttgart.