Preparations of comfrey (also known as Symphytum officinale (common comfrey), S. asperum (prickly comfrey), S. X uplandicum (Russian comfrey)), a fast-growing leafy plant, are widely sold in the United States as teas, tablets, capsules, tinctures, medicinal poultices, and lotions. Since 1985, at least seven cases of hepatic veno-occlusive disease
obstruction of blood flow from the liver with potential scarring (cirrhosis)
including one death
, have been associated with the use of commercially available oral comfrey products.
Comfrey, like a number of other plants (e.g., Senecio species), contains pyrrolizidine alkaloids. The toxicity of pyrrolizidine alkaloids to humans is well-documented. Hepatic veno-occlusive disease following ingestion of pyrrolizidine alkaloid-containing products, has been documented repeatedly throughout the world. Hepatic veno-occlusive disease is usually acute and may result in fatal liver failure
. In less severe cases, liver disease
may progress to a subacute form. Even after apparent recovery, chronic liver disease, including cirrhosis, has been noted. Individuals who ingest small amounts of pyrrolizidine alkaloids for a prolonged period may also be at risk for development of hepatic cirrhosis. The diagnosis of pyrrolizidine alkaloid-induced hepatic veno-occlusive disease is complex, and the condition is probably underdiagnosed.
The degree of injury caused by pyrrolizidine alkaloid-containing plants, like comfrey, is probably influenced by such factors as the age of the user, body mass, gender, and hepatic function, as well the total cumulative dose ingested and the type of exposure (i.e., whether exposure was to leaves or roots, infusions or capsules). Infants in general appear to be particularly susceptible to adverse effects of exposure to pyrrolizidine alkaloids; there are reports of infants developing hepatic veno-occlusive disease following acute exposure of less than one week. Transplacental pyrrolizidine poisoning has been suggested by the occurrence of hepatic disease in the newborn infant of a woman who consumed herbal tea during pregnancy.
Although liver damage is the major documented form of injury to humans from pyrrolizidine alkaloid-containing herbals, animal studies suggest that their toxicity is much broader. Animals exposed to pyrrolizidine alkaloids have developed a wide range of pulmonary, kidney
pathologies. Pyrrolizidine alkaloid-containing plants, including comfrey, have also been shown to cause cancer
in laboratory animals.
Four countries (the United Kingdom, Australia, Canada, and Germany) have recently restricted the availability of products containing comfrey, and other countries permit use of comfrey only under a physician's prescription. In December 2003, Health Canada, the federal department responsible for Canada's health care system, issued an advisory warning consumers to not use any product made from comfrey because it may contain an ingredient, echimidine, linked to liver damage.
See your doctor if you have experienced serious health problems after taking a product containing comfrey. In addition, it may be important to contact an attorney
who can help you protect your legal rights. Please keep in mind that there may be time limits within which you must commence suit.
- Other Supplements: Overview
- Digestive Disorders: Overview
- Kidney Failure
- Liver Failure: Overview