Symphytum officinale -- Comfrey
Symphytum officinale, more commonly known as comfrey, belongs to the family Boraginaceae. Comfrey is a common wild plant in parts of the U.S. and is cultivated in much of the world. It is a perennial herb with deep roots. Comfrey has large, rough, prickly leaves and pinkish or creamy bell-like flowers. When it is not flowering, it is often confused with foxglove (Digitalis spp.). Comfrey is commonly used to make tea. It also has been promoted in the past as a forage crop.
There seems to be a great deal of difference in opinion regarding the medicinal use of comfrey. In some sources used for this web page, the medicinal use of comfrey is highly criticized. In fact, it has been banned from sale in some countries such as Canada. However, in another source used for this web page, comfrey was promoted as a great medicinal plant and people were advised to ignore the findings of scientists.
Comfrey contains at least eight pyrrolizidine alkaloids (PA). The amount of PAs in roots ranges from 0.3-0.4%. The content in leaves usually is lower. (For more information regarding the compounds in comfrey refer to USDA Phytochemical and Ethnobotanical Databases).
Some of the compounds in Comfrey are:
There are several dangers associated with the use of comfrey. One of the biggest problems is that people accidentally collect foxglove instead of comfrey. Foxglove is deadly. Among other things, it can cause irregular heart beats and convulsions.
Another problem with comfrey is that it contains at least eight pyrrolizidine alkaloids (PA). While the level of PAs in fresh plant may not be very high, ready-to-use preparation often have high levels (e.g., 270-2900 mg/kg). PAs are hepatoxins and can cause irreversible liver damage. One of the problems is that the effects of the alkaloids can be cumulative. Therefore, damage to the liver may not be associated to the alkaloids in comfrey. Sometimes toxicity signs will not be present until an animal is stressed by something that requires greater liver function (e.g., lactation). Also, the leaves and roots of comfrey have been shown to be carcinogenic. PAs from comfrey given to rats caused mortality. Liver pathology was characteristic of PA toxicosis. When rats were fed dietary levels of 0.5% roots and 8% leaves, they formed hepatomas.
There are species differences in susceptibility to PAs. Horses and cattle are most commonly poisoned by PAs, while sheep are much more resistant. Goats are more susceptible than sheep, and pigs are more susceptible than cattle and horses. Common clinical signs from PA toxicity include: jaundiced skin (from impaired liver function); rough unkempt appearance; diarrhea; prolapsed rectum; edema of tissues of the digestive tract; dullness; photosensitization; and abnormal behaviour. Horses may have neurological signs such as "head pressing." Poisoned cattle may have a bloated appearance. Further information on PAs and species differences is presented in Cheeke 1998.
Comfrey has been promoted and used as a medicinal plant for years. However, no published studies could be found to support the medicinal claims.
In the Philippines, the leaves are made into a decoction and used as a drench for swine to treat fevers. One half to one cup of the decoction is given to the swine 3 times a day for 2-3 days. It also is recommended as a treatment for dogs after hip dysplasia. The dose is one tablespoon of minced leaves or three comfrey tablets twice a day, five days a week until the problem is gone. Some other oral uses of comfrey in dogs include treating rickets, arthritis, and rheumatism. For livestock, it is recommended as a treatment for internal hemorrhaging, ulcers, arthritis, broken bones, and rheumatism. Preparation consists of boiling one pound of comfrey in 1.5 quarts of water for one hour. Ground-ivy and Spanish liquorice can be added. A half pint drench is given to the animal three times/day. Molasses is supposed to be added to the mixture when the treatment is for ulcers. The dose for treating broken bones in livestock is two handfuls of well bruised roots/day.
Comfrey leaves and roots also are used topically to treat wounds, arthritis, sprains, and broken bones. In these applications, allantoin is believed to be the effective compound. Absorption of PAs through the skin, based on tests with rats, is 20-50 times lower than when orally administered, thus decreasing the toxic risks.
Some Uses in Humans:
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