Herbs & Supplements

Should I take it?

Believed to have originated in Asia and Europe, comfrey now thrives in most temperate climates throughout the world. At various times in history, it has been cultivated, but currently it most often grows wild in marshy areas or grassy meadows. A shrubby perennial plant that can reach 2 feet to 5 feet in height, it can be a nuisance--choking out crops and ornamental plants, if it is not controlled. Comfrey has thick, fuzzy stems, long lower leaves, and purple or blue bell-shaped flowers that bloom during the summer months. In some parts of the world, comfrey leaves were eaten as a vegetable, the roots were dried and roasted for a coffee substitute, and animal feed was made from the whole plant. Its use as food is largely outdated, however. In the summer of 2001, the FDA required the manufacturers of oral dietary supplements for humans to stop including comfrey in products sold in the U.S. Since then, comfrey has also been removed from commercial animal feeds.

The leaves, rhizomes, and roots of comfrey have all been used in medicine. Rhizomes are fleshy extensions of plant stems that run along or under the ground and often produce shoots and roots for new plants. Until the 1960s when their pyrrolizidine alkaloid content was discovered, oral forms of comfrey were taken to treat digestive and respiratory conditions. More effective and safer oral products are now on the market. Although oral forms of comfrey still may be available in the United States and other countries, taking comfrey by mouth is not recommended due to rare but severe side effects potentially caused by pyrrolizidine alkaloids it may contain. In general, the underground parts of comfrey (roots and rhizomes) contain much more of the pyrrolizidine alkaloids than the leaves; and the small, new leaves have more than larger, older leaves. Comfrey may be added to creams, gels, salves, or ointments to treat conditions such as acne and psoriasis, as long as the skin is not raw or scratched. It is also included in soaps, cosmetics, dry skin lotions, and lip balms.

Dosage and Administration

Due to the possibility that it may cause liver damage, comfrey is not recommended for oral use.

Topical preparations, such as chapped-lip ointments, that include comfrey usually contain between 5% and 20% of an extract made from the leaves or roots of comfrey. The pyrrolizidine alkaloids that make comfrey unsuitable for oral use are also absorbed through the skin, but how much is absorbed is not known. Therefore, only small amounts of comfrey-containing products should be applied per day for a maximum of 10 days at a time. The use of topical comfrey preparations should be limited to a total of 6 weeks or less per year. Individuals who appear to have reactions should stop using comfrey and see a doctor as soon as possible.

Summary

Applied to unbroken skin, comfrey can help relieve inflammation and soreness caused by arthritis or soft tissue injuries such as bruises and by minor skin irritation such as razor burn. It should not be applied to cut or broken skin and it should not be taken orally.

Risks

When taken by mouth, comfrey has been reported to cause liver damage--including liver cancer in animals and rare cases of veno-occlusive disease (obstructed blood vessels in the liver or lungs) in humans. While comfrey poisoning is extremely rare, it is also unpredictable, affecting some apparently healthy individuals at small doses. Comfrey should never be taken orally.

When comfrey products are applied to the skin, variable amounts of pyrrolizidine alkaloids may be absorbed into the body. Topical comfrey should be used in small amounts for a maximum of 10 days at a time for a total annual use of 6 weeks or less. Pregnant and breast-feeding women, children, the elderly, individuals with chronic illnesses, and individuals with known or suspected alcoholism or liver diseases should avoid using it.

Side Effects

When applied to the skin for long periods or in high amounts, comfrey may be associated with abdominal pain, loss of appetite, and tiredness. Handling the leaves of the comfrey plant may result in skin irritation of the hands.

Interactions

Reportedly, phenobarbital may accelerate and/or increase the formation of toxic chemicals from comfrey under laboratory conditions. If comfrey is used at the same time as other herbals, such as kava and valerian, that could cause liver damage, the risk of liver damage may increase.

Last Revised July 18, 2008