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Symphytum officinale
Scientific Name: Comfrey
Other Names: Ass Ear, Black Root, Blackwort, Bruisewort, Common Comfrey, Consolidae Radix, Consound, Gum Plant, Healing Herb, Knitback, Knitbone, Salsify, Slippery Root, Symphytum Radix, Wallwort
Be very cautious using this plant as herbal remedy
Comfrey contains chemicals that are unsafe to take by mouth. Some of these chemicals, known as pyrrolizidine alkaloids, have been associated with liver damage in humans. Some study animal that were given comfrey developed liver cancer.
In 2001, the U.S. Food and Drug Administration (FDA) and the U.S. Federal Trade Commission (FTC) asked manufacturers to remove all oral comfrey products from the U.S. market. Oral forms of comfrey are also prohibited in several other countries, but they may be sold in some places if they are labeled as a dietary supplement. Warnings were also placed on the labels of topical products that contain comfrey. As recently as December 2003, the Canadian health organization, Health Canada, re-issued warnings that comfrey products may contain harmful chemicals and that comfrey should neither be taken orally nor be applied to raw skin.
Not all pyrrolizidine alkaloids are poisonous to humans, but the kinds, amounts, and proportions of pyrrolizidine alkaloids in comfrey products may vary greatly. Which type of comfrey plants were used, where they grew, what the weather conditions were, what time of year they were harvested, how they are processed, and where they were stored, all may affect the composition of commercial comfrey products.
The damage may be gradual, so comfrey poisoning may not be evident for periods up to 3 months.
Especially when high doses are used, or when low doses have been taken for long periods of time, pyrrolizidine alkaloids have been associated with causing a rare, but severe condition known as hepatic veno-occlusive disease. In this condition, the blood veins in the liver become clogged because a liver enzyme changes pyrrolizidine alkaloids into chemicals that may stick to the inside of veins and damage vein tissue. They may also damage lung tissue, potentially resulting in pulmonary hypertension, which is high blood pressure in the artery from the heart to the lungs. Some of the chemicals produced when pyrrolizidine alkaloids break down may stay in the body for years, continuing to damage blood vessels or other tissue.
However, comfrey contains several potentially beneficial substances that may be applied to the skin. Generally, it has high concentrations of allantoin, a protein that encourages new cells to grow; rosmarinic acid, which is known to be anti-inflammatory; and tannins, that help to firm skin tone. It may also have pain-relieving effects. Because comfrey also contains mucilage, which swells in liquids, it forms a soft, sticky covering that stays in contact with the skin. All of these properties make comfrey useful when applied topically to soothe and treat arthritis pain, bruises, minor skin irritation, and sprains. It should be used only on small places of unbroken skin, however--not on large areas or open wounds. A mouth rinse made from comfrey may have some benefit in soothing sore gums and sore throat, but care must be taken not to swallow it. The mouth should be rinsed thoroughly with plain water after a comfrey rinse has been used. |
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