Comfrey Root Side Effects

Herbalists around the world recommend the application of comfrey root as a first aid measure because of its many healing properties. However, scientific research links comfrey root to liver damage and liver cancer. Comfrey root has a long list of possible side effects and interacts negatively with many commonly prescribed medications.

How It Works

Comfrey root contains allantoin, a compound which, when applied to a wound, causes the skin to contract and close in less time. This reduces the chance of infection and curtails scarring. Allantoin destroys red blood cells, which explains how it assists with healing bruises and other injuries involving damaged blood vessels.

Comfrey Root Uses

Comfrey root has been used as a first aid remedy in China for more than 2,000 years to relieve pain, encourage healing of broken bones, decrease swelling, and repair tissue. Scientific studies performed since the early 1990's support the claims of the comfrey root's healing properties. It is recommended by herbalists for the treatment of pain, myalgia, inflammation, tendinitis, arthritis, bruises and other contusions, and swelling.

Side Effects

Comfrey root has been found to interact negatively with certain cholesterol-lowering medications, medications used in chemotherapy, male hormone replacement, and some drugs prescribed to heal infections. Drug interactions have occurred with methotrexate (for example, Folex and Rheumatrex) and valproic acid (for example Depacon, Depakene, and Depakote). Allergic reactions to comfrey root are reportedly rare. However, symptoms of an allergic reaction may include tightness in the throat and chest, trouble breathing, chest pain, and reactions of the skin, such as hives, itching, or swelling. If you experience any of these symptoms while using comfrey root, contact your physician.


There are no there are no regulated manufacturing standards for products containing comfrey root. Pyrrolizidine alkaloids are present in comfrey root and the leaves of the plant, but a greater concentration exists in the roots than in the leaves. Comfrey root is sold in the forms of extracts, ointments, tea, and powder. However, because the heavy concentration of pyrrolizidine alkaloids have been scientifically proven to cause severe liver damage, oral use of the plant is discouraged, even by most herbalists. Early symptoms of liver problems include stomach pain, jaundice, nausea or vomiting, extreme fatigue, loss of appetite, itchy skin, and/or unusual colored urine or stools. Contact your doctor immediately if you experience any of these indicators while using comfrey root. Comfrey root should not be used in any form if you are pregnant. If you are nursing, the toxins in the root may be emitted through breast milk.

Keywords: comfrey root, medicinal herbs, liver problems

About this Author

Susan Steen graduated from the University of New Orleans, where she earned a B.A. in sociology and a certification in social work. She has been a freelance and contract writer for 22 years. Her work has been published in “Evidence Technology Magazine,” “Louisiana Bar Journal,” the Cobblestone children’s educational publications “Faces” and “Appleseeds,” the Waterford Literacy Program, and a variety of websites.