What are the side effects of comfrey?

What are the possible side effects of comfrey ()? Although rare, allergic reactions to comfrey may occur. Stop using comfrey and seek emergency medical attention if you experience symptoms of a serious allergic reaction including difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives.Comfrey has been associated with cases of severe liver damage. Notify your doctor immediately if you develop nausea, vomiting, abdominal pain, unusual fatigue, loss of appetite, yellow skin or eyes, itching, dark urine, or clay colored stools. These symptoms may be early signs of liver damage.This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Source: