Comfrey is a powerful healing plant that is sometimes called the king of the vulneraries (healing plants). Unfortunately, comfrey bears a stigma. In the 1970s, scientists discovered the presence of pyrrolizidine alkaloids (PAs) in comfrey that could harm the liver. Panic spreads much faster than prudence or careful research, and soon comfrey had fallen out of favor. The medical community turned against comfrey. Some countries even banned its sale. Read more.