Allantoin, which is good for healing wounds, is a key active ingredient in the roots and leaves of comfrey. Comfrey herb and leaf also contain rosmarinic acid, which helps decrease inflammation and helps heal blood-vessel injuries in the lungs. Plant Description Comfrey is a herbaceous perennial that originated in Europe and temperate parts of Asia. Comfrey products are made from the leaves or other parts of the plant grown above the ground. They can also be made from the roots, but root preparations are more likely to cause poisoning.
Comfrey contains allantoin, rosmarinic acid, and pyrrolizidine-type alkaloids.
Some think that comfrey is a beneficial herb, but scientific studies show that this herb can be very toxic. If you drink comfrey preparations or take it internally in other forms you run the risk of being poisoned. Some people have even died from eating or drinking comfrey remedies. Echimidine is the most poisonous pyrrolizidine alkaloid found in comfrey. The roots of all comfrey plants contain 10 times as much poisonous compound as the leaves.