Comfrey Leaf & Root, Cautions

• The presence of liver toxic substances in comfrey have raised doubts over the safety of the herb when taken internally. These are likely to prove ill-founded but it is better to be on the safe side and avoid taking the root internally and avoiding excessive use of the leaves internally.
• Do not use on open, unclean wound or very deep wounds as fast healing can mean that dirt and bacteria are trapped inside.
• On July 6, 2001 the U.S. Food and Drug Administration, along with the Center for Food Safety and Applied Nutrition,advised all dietary supplement manufacturers to remove products containing comfrey from the market.
• Comfrey contains unsaturated pyrrolizidine alkaloids, which are hepatotoxic and hepatocarcinogenic.

Contraindications & Interactions (PA-Containing Herb Framework)

Common comfrey (Symphytum officinale) contains hepatotoxic pyrrolizidine alkaloids (PAs). See also: Pyrrolizidine and Quinolizidine Alkaloids.

Internal Use

Internal use of comfrey leaf or root is broadly discouraged in modern practice due to PA-related liver toxicity risk. If used at all, it should be:

• Restricted to very short-term, situation-specific internal use
• At lowest effective doses
• Avoided in combination with other PA-containing plants

Topical Use

• Topical use (ointments, salves, poultices) still has a role, especially for musculoskeletal injuries and wound-healing, but prolonged or very large-area application may still contribute some systemic exposure.

Contraindications / Strong Cautions (Internal, and Cautious with Extensive Topical Use)

• Known or suspected liver disease (hepatitis, cirrhosis, significant NAFLD, unexplained elevated LFTs)
• Pregnancy and lactation
• Infants and young children (internal use)
• History of unexplained hepatic reactions to herbs or drugs
• Concurrent use of other PA-containing herbs

Potential Interactions (Conceptual, PA Framework)

• Additive risk with hepatotoxic medications
• Increased hepatic burden when combined with multiple liver-metabolized drugs and herbs
• Avoid stacking multiple PA sources simultaneously

PA Status: Contains 1,2-unsaturated PAs — internal use broadly discouraged; topical preferred, watching area and duration. See Pyrrolizidine and Quinolizidine Alkaloids.

 Hepatotoxicity due to comfrey herb tea. Am J Med 1989;87:701.

 Comfrey herb tea and hepatic veno-occlusive disease. Lancet1989;1:657-8.

 Hepatic veno-occlusive disease associated with the consumption of pyrrolizidine-containing dietary supplements. Gastroenterology 1985;88:1050-4.

 Hepatic veno-occlusive disease associated with comfrey ingestion. J Gastroenterol Hepatol 1990;5:211-4.

Veno-occlusive disease of the liver secondary to ingestion of comfrey. Br Med J 1987;295:183.

 Comfrey and liver damage (letter). Lancet 1981;1:944.