Comfrey root tea (internal)

Tier 4 — risky / avoid · PA hepatotoxicity

Comfrey root taken internally contains high concentrations of pyrrolizidine alkaloids that cause veno-occlusive liver disease — small liver veins become blocked. Multiple countries have banned internal comfrey. Even short-term ingestion has caused severe liver damage. Topical use for muscle and joint pain has much lower systemic absorption and better safety data.

Dose: AVOID internal use; pyrrolizidine alkaloids cause irreversible liver damage; external use only is safer