Pyrrolizidine alkaloid herbs (comfrey/borage/coltsfoot)

Tier 4 — risky / avoid · Liver veno-occlusive disease · Carcinogen · Cumulative toxicity

Pyrrolizidine alkaloids (PAs) found in comfrey, borage, coltsfoot, butterbur (unpurified), and other herbs cause hepatic veno-occlusive disease — blood vessels in the liver become blocked, leading to liver failure. PAs are also confirmed genotoxic carcinogens. Toxicity is cumulative — damage accumulates silently over months before sudden liver failure. EFSA sets the margin of exposure as unacceptable at any intake level.

Dose: NO safe intake level — EFSA considers any PA exposure an unacceptable cancer risk; cumulative hepatotoxicity