RESUMEN
Most plant bearing pyrrolizidine alkaloids (PAs) are toxic to men and animals. These natural products are recognized to be hepatotoxic, pneumotoxic, carcinogenic and mutagenic. Thus, the presence of toxic pyrrolizidine alkaloids in certain medicinal plants entails a serious health risk. Moreover, people are exposed to undetermined toxicity hazards of pyrrolizidine alkaloid-containing plants due to the consumption of milk and meat from chronically PA-poisoned animals and honey from wild bees. Symphytum officinale (comfrey) has been used freely as tea, topical cream, salad and beverage. This is a clear and actual example of how lack of knowledge about chemistry and toxicology of a plant made easy its spreading in the consumer society as beneficial and safe.