Pennyroyal is an extremely toxic herb that has caused multiorgan failure and death in several people.
Pennyroyal is a flowering plant that was used in folk medicine to induce abortion, alleviate menstrual symptoms, and to treat inflammatory conditions and minor ailments. The oil itself is highly toxic, and is not recommended for internal use. A substance called pugelone in pennyroyal is thought to be responsible for its toxic effects and tissue damage. Studies in both animals and humans show that pulegone is also directly toxic to the nervous system. There have been a number of case reports and also several deaths attributed to the use of this botanical.