Pennyroyal is an herb -- part of the mint family (Mentha pulgium) -- and the oil or extract from its leaves has been used throughout human history as an insect and flea repellent, a fragrance (in perfumes and in aromatherapies), as well as a food flavoring. Pennyroyal tea has also been used as a contraceptive, although it wasn't really used to prevent pregnancy; rather, it was more likely women used it as a tea after the fact, to attempt abortion. Did it work? A naturally-occurring plant compound called pulegone found in pennyroyal is now known to be toxic, and can cause seizures, induce a coma, cause liver and cardiovascular failure, and can injure multiple organs (and quickly, too). Sure, it may also stimulate the uterus to induce menstruation and terminate a pregnancy, but it may also kill you in the process.