Pennyroyal (Mentha pulegium) is a plant in the Lamiaceae family; its oil is used to make medicine and in manufacturing, pennyroyal oil is used as a dog and cat flea repellent; and as a fragrance for detergents, perfumes, and soaps. Pennyroyal was traditional used as a folk remedy and culinary herb, its oil is also used in aromatherapy, but it is said to be poisonous because it contains high amount of pulegone, a very toxic compound which can affect the liver and uterine function and as such should never be taken internally, even in small doses, consumption of the oil can be fatal.
Pennyroyal oil is extracted by steam distillation from the leaves of the plant; there have been many reported cases of pennyroyal oil toxicity, usually arising within a few hours of ingestion. Cardiovascular collapse with disseminated intravascular coagulation is the usual presentation, but some people develop acute liver injury with marked elevations in serum aminotransferase levels and early signs of liver failure, such as prolongation of the prothrombin time and hepatic encephalopathy.
Pennyroyal oil was commonly used to terminate unplanned pregnancies by many women but there are lots of reported cases of liver failure and even death when used. Even though it aborted the pregnancy it killed the mother as well. In fact, the National Institute of Health recommends avoiding all medicinal uses of pennyroyal oil, since it can cause liver damage even when absorbed through the skin and should instead use another alternative. Small amounts of pennyroyal oil may be used externally (on the skin). Pennyroyal oil is highly concentrated and only a few drops should be used since it tends to be irritating to the skin, it is capable of causing dermatitis and in severe cases blisters or necrotic wounds.
In the end pennyroyal oil should not be used, consult poison control centre or an emergency room immediately if accidentally consumed. Do not use during pregnancy or if breastfeeding.