Pennyroyal is a perennial member of the mint family originally native to Asia and Europe but now naturalized throughout the Americas. Because the herb was used by the ancient Romans to flavor pudding, it also became known as pudding grass. Its reputation for naturally repelling insects gave rise to the common name of mosquito plant.
Certain organic compounds responsible for the aromatic properties of the plant also make it unsuitable for internal use. For example, although the compound menthofuran is used in the fragrance industry, it is highly toxic to the liver.
