Pennyroyal
Mentha pulegium
The smallest of the mints. The one with the most to answer for.
Overview
Pennyroyal is a small, creeping, intensely aromatic mint of damp, disturbed ground that has been used across the entire sweep of European history as a flea repellent, a digestive herb, a flavouring for black pudding, and — with far more consequence — as an abortifacient. The same essential oil that repels insects, a compound called pulegone, is toxic to the liver and kidneys in quantity, and the history of pennyroyal is inseparable from the history of women seeking to end pregnancies: a history that runs from Roman texts through medieval herbals through nineteenth-century patent medicines through twentieth-century emergency rooms. The plant was not subtle about what it did. The tragedy is how often the dose required to work was also the dose that killed.
Botanical Notes
A low, creeping or ascending perennial reaching 10–35cm with small, oval, finely toothed, strongly mint-scented leaves and whorls of small, lilac-pink flowers from July to October. Found on damp, compacted, often grazed ground — pond margins, seasonal floodplains, trampled paths, and wet heathland — throughout Europe and western Asia. Increasingly rare in Britain due to habitat loss. The essential oil contains pulegone (40–90%), a monoterpene ketone with hepatotoxic, nephrotoxic, and abortifacient properties at concentrations achievable from the concentrated oil.
Lore & History
Pliny described pennyroyal as more powerful than a rose garland for clearing the air and recommended it for dizziness. The Roman cookbook of Apicius uses it in several recipes — black pudding, sauces, and mixed seasonings — as a flavouring that also aided digestion. In medieval Britain it was called puliall-royall or pulegium regale, the royal fleabane, and used to stuff mattresses against fleas. The Greek physician Soranus of Ephesus recommended it as an abortifacient in the second century AD. By the nineteenth century it appeared in American patent medicines sold euphemistically as remedies for "delayed menstruation" — a coded description whose meaning was well understood. Its use for this purpose caused documented deaths throughout the twentieth century and continues to cause them.
Warnings
The essential oil is acutely hepatotoxic — cases of fatal liver failure following ingestion of pennyroyal oil are documented. Do not use the essential oil internally under any circumstances. The herb in small culinary quantities is generally considered safe, but avoid any medicinal quantity during pregnancy — pennyroyal is a dangerous emmenagogue and abortifacient. Do not use large amounts of the tea. The oil applied to skin in concentration can cause systemic toxicity through absorption. Keep the essential oil away from children and pets — it is particularly dangerous to cats.