What You Need to Know About Pennyroyal

Image Gallery When properly used, the leaves of the pennyroyal plant (Mentha pulegium) can safely deter fleas and insects. WIL MEINDERTS/FOTONATURA.COM

For 35 years, the writers and readers of Mother Earth News have shared hundreds of ways to use herbs to make life more enjoyable. In our archived articles, European and American pennyroyal (Mentha pulegium and Hedeoma pulegiodes) have been recommended as a way to deter fleas, as a vapor to relieve nasal congestion caused by colds, and as an infusion to cleanse the body of toxins.

We stand by using the pennyroyal plant to deter pests, but new information on the active ingredient in both species of pennyroyal, pulegone, merits a recall of taking pennyroyal into your body. In 1996, two California infants died after being given mint tea, in which the mint turned out to be pennyroyal. Most other pennyroyal incidents involve the use of pennyroyal essential oil (generally used for therapeutic or homeopathic purposes or as an insect repellent), which is so potent that it should be considered a poison. In the interest of safety, never use pennyroyal essential oil for anything, not ever.

Two thousand years ago, pennyroyal was the herb used to terminate unwanted pregnancies. Dr. Art Tucker, research professor at Delaware State University and author of The Big Book of Herbs, says that pennyroyal induces abortions by first damaging the mother's liver. Death sometimes follows. In a well-documented case from 1994, a college student who drank only 2 teaspoons of pennyroyal oil in teas over a two-day period died from it. In 1992, a healthy dog died after licking a similar amount from its fur.