Parts Used & Where Grown
Two similar plants go by the name pennyroyal, one native to Europe (and therefore called European pennyroyal) and one native to North America (and therefore called American pennyroyal). Both are members of the mint family (Lamiaceae) and grow in temperate regions of Europe and the Americas. The flowering tops are used as medicine, but the internal use of the volatile oil should be strictly avoided.
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3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
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1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
This supplement has been used in connection with the following health conditions:
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Pennyroyal is one of a group of “nerve tonic” (nervine) herbs used in traditional herbal medicine for people with anxiety, with few reports of toxicity.
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Pennyroyal has a long history of use for relieving coughs.
The mucilage of Reference slippery elm gives it a soothing effect for coughs. Reference Usnea also contains mucilage, which may be helpful in easing irritating coughs. There is a long tradition of using Reference wild cherry syrups to treat coughs. Other traditional remedies to relieve coughs include Reference bloodroot, Reference catnip, Reference comfrey (the above-ground parts, not the root), Reference horehound, Reference elecampane, Reference mullein, Reference lobelia, Reference hyssop, Reference licorice, Reference mallow, (Malvia sylvestris), Reference red clover, Reference ivy leaf, Reference pennyroyal (Hedeoma pulegioides, Mentha pulegium), Reference onion, (Allium cepa), and Reference plantain (Plantago lanceolata, P. major). None of these has been investigated in human trials, so their true efficacy for relieving coughs is unknown.
Traditional Use (May Not Be Supported by Scientific Studies)
Since the time of the ancient Greeks, pennyroyal was considered a useful insect repellant, reflected in modern times by the common name fleabane.1 The Latin names of both plants also reflect this insect-repelling power—pulegoides and pulegium both derive from the Latin word for flea. It was also believed to stimulate menstruation. Various folk herb traditions have employed American or European pennyroyal to help relieve Reference coughs, Reference upset stomachs, and Reference anxiety.2
How It Works
How It Works
Like all mint family plants, pennyroyal owes much of its medicinal activity to the presence of a volatile oil. The primary component of this oil is known as pulegone. Pulegone is converted to menthofuran by the body. If large enough amounts of pulegone are consumed, the amount of menthofuran produced can seriously damage the liver and nervous system.3 Smaller amounts of the volatile oil contained in the whole plant appear to have mild, smooth, muscle-relaxing effects that might help explain the historical use of pennyroyal for Reference indigestion, stomach cramps, and Reference cough.4 No modern clinical trials have been completed to support these indications, and other herbs with soothing effects on the gastrointestinal tract, such as Reference chamomile and Reference peppermint, have a much greater history of safety than pennyroyal.
How to Use It
For adults (excluding Reference pregnant or nursing women, children, and people with liver or kidney disease), a tea of pennyroyal can be prepared by putting 1–2 teaspoons (5–10 grams) of the herb in 1 cup (250 ml) of boiling water and allowing it to steep for 10–15 minutes.5 Up to 2 cups (500 ml) per day can be drunk. Pennyroyal tincture can be mixed with a skin cream and applied topically to repel insects, though it is unknown whether this is effective due to a lack of scientific study. The tincture and volatile oil are not recommended for internal use.
Interactions with Supplements, Foods, & Other Compounds
Interactions with Medicines
Used internally in the recommended amounts, pennyroyal is generally safe, though an occasional person may experience intestinal upset or temporary dizziness.6 Pulegone and its toxic metabolites, particularly menthofuran, damage the liver and nerves if taken in sufficiently large quantities.7 If used during Reference pregnancy, pennyroyal may cause fetal death by liver and brain damage as well as promote uterine contractions to expel the fetus.8 Therefore pregnant or nursing women should absolutely avoid pennyroyal in any form. The traditional use of the herb to induce an abortion has led to many reports of nervous system toxicity in pregnant women. Internal ingestion of pennyroyal volatile oil should be avoided by everyone. People with liver failure or kidney failure, and all children, should avoid pennyroyal. Signs and symptoms of pennyroyal toxicity include severe stomach pain, dizziness, seizures, vomiting, difficulty walking, and coma. Since 1905, 18 cases of injury (with complete recovery in every case) and four deaths related to pennyroyal have been reported in the medical literature.9 The majority of acute poisonings and deaths reported with pennyroyal have been in cases of women using the oil attempting to induce an abortion.
1. Castleman M. The Healing Herbs: The Ultimate Guide to the Curative Power of Nature’s Medicines. New York: Bantam Books, 1991, 417–22.
2. Castleman M. The Healing Herbs: The Ultimate Guide to the Curative Power of Nature’s Medicines. New York: Bantam Books, 1991, 417–22.
3. Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996;124:726–34.
4. Castleman M. The Healing Herbs: The Ultimate Guide to the Curative Power of Nature’s Medicines. New York: Bantam Books, 1991, 417–22.
5. Castleman M. The Healing Herbs: The Ultimate Guide to the Curative Power of Nature’s Medicines. New York: Bantam Books, 1991, 417–22.
6. Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996;124:726–34.
7. Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996;124:726–34.
8. Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996;124:726–34.
9. Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996;124:726–34.
Last Review: 11-07-2012
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2013.