Scientific Name: Pennyroyal

Who is this for?

Uses

Note: Pennyroyal oil should never be taken by mouth. It contains a component known as pulegone, which may be highly toxic to the liver. Pulegone may also cause pregnant women to miscarry.

Pennyroyal tea and other oral dosage forms may contain very little pulegone, but they are still not recommended for use.

The dried leaves and stems of American pennyroyal (Hedeoma pulegioides) and the related species European pennyroyal (Mentha pulegium) have both been used to relieve stomach conditions such as cramps and gas. They contain tannins and a small percentage of volatile oils, which are the rapidly evaporating chemicals that give plants their characteristic smells and tastes. Tannins act as astringents on the gastrointestinal tract. An astringent shrinks and tightens the top layers of mucous membranes, thereby reducing secretions, relieving irritation, and improving tissue firmness. Conversely, pennyroyal’s volatile oils and other chemicals in it may cause slight stomach irritation, which may in turn relieve gas. Also called essential oils, volatile oils possess the characteristic smell and taste of the plant. They usually evaporate quickly at room temperature.

Precautions

Pennyroyal oil should never be taken by mouth. If it is ingested, pennyroyal oil may poison the liver. It may also cause kidney, lung, or nerve damage. Deaths have been caused by taking as little as 1/2 teaspoon of pennyroyal oil. No cases of poisoning from using pennyroyal topically have been reported, but pennyroyal oil may be absorbed into the body after being applied to the skin.

Infants given pennyroyal have suffered liver damage and at least one infant died after being given pennyroyal tea. Pennyroyal should not be given to children and adults who use it should keep it where children cannot reach it.

Individuals who have kidney, liver, or lung conditions should avoid using pennyroyal products due to the possibility it may worsen those ailments.

What side effects should I watch for?

Major Side Effects

While severe side effects may be more likely to occur with oral pennyroyal oil, taking dried pennyroyal has also caused serious side effects—especially when taken continually for more than a few days at a time. Taking either form of pennyroyal by mouth has been associated with:

• High blood pressure
• Seizures
• Hallucinations
• Nerve damage
• Liver failure
• Kidney failure
• Breathing failure
• Shock
• Death

Less Severe Side Effects

By mouth, pennyroyal may also cause:

• Confusion
• Fainting
• Fever
• Nausea
• Restlessness
• Stomach pain

Applying pennyroyal oil can cause burning, itching, rashes, or redness at the place where it is applied.

What interactions should I watch for?

No interactions have been identified between pennyroyal and drugs, other herbal products, or foods. Because few studies have been done on pennyroyal and due to the potentially toxic nature of its component pulegone, not all of pennyroyals possible interactions are known.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how pennyroyal interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

Pennyroyal plants are believed to be native to both North America and Europe. Several species of pennyroyal are now found in most mild climate areas of the world. Generally, these members of the mint family of plants are smaller than other species of mint and they tend to lie along the ground rather than send their short stems upright like most other mints. Perennials, they spread very easily, with new roots forming at the points where leaf-nodes on the stems touch the ground. The leaves of pennyroyal are light or grayish green in color and the flowers, which bloom in mid-summer, are blue or purple. Pennyroyal has a very strong minty smell and a minty-acidic taste that make it useful in cooking. The oil has long been used as an antiseptic and an insect repellant. For use as a dried herb in medicine or cooking, the stems—including the leaves—are collected before the flowers appear.

Depending on the species, up to about 2% of the “aerial parts” (flowers, leaves, and stems) of the pennyroyal plant consist of volatile oils, primarily pulegone. Volatile oils are also called essential oils. They possess the characteristic smell and taste of the plant and they usually evaporate quickly at room temperature. In most cases, European pennyroyal contains up to three times as much pulegone as American pennyroyal. Oil distilled from pennyroyal may be used topically as a skin antiseptic or as an insect repellant. In fact, some of its common names (mosquito plant, tick weed) suggest that it has the ability to repel insects and other pests. Some commercially available flea-repelling products for pets contain small amounts of pennyroyal oil, but the death of at least one dog has been documented after pure pennyroyal oil was applied extensively to control fleas. Pennyroyal oil may be included in cosmetics, perfumes, and soaps as a fragrance. It is approved in some countries as a food flavoring, but usually only after the pulegone has been removed.

Dosage and Administration

Pennyroyal oil should not be taken orally.

No dosage recommendations for either oral dried pennyroyal leaves or topical pennyroyal oil have been found in the clinical literature. Because pennyroyal tea and other oral forms of pennyroyal contain very little pulegone, they may be safe to take in small amounts. Pennyroyal oil should be used only topically and only very cautiously because it may be absorbed through the skin.

Summary

Pennyroyal leaves and stems may be dried and used to treat mild stomach complaints such as indigestion. Oil of pennyroyal has been used topically to disinfect skin wounds and to repel insects. Since using either form presents the possibility of severe side effects; however, neither can be recommended for use.

Risks

Pennyroyal should not be taken or applied by pregnant women because it is known to cause miscarriage. It has caused death or liver damage in small children. Therefore young children and breast-feeding women should also avoid using pennyroyal. It may worsen kidney, liver, or lung conditions.

Side Effects

The pulegone in pennyroyal has been known to cause:

• Kidney damage
• Liver damage
• Lung damage
• Nerve damage
• Shock
• Death

Pennyroyal can also cause central nervous system effects such as confusion or gastrointestinal effects such as nausea and vomiting.

Interactions

Although no interactions have been identified between pennyroyal and drugs, herbals, or foods; interactions may exist.

Last Revised May 18, 2007

References

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Anon: Pennyroyal. In: DerMarderosian A, Beutler JA, eds. Facts and Comparisons: The Review of Natural Products. St. Louis, MO, Facts and Comparisons. July 1998.

Bakerink JA, Gospe SM Jr, Dimand RJ, Eldridge MW. Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants. Pediatrics. 1996;98(5):944-947.

Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. Journal of Neurology. 1999;246(8):667-670.

Flamini G, Cioni PL, Puleio R, Morelli I, Panizzi L. Antimicrobial activity of the essential oil of Calamintha nepeta and its constituent pulegone against bacteria and fungi. Phytotherapy Research. 1999;13(4):349-351.

Gold J, Cates W Jr. Herbal abortifacients. Journal of the American Medical Association. 1980;243(13):1365-1366.

Gordon WP, Forte AJ, McMurtry RJ, Gal J, Nelson SD. Hepatotoxicity and pulmonary toxicity of pennyroyal oil and its constituent terpenes in the mouse. Toxicology and Applied Pharmacology. 1982;65(3):413-424.

Grieve M. Pennyroyal. In: A Modern Herbal. New York: Dover Publishers, 1971. Available at: http://www.botanical.com/botanical/mgmh/mgmh.html Posted 1995. Accessed October 7, 2003.

Jellin JM, Gregory P, Batz F, Hitchens K, et al, eds. Pharmacist's Letter/Prescriber's Letter. Natural Medicines Comprehensive Database, 3rd Edition. Stockton CA: Therapeutic Research Facility, 2000.

Natural Medicines Comprehensive Database, Online Edition. Pharmacist's Letter/Prescriber's Letter. Stockton CA: Therapeutic Research Facility, 2006. Available at: http://www.pharmacistsletter.com/(S(ulqz3s45omt3ag55um4kj345))/home.aspx?li=1&st=1&cs=&s=ND.

Ortiz de Urbina AV, Martin ML, Montero MJ, Carron R, Sevilla MA, San Roman L. Antihistaminic activity of pulegone on the guinea-pig ileum. Journal of Pharmacy and Pharmacology. 1990;42(4):295-296.

Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: Stonesong Press; 1999.

Rim IS, Jee CH. Acaricidal effects of herb essential oils against Dermatophagoides farinae and D. pteronyssinus (Acari: Pyroglyphidae) and qualitative analysis of a herb Mentha pulegium(pennyroyal). Korean Journal of Parasitology. 2006;44(2):133-138.

Sievers AF. American pennyroyal. In: Sievers AF. The Herb Hunter's Guide. Misc. Pub. No. 77. Washington D.C. U.S. Department of Agriculture.1930.

Simon JE, Chadwick AF, Craker LE. Herbs: An Indexed Bibliography 1971-1980. Hamden, CT. Archon Books. 1984.

Soares PM, Assreuy AM, Souza EP, et al. Inhibitory effects of the essential oil of Mentha pulegium on the isolated rat myometrium. Planta Medica. 2005;71(3):214-218.

Sudekum M, Poppenga RH, Raju N, Braselton WE Jr. Pennyroyal oil toxicosis in a dog. Journal of the American Veterinary Medical Association. 1992;200(6):817-818.

Sullivan JB Jr, Rumack BH, Thomas H Jr, et al. Pennyroyal oil poisoning and hepatotoxicity. Journal of the American Medical Association. 1979;242(26):2873-2874.

Sztajnkrycer MD, Otten EJ, Bond GR, Lindsell CJ, Goetz RJ. Mitigation of pennyroyal oil hepatotoxicity in the mouse. Academy of Emergency Medicine. 2003;10(10):1024-1028.

Thomassen D, Slattery JT, Nelson SD. Menthofuran-dependent and independent aspects of pulegone hepatotoxicity: roles of glutathione. Journal of Pharmacology and Experimental Therapeutics. 1990;253(2):567-572.

Toloza AC, Zygadlo J, Cueto GM, Biurrun F, Zerba E, Picollo MI. Fumigant and repellent properties of essential oils and component compounds against permethrin-resistant Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina. Journal of Medical Entomology. 2006;43(5):889-895.

Last Revised May 18, 2007

Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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