American Pennyroyal (Hedeoma pulegioides L.), European Pennyroyal (Mentha pulegium L.)


Background


The essential oil of pennyroyal is considered toxic. Death has been reported after consumption of half an ounce (15mL) of the oil. A characteristic noted in most cases of pennyroyal overdose is a strong minty smell on the patient's breath. The active metabolite menthofuran can be detected by gas chromatography in urine, blood, or other tissues. Overdose management includes oral decontamination by lavage, and/or administration of activated charcoal.

The similarity of the pathogenesis of pennyroyal-induced hepatic necrosis to that produced by acetaminophen, suggests a possible role for N-acetylcysteine (NAC) in the management of pennyroyal overdose. However, this application has not been confirmed by animal or human studies.

Anecdotal evidence and one case report suggest that the essential oil of pennyroyal may function as an abortifacient and emmenagogue (menstrual flow stimulant). However, it may do so at lethal or near-lethal doses, making this action unpredictable and dangerous. Future research to determine the safety and efficacy of the less toxic aerial parts of the pennyroyal plant on the menstrual cycle are needed before a recommendation can be made.

Synonyms


Aloe herbal horse spray, American pennyroyal, brotherwort, chasse-puces, churchwort, Cunila pulegioides , dictamne de Virginie, European pennyroyal, fleabane, flea mint, fretillet, Hedeoma phlebitides, herbal horsespray, herbe aux puces, herbe de Saint-Laurent, Labiatae (family) , la menthe pouliot (French), Lamiacea (family name), Lurk-in-the-Ditch , Melissa pulegioides , mentha pouillot, Miracle Coat spray-on dog shampoo, mock pennyroyal, mosquito plant, Old World pennyroyal, pennyroyal essential oil, petit baume, piliolerial, poley, pouliot royal, pudding herb, pudding grass, pulegium, pulegium oil, Pulegium vulgare, pulioll-royall, Pulegium regium, Run-by-the-Ground, squaw balm, squawmint, stinking balm, tickweed.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidenceGrade*Abortifacient (uterus contraction stimulant/abortion inducer)
Folkloric use and several human case reports describe use of the essential oil of pennyroyal to cause abortion. However, it may do so at deadly or toxic doses, making this an unpredictable and dangerous use.

C
Menstrual flow stimulant (emmenagogue)
Folkloric use and several human case reports describe use of the essential oil of pennyroyal as an emmenagogue (menstrual flow stimulant). However, it may do so at lethal or near-lethal doses, making this action unpredictable and dangerous.
C
* Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).


Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Acne, antiseptic, anti-spasm, anxiety, asthma, cancer, chest congestion, colds, colic, cough, cramps, diarrhea, digestion, diuretic (increasing urine flow), dizziness, dysentery, fever, flavoring agent, flea control, flu, fragrance (detergents, perfumes, soaps), gallbladder disorders, gas, gout, hallucinations, headache, hysteria, immortality, indigestion, insect repellant, intestinal disorders, itchy eyes, joint problems, kidney disease, leprosy, liver disease, bruises and burns, menstrual irregularities (stimulant, regulator), mouth sores, muscle pain, nosebleeds, pneumonia, potpourri, pregnancy, premenstrual syndrome, preparing the uterus for labor, purifier (water, blood), refrigerant, respiratory ailments, sedative, skin ailments (itching, burning, bruising), snake bites (venomous), stimulant, stomach pain, sunstroke, sweating, syncope, toothache, uterine fibroids, whooping cough.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Standardization

Standardization involves measuring the amount of certain chemicals in products to try to make different preparations similar to each other. It is not always known if the chemicals being measured are the "active" ingredients. American pennyroyal may contain up to 2% of volatile oil and European pennyroyal may contain up to 1% of volatile oil. Both oils are reported to contain 85% to 92% of the pennyroyal constituent pulegone.

Adults (18 years and older)

Note : No safe dose of pennyroyal has been established. The following doses have been used, but may be toxic.

Extract (1:2) : Doses of 20 to 40 milliliters per week of pennyroyal have been used but may be toxic.

Oil : Doses of 0.5 to 3 drops of pennyroyal oil have been used but may be toxic.

Tea/infusion : Based on traditional usage, 1 or 2 cups of tea per day made from 1 to 2 teaspoons of dried leaves per cup of boiling water, steeped for 10 to 15 minutes have been used but may be toxic. Pennyroyal tincture in tea water at doses of 0.25 to 0.5 teaspoonfuls (1.25 to 2.5 milliliters) up to twice daily for treating cough, congestion, and upset stomach, has been used but may be toxic.

Topical : Crushed plant material has been rubbed on the body as an insect repellant. Use of pennyroyal tincture mixed with skin cream and rubbed on the body has also been reported.

Veterinary : Pennyroyal has been used as an herbal flea collar for animals by hanging a bag of pennyroyal from a regular collar or using a pennyroyal garland. Safety and effectiveness of these preparations have not been proven.

Children (under 18 years old)

Pennyroyal is not recommended in children due to lack of scientific study and potential toxicity.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Allergic reactions to pennyroyal or to its components, including pulegone, may occur, although there are no reliable published reports.

Side Effects and Warnings

Pennyroyal herb and volatile oils have been associated with multiple reports of toxicity and adverse effects, including seizures, loss of consciousness, and death. In animals, pennyroyal (taken by mouth or placed on the skin) has been associated with liver, lung, and brain toxicity. Doses greater than 10 milliliters of pennyroyal may be associated with death. Cases of human overdose and death have been reported in infants, children, and adults.

Pennyroyal oil toxicity may cause nausea, vomiting, abdominal pain, burning in the throat, difficulty swallowing, diarrhea, excessive sweating, chills, fever, headache, ringing in the ears, dizziness, extreme thirst, muscle spasms, restlessness, tremor, excessive talkativeness, hallucinations, agitation, drowsiness, fatigue, confusion, mania, seizures, organ failure (brain, liver, lung, kidney, heart), altered (low or high) heart rate, altered (low or high) blood pressure, slow breathing, coma, loss of consciousness, and death. Typically, the first symptoms of poisoning, from either pennyroyal oil or pennyroyal leaves, occur in the stomach and bowels, and are often apparent soon after ingestion. Symptoms in pennyroyal overdose may mimic that of acetaminophen (Tylenol®) overdose, and the use of N-acetylcysteine (an antidote used for acetaminophen toxicity) treatment may prove beneficial.

Other side effects may include contact dermatitis, rash (when placed on the skin), malaise, lethargy, agitation, abnormal sensations, or change (increase or decrease) in pupil size. There are reports that pennyroyal may cause abortion. Pennyroyal has been used historically as an emmenagogue (menstrual stimulant) and may cause menstrual bleeding. There are reports that large amounts of pennyroyal may be irritating to the urinary tract. Pennyroyal may cause hypoglycemia (low blood sugar), hemolytic anemia (low red blood cell count due to destruction of cells), disseminated intravascular coagulation (widespread abnormal clotting and/or bleeding), and metabolic acidosis.

Pregnancy and Breastfeeding

Pennyroyal is not recommended during pregnancy or breastfeeding, due to the risk of uterine contractions, stimulation of menstruation, and abortion.

Many tinctures contain high levels of alcohol, and should be avoided during pregnancy.

References

Anderson IB, Nelson SD, Blanc PD. Pennyroyal metabolites in human poisoning. Ann Intern Med 1997;126(3):250-251.
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(8):726-734.
Bakerink JA, Gospe SM, Jr., Dimand RJ et al. Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants. Pediatrics 1996;98(5):944-947.
Black DR. Pregnancy unaffected by pennyroyal usage. J Am Oseopath Assoc 1985;85(5):282.
Buechel DW, Haverlah VC, Gardner ME. Pennyroyal oil ingestion: report of a case. J Am Osteopath Assoc 1983;82 (10) :793-794.
Burkhard PR, Burkhardt K, Haenggeli CA, et al. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246(8):667-670.
Carmichael PG. Pennyroyal metabolites in human poisoning. Ann Intern Med 1997;126(3):250-251.
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Gordon WP, Forte AJ, McMurtry RJ, et al. Hepatotoxicity and pulmonary toxicity of pennyroyal oil and its constituent terpenes in the mouse. Toxicol Appl Pharmacol 1982;65(3):413-424.
Khojasteh-Bakht SC, Chen W, Koenigs LL, et al. Metabolism of (R)-(+)-pulegone and (R)-(+)-menthofuran by human liver cytochrome P-450s: evidence for formation of a furan epoxide. Drug Metab Dispos 1999;27(5):574-580.
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January 01, 2004