Pennyroyal

Scientific Name(s): Hedeoma pulegioides (L.) Persoon (American), Mentha pulegium L. (European)
Common Name(s): American pennyroyal, European pennyroyal, False pennyroyal, Mosquito plant, Pudding grass, Squawmint

Medically reviewed by Drugs.com. Last updated on Jul 14, 2023.

Clinical Overview

Use

Clinical studies are lacking to provide guidance on therapeutic applications due to the plant’s toxicity.

Dosing

Pennyroyal oil is not recommended for internal or topical use. There are no clinical studies of pennyroyal herbal tea to provide dosing guidance. Pulegone-free preparations should be used.

Contraindications

Pennyroyal oil is not recommended for internal or topical use.

Pregnancy/Lactation

Avoid use. Abortifacient, hepatotoxic, neurotoxic, and carcinogenic adverse effects have been reported.

Interactions

None well documented.

Adverse Reactions

Pennyroyal oil is not recommended for internal or topical use due to abortifacient, hepatotoxic, neurotoxic, and carcinogenic properties. Although pennyroyal herbal teas have generally been used without reported adverse effects, pulegone-free preparations are recommended. Allergic reactions to the plant, including contact dermatitis and generalized urticaria, have been reported.

Toxicology

The toxicity of pennyroyal oil is well recognized, with many documented reports of adverse events and fatalities. In humans, consumption of 10 mL of the oil has resulted in moderate to severe toxicity, with case reports of fatalities 1 to 2 hours after consumption of 15 mL. Symptoms of toxicity include abdominal cramping and pain, nausea, vomiting, rash, dizziness, alternating lethargy and agitation and other CNS symptoms (including seizures), renal and hepatic failure, and disseminated intravascular coagulation. Early administration of acetylcysteine to restore glutathione levels and of cytochrome P450 (CYP-450) activators cimetidine and disulfiram may counteract the putative effects of pulegone.

Scientific Family

• Lamiaceae (mint)

Botany

American and European species of pennyroyal plant are members of the mint family (Lamiaceae family [formerly Labiatae]), and both are referred to as "pennyroyal." H. pulegioides (American pennyroyal) grows in woods throughout most of the northern and eastern United States and Canada, while M. pulegium is found in parts of Europe. Pennyroyal is a perennial creeping herb with small lilac flowers at the stem ends. It can grow to be 30 to 50 cm in height. Like other mint family members, the grayish-green leaves are very aromatic.Duke 2002, USDA 2015 A synonym of H. pulegioides is Melissa pulegioides L. A synonym of M. pulegium is Pulegium vulgare Mill.

History

Use of pennyroyal was recorded as early as the first century AD, by the Roman naturalist Pliny and the Greek physician Dioscorides. In the 17th century, English herbalist Nicholas Culpeper described the plant's role in women's ailments, venomous bites, and digestion. European settlers used the plant for respiratory ailments, mouth sores, and female disorders.Cartwright 1994 The plant's oil has been used as a flea-killing bath, hence the name "pulegioides" (from the Latin word meaning flea), and has been used externally as a rubefacient. The oil has also been frequently used among natural health advocates as an abortifacient and to induce delayed menses. The oil and infusions of the leaves have been used to treat weakness and stomach pains, among other indications.Da Legnano 1973, Duke 2002

Chemistry

The leaves and flowering tops are the source of the essential oil, which has a concentration of 1% to 2%, depending on the genus. The phenolic composition of the aqueous extract has been described and includes flavonoids (luteolin, apigenin, naringenin, catechin, rutinoside, jaceosidin, and others) and phenolic acids (including caffeic, vanillic, ferulic, rosmarinic, and lithospermic).Duke 1992, Ferreres 2015, Kogiannou 2013 Antioxidant activity of pennyroyal tea due to the phenolic content has been demonstrated.Kogiannou 2013

The essential oil is rich in monoterpenes, especially pulegone (also found in peppermint oil) and its metabolite menthofuran, with piperitone oxide, isopulegol, piperitone, and piperitenone also described, as well as monoterpene hydrocarbons and sesquiterpenoids.Díaz-Maroto 2007, Duke 1992 Techniques for quantification of components have been described.Díaz-Maroto 2007, Ferguson 2007

Uses and Pharmacology

Insecticide/Antimicrobial activity

Animal data

Studies suggest insect repellant and insecticidal activity, probably due to the essential oil vapor. Although activity against head lice (Pediculus humanus capitis) has been demonstrated,Yang 2004 topical application of pennyroyal is not recommended due to toxicity related to skin absorption. The moderate repellant activity observed against wasps may be due to pulegone, eugenol, citral, and other chemicals.Zhang 2013

Pennyroyal (dried, whole plant) administered to chickens in their feed reduced the presence of intestinal Escherichia coli, with no apparent adverse effects.Erhan 2012

Clinical data

Clinical studies are lacking to provide guidance on therapeutic applications due to the plant's toxicity.

Dosing

Pennyroyal oil is not recommended for internal or topical use.Anderson 1996, Duke 2002, Samuels 2008 There are no clinical studies of pennyroyal herbal tea to provide dosing guidance. Pulegone-free preparations should be used. One safety assessment of peppermint oil indicated that the concentration of pulegone should not exceed 1%.Nair 2001 Pennyroyal is also present in certain multi-ingredient preparations.Ciganda 2003

Pregnancy / Lactation

Avoid use. Abortifacient, hepatotoxic, neurotoxic, and carcinogenic adverse effects have been reported.Anderson 1996, Ciganda 2003, Duke 2002, Ernst 2002, Samuels 2008

In a study using isolated rat uterine myometrial tissue, Mentha pulegium oil’s inhibition of contractile activity was similar to that of the calcium channel blocker nifedipine.Soares 2005

Interactions

None well documented. Case reports are lacking.

Adverse Reactions

Pennyroyal oil is not recommended for internal or topical use. Abortifacient, hepatotoxic, neurotoxic, and carcinogenic adverse effects have been reported.Anderson 1996, Ciganda 2003, Duke 2002, Ernst 2002, Samuels 2008

Although pennyroyal herbal teas have generally been used without reported adverse effects, pulegone-free preparations are recommended.Duke 2002 Allergic reactions to the plant, including contact dermatitis and generalized urticaria, and a case of postpartum hemorrhage have been reported.Dennehy 2010, Pérez-Calderón 2007, Roé 2005

The European Association for the Study of the Liver (EASL) clinical practice guideline for drug-induced liver injury (2019) recommends physicians consider herbal and dietary supplements as potential causative agents associated with liver injury (Level 4; Grade C), including pennyroyal, which has some of the highest levels of evidence supporting hepatotoxicity.EASL 2019

Toxicology

The toxicity of pennyroyal oil is well recognized, with many documented reports of adverse events and fatalities. In humans, consumption of 10 mL of the oil has resulted in moderate to severe toxicity, with case reports of fatalities 1 to 2 hours after consumption of 15 mL.Bunchorntavakul 2013 In rats, the median lethal dose (LD₅₀) of pennyroyal essential oil is reported to be 400 mg/kg.Duke 2002

Toxicity is likely the result of the direct action of pulegone on glutathione, as well as the action of its toxic metabolite menthofuran.Bunchorntavakul 2013, Gordon 2015, Samuels 2008, Seeff 2007 Symptoms of toxicity include abdominal cramping and pain, nausea, vomiting, rash, dizziness, alternating lethargy and agitation and other CNS symptoms (including seizures), renal and hepatic failure, and disseminated intravascular coagulation.Bunchorntavakul 2013, Duke 2002, Gordon 2015, Samuels 2008, Seeff 2007

Early administration of acetylcysteine to restore glutathione levels and of cytochrome P450 (CYP-450) activators cimetidine and disulfiram may counteract the putative effects of pulegone based on one case report.Anderson 1996, Bunchorntavakul 2013 Studies in rodents have suggested that CYP-450 activators cimetidine and disulfiram may also counteract the putative effects of pulegone on the liver.Seeff 2007, Sztajnkrycer 2003

Evidence of cytotoxicity in rodents has been reported, with an increase in liver neoplasms observed. Equivocal results for mutagenicity of pulegone have suggested that the chemical is a non-DNA–reactive carcinogen.Da Rocha 2012

Index Terms

• Melissa pulegioides L.
• Pulegium vulgare Mill.
• Labiatae

References

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This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

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