# Plant Monograph: Pennyroyal
**Name of plant:**
Pennyroyal
**Catch phrase (Carmina Gadelica or traditional invocation if available):**
No Carmina Gadelica invocation is associated with Pennyroyal. No securely documented traditional Gaelic invocation specific to the plant has been identified. A traditional European association is appropriate: **“Herb of the little royal.”** The name *pennyroyal* is generally traced through Middle English/French forms ultimately associated with Latin *pulegium*, rather than with an actual royal invocation.
**Family:**
Lamiaceae — the mint family
**Genus and species:**
*Mentha pulegium* L.
**Other names:**
* Pennyroyal
* European pennyroyal
* English pennyroyal
* Pudding grass
* Mosquito plant
* Fleabane
* Pulegium
* *Mentha pulegium*
* Pouliot — French
* Poleo — Spanish
* Polei — German
* Pennyroyal mint
**Brief introduction:**
Pennyroyal is a strongly aromatic perennial mint native to Europe, North Africa, and parts of the Middle East. It typically grows as a low, spreading herb with small leaves and whorls of lilac to pink flowers. It favours moist ground, meadows, stream margins, marshy areas, and other habitats where the soil remains reasonably damp.
The plant has a long history as a culinary herb, insect repellent, and folk medicine. Its distinctive aroma comes principally from **pulegone**, a monoterpene ketone that may constitute a very large proportion of its essential oil. This same constituent is responsible for much of pennyroyal's toxicological importance. Modern safety literature distinguishes sharply between traditional use of the herb and **pennyroyal essential oil, which is highly toxic and has caused severe liver injury and death**. ([PubMed][1])
**Traditional uses:**
* Used as a carminative for flatulence, intestinal discomfort, and digestive upset
* Traditionally taken for menstrual complaints and to encourage menstruation
* Used historically for colic, hiccups, and digestive spasms
* Applied or burned as an insect and flea repellent
* Used traditionally for colds, coughs, fever, rheumatic complaints, and other respiratory or inflammatory conditions ([PubMed][1])
**Historical use:**
* Pennyroyal was used throughout European folk medicine as an aromatic digestive herb
* Its strong fragrance led to its use in household insect and flea control
* The herb was historically included in preparations intended to stimulate menstruation
* Pennyroyal acquired a notorious reputation as an abortifacient; this historical use is important ethnobotanically but is **dangerous and not a medically acceptable method of inducing abortion**
* Moroccan traditional medicine continues to document uses of *M. pulegium* for digestive, respiratory, inflammatory, and other complaints ([PubMed][1])
**Parts used and method of use:**
* Leaves and flowering aerial parts
* Essential oil — historically used externally, as a fragrance, and as an insect repellent, but **not appropriate for internal use**
Used as:
* Herbal infusion or tea in historical folk practice
* Fresh or dried culinary herb
* External wash or aromatic preparation
* Dried herb used as an insect-repellent material
**Use in healing (modern herbal practice):**
* Traditionally used as a carminative and digestive herb
* Historically used for intestinal colic, flatulence, and dyspepsia
* Traditionally employed for coughs and minor respiratory complaints
* Historically used for menstrual irregularity and painful menstruation
* Investigated experimentally for antimicrobial, antioxidant, anti-inflammatory, antispasmodic, and other pharmacological properties, although human clinical evidence remains inadequate ([PubMed][1])
**Pharmacology and biochemistry:**
* **Pulegone** — the principal volatile constituent and major toxicological concern
* **Menthofuran** — an important metabolite of pulegone and contributor to hepatotoxicity
* **Menthone, isomenthone, piperitone, menthol, and flavonoids** — additional constituents whose proportions vary substantially with geography, chemotype, growth conditions, and extraction method ([PubMed][1])
Mechanisms:
* Pulegone is metabolized in the liver through cytochrome P450 pathways, producing reactive metabolites associated with hepatic injury
* Metabolism through menthofuran and subsequent reactive intermediates can cause oxidative and covalent damage to hepatic cellular components
* Experimental studies demonstrate antimicrobial, antioxidant, anti-inflammatory, and antispasmodic activities, but these effects occur alongside significant toxic potential ([ScienceDirect][2])
Overall profile: Pennyroyal is a **pharmacologically active but hazardous mint**. Its traditional digestive and aromatic uses are well documented, but its pulegone-rich essential oil has a narrow safety margin and can cause severe hepatotoxicity, renal injury, seizures, and death. Pennyroyal oil should **never be taken internally**. ([Poison Control][3])
**Common dosage:**
* **Culinary herb:** Small quantities as a flavouring; no medicinal dose implied
* **Traditional leaf infusion:** Historically prepared as a weak tea, but no reliably established modern therapeutic oral dose can be recommended because pulegone content varies
* **Liquid extract/tincture:** No established safe therapeutic dosage
* **Essential oil:** **No oral dosage — internal use is contraindicated because of serious toxicity** ([PubMed][1])
**Safety factors (including side effects):**
* **Pennyroyal essential oil is highly toxic** and has caused severe poisoning, liver failure, multiple-organ failure, and death
* Oral exposure can initially cause nausea, vomiting, abdominal pain, dizziness, weakness, and agitation, followed by potentially severe hepatic injury
* Pennyroyal should **not be used during pregnancy**; its historical reputation as an abortifacient reflects dangerous poisoning rather than a safe therapeutic effect
* Children and infants are particularly vulnerable; pennyroyal preparations should not be given to them
* Prolonged or concentrated exposure may produce serious hepatic and renal toxicity; the essential oil should not be used internally or as a home medicinal preparation ([Poison Control][3])
**First aid / adverse reaction response:**
* **Nausea, vomiting, or abdominal pain after ingestion:** Stop exposure and contact a poison centre promptly
* **Dizziness, weakness, confusion, or unusual sleepiness:** Seek urgent medical assessment because these can accompany systemic poisoning
* **Seizures, difficulty breathing, severe bleeding, or collapse:** Call emergency services immediately
* **Suspected ingestion of pennyroyal essential oil:** Treat as a potential poisoning emergency; do **not** induce vomiting unless specifically instructed by poison-control personnel. There is no specific antidote, making early supportive treatment especially important. ([Poison Control][3])
**Drug interactions:**
* May compound **hepatotoxicity** when combined with other substances capable of damaging the liver
* Theoretical interaction is possible with medicines metabolized through hepatic cytochrome P450 systems because pulegone undergoes extensive hepatic metabolism
* Because pennyroyal preparations can vary enormously in pulegone concentration, concentrated extracts should not be combined casually with prescription medicines
* General interaction consideration: anyone taking medications with significant hepatic toxicity or undergoing treatment for liver disease should avoid medicinal pennyroyal unless specifically supervised by a qualified clinician
**Horticultural requirements:**
* **USDA / Canadian zone:** Approximately USDA Zones 6–9; hardiness varies with population and local conditions
* **Soil pH:** Approximately 6.0–7.5
* **Light requirements:** Full sun to partial shade
* **Moisture:** Moist to moderately moist; tolerates wet soils better than many culinary mints
* **Other notes (growth habit, harvest timing, etc.):**
* **Growth habit:** Low-growing, spreading perennial mint, commonly approximately 20–50 cm tall
* **Flowering/fruiting:** Small lilac, pink, or purple flowers occur in dense whorls around the stems during summer
* **Harvest timing:** Aerial portions are traditionally gathered shortly before or during flowering, when aromatic constituents are abundant
* **Habitat:** Moist meadows, stream margins, marsh edges, damp grassland, and disturbed ground
* **Propagation/cultivation notes:** Easily propagated by division or cuttings and can spread vigorously. Cultivation should be controlled to prevent unwanted naturalization. Chemotype and growing conditions can substantially alter essential-oil composition.
**Sampling of clinical reports / studies:**
* **Clinical study or report:** Human clinical evidence supporting therapeutic use is sparse; documented poisoning cases provide considerably stronger evidence concerning the risks of pennyroyal oil. Historical case reports include severe hepatotoxicity and fatal poisoning. ([Poison Control][3])
* **Pharmacological study:** Experimental studies report antimicrobial, antioxidant, anti-inflammatory, antispasmodic, and other activities in *M. pulegium* extracts and essential oil. ([PubMed][1])
* **Phytochemical study:** Essential-oil analyses repeatedly identify pulegone as a dominant constituent, although concentrations vary markedly among samples; menthone and piperitone are also frequently present. ([IADNS][4])
* **Ethnobotanical evidence:** European, North African, and Middle Eastern traditions document pennyroyal as a digestive, aromatic, respiratory, menstrual, and insect-repellent herb. ([PubMed][1])
* **Overall assessment of evidence:** **Strong historical and ethnobotanical evidence; substantial experimental pharmacology; inadequate clinical evidence; and very strong evidence of toxicity for the essential oil.** For an apothecary monograph, pennyroyal should be marked as a **high-caution herb**, with particular emphasis that pennyroyal oil is not an appropriate internal remedy. ([Poison Control][3])
[1]: https://pubmed.ncbi.nlm.nih.gov/37711001/?utm_source=chatgpt.com "Mentha Pulegium: A Plant with Several Medicinal Properties - PubMed"
[2]: https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/pulegone?utm_source=chatgpt.com "Pulegone - an overview | ScienceDirect Topics"
[3]: https://www.poison.org/articles/pennyroyal-oil?utm_source=chatgpt.com "Pennyroyal oil: A potentially toxic folk remedy | Poison Control"
[4]: https://iadns.onlinelibrary.wiley.com/doi/10.1002/fft2.53?utm_source=chatgpt.com "Recent advances in genus Mentha: Phytochemistry, antimicrobial effects, and food applications - Mamadalieva - 2020 - Food Frontiers - Wiley Online Library"
Educational Use Only: The information presented on this page is provided for educational, historical, and informational purposes only. ArdNemeton na Tuatha and Bhùth Draoi do not provide medical advice. Always consult your physician and pharmacist before using any herb, mushroom, supplement, or botanical product for medicinal purposes. Traditional uses described herein do not constitute medical claims.