Pennyroyal

Traditionally, pennyroyal has been used primarily as an insect repellent and, historically, as an emmenagogue to bring on delayed menstruation, though modern herbal practice has largely moved away from internal use given serious, well-documented safety concerns. It is commonly used today as a dried herb sachet or diluted oil for repelling insects, with internal and concentrated oil use no longer recommended.

Common Name: Pennyroyal Latin Name: Mentha pulegium Alternate Names: Squaw mint, pudding grass

• Parts used: leaves and flowering tops
• Primary properties: insect-repellent, historically emmenagogue
• Common preparations: dried herb sachet, heavily diluted topical oil (external use only)
• Best known for: repelling insects; historically used internally, now understood to carry serious risk

Health Conditions Pennyroyal Helps With

• Insect and flea deterrence — Pennyroyal’s strong aroma has a long traditional and modern reputation for repelling fleas, mosquitoes, and other insects, and this remains its main legitimate current use.
• Historical use for delayed menstruation — Pennyroyal has a centuries-long traditional history as an emmenagogue, taken to bring on delayed menses; this internal use is no longer recommended given the well-documented toxicity of the plant’s essential oil.
• Historical folk use for colds and digestive complaints — Older folk tradition includes pennyroyal tea for coughs, colds, and mild indigestion, though this internal use has also fallen out of favor given modern safety findings.

Given how serious pennyroyal’s documented risks are, this post focuses primarily on safety rather than encouraging use, and its only currently recommended application is external, highly diluted, insect-repellent use.

Compounds

• Pulegone — The dominant compound in pennyroyal’s essential oil, responsible for both its aroma and its well-documented toxicity to the liver, kidneys, and nervous system.
• Menthofuran — A toxic metabolite formed when the body processes pulegone, directly responsible for much of the serious organ damage associated with pennyroyal poisoning.
• Menthone — A related monoterpene contributing to pennyroyal’s characteristic minty scent and some of its insect-repellent activity.
• Other monoterpenes — Contribute to the plant’s aroma and repellent qualities.

Properties

• Insect-repellent — Pennyroyal’s strong aroma is the basis for its one clearly recommended modern use, applied externally and in properly diluted form only.
• Historically emmenagogue — Traditionally believed to stimulate menstrual flow, though this action is inseparable from the plant’s serious, dose-related toxicity and is not a safe or reliable use.
• Hepatotoxic (in concentrated or internal form) — Not a traditional “benefit,” but a defining, well-documented property of pennyroyal oil and concentrated internal preparations that anyone considering this herb needs to understand clearly.

Recipes Using Pennyroyal

• Dried herb sachets or repellent pouches — Dried pennyroyal leaf placed in sachets or pouches, traditionally used to deter fleas and moths from stored fabric or bedding, without any oil concentration or ingestion involved.
• Properly diluted topical insect repellent — Pennyroyal essential oil, when used at all, is only used externally and in very low, properly diluted concentrations as an occasional insect deterrent, never applied undiluted or taken internally.

This post intentionally does not include internal preparations such as tea or tincture recipes, given the well-documented risk associated with ingesting pennyroyal in any concentrated form.

Products Featuring Pennyroyal

• Dried herb — Used in sachets or repellent pouches; internal use of dried herb tea is not recommended given documented cases of serious toxicity even from tea, particularly in children.
• Essential oil (external use only) — Should only ever be used externally, in properly diluted form, and never ingested under any circumstances, given its documented potential for severe, sometimes fatal toxicity even in small amounts.

Synergies

Because pennyroyal’s only currently recommended use is as an external insect repellent, and because combining it with other herbs for internal use isn’t advisable, this section is intentionally limited. For insect-repellent blends, pennyroyal is sometimes combined with other aromatic repellent herbs like lavender or eucalyptus in sachets, valued for their shared strong scent rather than any internal herbal synergy.

Safety & Precautions

Pennyroyal, particularly its essential oil, is one of the more seriously toxic botanicals still found in herbal folklore, and this section carries real weight — please read it in full before considering any use of this plant.

Pennyroyal oil should never be taken internally under any circumstances. Documented cases of severe poisoning, including liver failure, kidney failure, seizures, and death, have occurred from ingesting pennyroyal oil, sometimes from doses as small as a tablespoon or less; even pennyroyal tea has caused serious, sometimes fatal toxicity, including in infants and children. Pennyroyal should never be given to children in any internal form. Pennyroyal must never be used with the intention of inducing abortion or delayed menstruation; historical use for this purpose required doses that are inherently dangerous to the person taking them, the effect is unreliable, and it has caused documented maternal deaths without reliably ending a pregnancy — this is not a safe or effective method for any purpose, and anyone facing an unwanted pregnancy should seek care from a licensed medical provider rather than any herbal remedy. Pennyroyal should be avoided entirely during pregnancy and breastfeeding in any form. Topical or diluted use should be approached cautiously as well, avoiding use on broken skin, in young children, or during pregnancy, and a patch test is advisable given the potential for skin irritation. Pennyroyal essential oil is also toxic to pets, particularly cats and dogs, and should never be used as a flea or insect repellent directly on animals or in a form they could ingest or absorb; if a pet is exposed, contacting a veterinarian immediately is essential.

Q&A

Does pennyroyal taste bitter?

Pennyroyal has a strong, sharp, minty flavor rather than a true bitterness, similar to a more intense, pungent version of spearmint or pennyroyal’s other mint relatives.

That said, taste isn’t the relevant consideration here — pennyroyal is not recommended for internal use in any form, tea included, given documented cases of serious toxicity even from tea preparations.

Can pennyroyal be used daily?

No — pennyroyal is not recommended for internal use at all, daily or otherwise, given its well-documented potential for serious, sometimes fatal toxicity even in small amounts.

For its one currently recommended use, as an external, diluted insect repellent, it should still be used sparingly and only as needed, not as a daily topical habit, given the potential for skin irritation with repeated exposure.

Is pennyroyal tea safe?

No — while pennyroyal tea was used historically, modern documentation includes cases of serious and even fatal toxicity from pennyroyal tea, including in infants and children, so it is not considered safe for internal use today.

If you’re looking for a safe, calming mint tea, culinary mints like peppermint or spearmint are a much safer and equally aromatic alternative that don’t carry pennyroyal’s documented risks.

Is it true pennyroyal was historically used to end pregnancies?

Yes, this is a well-documented historical use, but it’s important to understand clearly that the doses required were inherently dangerous to the person taking them, the effect was unreliable, and it has caused real, documented deaths without reliably ending a pregnancy.

This is not a safe or effective method for pregnancy termination by any measure, and anyone facing this situation should speak with a licensed medical provider about safe, effective, legal options rather than turning to this or any herbal remedy.

Is pennyroyal safe to use around pets?

No — pennyroyal essential oil is toxic to pets, particularly cats and dogs, and should never be applied directly to animals as a flea repellent or used in a form they could lick, inhale heavily, or ingest.

If you suspect a pet has been exposed to pennyroyal oil, contacting a veterinarian right away is the safest course of action, since animal toxicity from this plant has also been documented.

References

• Plants of the World Online: Mentha pulegium
• PubMed: Scientific Literature on Mentha pulegium
• National Library of Medicine: Pulegone Toxicity Research
• Wikipedia: Mentha pulegium
• Memorial Sloan Kettering Cancer Center: About Herbs — Pennyroyal
• NCBI Bookshelf: LiverTox — Pennyroyal Oil
• National Center for Complementary and Integrative Health: Pennyroyal Safety