What Is Pennyroyal?

Traditional Abortion-Inducting Herb Is Unsafe to Ingest in Any Form

Pennyroyal topical oil

Verywell / Anastasia Tretiak

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Pennyroyal (Mentha pulegium L.) a medicinal herb in the Lamiaceae (mint) family, is commonly known by other names, including European pennyroyal, pennyrile, squaw mint, mosquito plant, and pudding grass. Both Hedeoma pulegioldes (American pennyroyal) and Mentha puleguim (European pennyroyal) are referred to as pennyroyal. They are both creeping plants with small lilac flowers and grayish-green leaves.

Pennyroyal extract contains the volatile oil pulegone, which was used as a traditional folk remedy, to induce abortion (in high doses) or stimulate menstruation (in lower doses). Pennyroyal leaf extracts have been used to flavor food and wine and to make tea because the leaves of the pennyroyal plant are more aromatic (minty flavored) than other mint varieties. Its volatile oil, however, being much more concentrated than the leaves of the plant, is considered very toxic, even in small doses.

Pennyroyal oil should never be taken internally.

The dose at which pennyroyal can cause abortion is also a lethal dose to the woman taking it. The herbal supplement is not considered safe to ingest for any use.


Despite its serious safety concerns, people have used pennyroyal to treat various conditions. But there is a lack of clinical research evidence to back up the claims for safe and effective use of pennyroyal.

Pennyroyal is sometimes applied to the skin (topical use) for gout. Ingestion is not recommended due to toxicity concerns, but some people have used the leaves or an infusion (tea) for complaints such as breathing problems, stomach pains, or gas.

The traditional uses of pennyroyal include regulating menstrual periods, inducing abortion, controlling muscle spasms, inducing sweating, increasing urine production, and to kill bacteria on the skin. As well, it was sometimes used against tuberculosis or smallpox.

Pennyroyal has been used as a pest repellant and insecticide to keep fleas away from pets and humans and to repel mosquitos, gnats, and other pests. If the plant is used as an insecticide or repellant, the crushed leaves should be used instead of the oil, because the leaves are much less toxic than the oil. 

Some flea collars have pennyroyal oil. However, experts advise that pennyroyal oil should never be used topically (on the skin) on humans or animals, because of its toxic properties.

In addition to the fact that pennyroyal has been linked to severe side effects (such as irreversible kidney or liver damage, organ failure, and death) there is not enough clinical research evidence to support its effectiveness in treating any type of illness.

The exact way that pennyroyal works to induce abortions, or to provide purported health benefits, is unknown. 

Possible Side Effects

Special Warning

There have been many reports of toxicity from pennyroyal oil—usually within only a few hours of use.

Just one tablespoon (15 ml) of pennyroyal oil has been known to cause seizures, coma, severe liver and kidney damage, and cardiopulmonary collapse—leading to failure of vital organs and death.

Early signs and symptoms of pennyroyal oil poisoning may include:

  • Nausea and vomiting
  • Agitation and confusion
  • Abdominal pain

More severe signs and symptoms of pennyroyal toxicity may include:

  • Cardiovascular collapse
  • Disseminated intravascular coagulation: A condition in which small blood clots develop throughout the bloodstream, this results in excessive bleeding (as a result of the body’s clotting factors being used up), and can be fatal.
  • Acute liver injury
  • Early liver failure
  • Death

When a person is diagnosed with pennyroyal oil poisoning, unfortunately, there is not an antidote available, thus, prevention and early intervention are important.

One treatment that has been used is glutathionine (amino acids), which may slow down the toxic effects of pulegone, but this is only available with early intervention. Also, there is a lack of evidence as to the safety and effectiveness of gluthathionine for treating pennyroyal poisoning.

Side Effects

Side effects from the use of pennyroyal may include:

  • Dermatitis (itchy skin)
  • Nausea
  • Vomiting
  • Increase in blood pressure
  • Increase in pulse rate
  • Hallucinations
  • Seizures
  • Liver toxicity
  • Nerve toxicity
  • Delirium
  • Shock


Pennyroyal is no longer recommended for any type of use, but it is particularly unsafe in some conditions, including:

  • Kidney disease: The oil in pennyroyal may irritate the kidneys, worsening existing kidney disorders
  • Pregnancy: Pennyroyal leaf tea (or oil) can start menstruation; this could abort the pregnancy
  • Breastfeeding: Pennyroyal is not safe for breastfed infants
  • Children: Pennyroyal is unsafe for children; there are reports of two infants who developed severe liver and nervous system problems after taking pennyroyal, and one of the infants died.
  • Liver disease: Pennyroyal is known to cause liver damage and it may worsen an existing liver condition

Working with products made of pennyroyal oil may cause health problems even if pennyroyal products are not ingested. This is because the volatile oil can be absorbed through the skin, resulting in serious side effects.

Selection, Preparation, and Storage

Because of the proven toxic effects of pennyroyal, there are no recommendations on how to purchase the herbal supplement or the essential oil form of the plant.

There is no safe dosage of pennyroyal, the plant has been known to be severely toxic at doses as small as 5 grams.


The part of the pennyroyal plant that is used is the aerial portion, harvesting is optimal right before the flowering stage of the plant. Pennyroyal leaves are sometimes used to make a tea. Not enough is known about the safe use of pennyroyal leaf to consider ingestion (in any form, including tea).

There is also an extract form. Pennyroyal oil is available, but it is not recommended for internal use.

Other Questions

Is there any type of safe use of the pennyroyal plant?

Pennyroyal is said to be a good herb to plant in gardens to keep bugs away.

Is pennyroyal safe for dogs or any other pets?

No. Animal studies report that pennyroyal oil has caused liver damage and death within a few hours of the oil being used to treat fleas.

Can the pennyroyal plant be eaten?

No. There is not enough clinical research to indicate that pennyroyal is safe to ingest in any form.

What is the history of pennyroyal?

Historically, pennyroyal has been used as far back as the first century C.E., as it was recorded by Roman naturalists and Greek physicians. Later, during the 17th century, Nicholas Culpeper, the famous English herbalist, wrote about the use of pennyroyal to treat women’s conditions and poisonous snake bites, and to improve digestion. The oil from the plant was used to kill fleas, thus the name “pulegioides,” from the Latin word for flea.

A Word From Verywell

Although there are herbalists who still recommend pennyroyal use to treat various conditions, we at Verywell Health do not recommend its use in any type of preparation, to treat any condition. This includes ingesting pennyroyal as a tea, extract or tincture, using it topically (on the skin) for any reason (including as a pesticide) or using pennyroyal to repel pests from pets. If you, or someone you know, has swallowed pennyroyal oil, contact Poison Control, immediately at 1-800-222-1222.

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Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Clinical Research Information on Drug-Induced Liver Injury. Drug Record. PENNYROYAL OIL (MENTHA PULEGIUM). Updated July 01, 2019.

  2. National Institutes of Health. Clinical Research Information on Drug-Induced Liver Injury. PENNYROYAL OIL (MENTHA PULEGIUM). Updated July 01, 2019.

  3. Mekonnen, S. Pennyroyal Oil. A Potentially Toxic Folk Remedy. Poison Control. National Capital Poison Center. Updated September 30, 2016.

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