Reviewed by Terri Forehand RN

Pennyroyal (Mentha pulegium and Hedeoma pulegoides) is a member of the mint family. The herb has a history of being used medicinally but unlike most other mint species, pennyroyal is toxic.


Pennyroyal grows up to two feet tall. It is a perennial and has oval green leaves and bluish-purple or pink whorls. The herb is native to Europe and parts of Asia but is now plentiful in North America, especially in sunny woodland areas, and is invasive.

Pennyroyal has a powerful, bitter odor and minty taste.


Both the essential oil and leaves of pennyroyal are used in therapeutic preparations. Pennyroyal is also used to repel insects.

Medicinal Uses

Medline Plus (Medline) mentions the following uses for the pennyroyal but also says there is insufficient evidence to support its effectiveness:

  • As an abortifacient
  • To regulate or start menstruation
  • Control muscle spasms
  • Cause sweating
  • Increase urine production
  • Increase strength
  • To treat stomach pains and intestinal issues
  • To treat liver and gall bladder trouble
  • To treat colds and respiratory problems

Insect Repellent

Pennyroyal can be grown in a garden or pot or around the perimeter of a home to help repel insects. It is also used as a flea and tick repellent for pets; however, pennyroyal essential oil may pose high risk to pets. Pets may experience the same toxic side effects as humans when ingesting pennyroyal.

Even though pennyroyal is used externally as a flea repellent, animals may lick the oil and experience toxicity. As a result, it is not recommended that pennyroyal be used on animals.


Pennyroyal essential oil is sometimes used in aromatherapy as a massage oil or foot rub. Home Remedy Central states on its website that pennyroyal essential oil should not be used in aromatherapy due to potential toxicity.

External Use

Fresh pennyroyal herb may be crushed in an infusion for external use. Wet pennyroyal tea bags are sometimes used on the skin to repel insects or relieve bites. However, you should only use pennyroyal externally under the instruction of a natural health practitioner or your physician.

Side Effects

Medline classifies pennyroyal as unsafe. The herb may cause liver, kidney or nervous system damage. In addition, pennyroyal may cause the following significant and dangerous side effects:

  • Stomach pain
  • Nausea and vomiting
  • Throat burning
  • Fever
  • Confusion
  • Restlessness
  • Seizures
  • Dizziness
  • High blood pressure
  • Abortion
  • Vision and hearing problems
  • Lung failure
  • Brain damage

Medline warns that pennyroyal essential oil is unsafe for everybody but mention the following special precautions:

  • Children should never use pennyroyal. After being given the herb, two infants "developed serious liver and nervous system injuries." One infant died.
  • Pregnant women should avoid pennyroyal in all forms, including pennyroyal leaf tea. It may cause the uterus to contract and cause an abortion (Medline also indicates that the amount of pennyroyal needed to cause an abortion would also likely kill the mother or lead to life-long liver and kidney problems).
  • Pennyroyal may worsen existing liver or kidney disease.

Do Not Ingest Pennyroyal Oil

Many people assume that because herbs are natural they are safe. But that is not necessarily the case. Pennyroyal is a lovely plant that offers insect repelling properties when growing wild or planted outdoors (away from the curious hands of children or from nosy pets). However, its essential oil should not be ingested. states that pennyroyal herbal tea is considered safe to use because of its low concentration of essential oils. Consult your physician or a natural health practitioner before using pennyroyal in any form.

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