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Overview: Pennyroyal is a plant called Mentha pulegium. People use pennyroyal for digestive problems and colds and as an insect repellent, among other uses. However, it has serious risks, and its benefits for any use are not well defined. Pennyroyal oil is highly toxic and has been linked to serious liver damage, kidney damage, seizures, and death. Check with your health care provider before using pennyroyal for any reason.

Uses

What is pennyroyal used for?

Pennyroyal (Mentha pulegium) is used for various reasons, but its benefits are not well defined. Some reasons for using pennyroyal include the following.

  • Insect repellent or wound healing (when applied to the skin)
  • Digestive problems, such as gas, nausea, or upset stomach
  • Colds and cough

Pennyroyal oil has also been used to end pregnancy (induce abortion), which is extremely dangerous and has led to deaths of pregnant people. If you are thinking about ending a pregnancy, do not use pennyroyal. Instead, talk to a health care provider about your options.

Note: The FDA has not reviewed pennyroyal for safety and effectiveness. Learn more about dietary supplements here.

How does pennyroyal work (mechanism of action)?

Pennyroyal is a type of mint plant called Mentha pulegium. It is also sometimes called squawmint, pudding grass, mosquito plant, or other names. Pennyroyal products are usually made from the leaves and stems of the plant.

Pennyroyal contains a chemical called pulegone, which makes up a large portion of the oil and is responsible for its poisonous effects. When the body breaks down pulegone, it produces other harmful substances that can damage liver cells. Pulegone also lowers the body’s levels of glutathione, a natural substance that helps protect the liver from damage. Together, these effects can lead to severe liver injury.

Pennyroyal has been used as a digestive aid because it may help relax smooth muscles in the intestines. Pennyroyal has also shown some ability to fight germs in lab studies. However, there is not enough reliable research to know whether pennyroyal works for any health condition in people. Most of the available research has been done in test tubes or animals, not in humans.

Even small amounts of pennyroyal oil has led to severe and fatal cases of liver problems, kidney damage, seizures, coma, and deaths. Pennyroyal oil should not be swallowed or used anywhere inside the body.

Herbal products such as pennyroyal naturally contain many different chemicals. The amount of each chemical in different products may vary. Some, none, or all of these chemicals may have effects on the body. These effects may change depending on how much of each chemical is found in the specific product.

How should I store pennyroyal?

You should store pennyroyal according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of pennyroyal?

The most common side effects of pennyroyal are listed below. These side effects may vary depending on the amount or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea or vomiting
  • Stomach pain

There may be other side effects of pennyroyal that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of pennyroyal?

While less common, the most serious side effects of pennyroyal are described below, along with what to do if they happen.

Severe Allergic Reactions. Pennyroyal may cause allergic reactions, which can be serious. Stop using pennyroyal and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the hands, face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Skin rash, itching, blisters, or peeling
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Liver Damage. Liver damage, also called hepatotoxicity, can happen when using pennyroyal and may be life threatening. Get emergency medical help right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish (also called jaundice)

Seizures and Brain Injury. Pennyroyal can cause serious damage to the brain and nervous system. Get emergency medical help right away if you have any of the following symptoms after using pennyroyal.

  • Seizures
  • Confusion or changes in mental status
  • Loss of consciousness

Warnings & Precautions

Who should not use pennyroyal?

Allergies to Ingredients. People who are allergic to any of the following should not use pennyroyal.

  • Mosquito plant
  • Pennyroyal
  • Pudding grass
  • Squawbalm
  • Squawmint
  • Tickweed
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific pennyroyal products they stock.

Pregnancy. People who are pregnant or who may be pregnant should not use pennyroyal. See the Pregnancy section below for details.

What should I know about pennyroyal before using it?

Pennyroyal is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are using, or use it as recommended by your health care provider.

Keep pennyroyal out of the reach of children.

Pennyroyal is available in different forms, including an essential oil, dried leaves, teas, and extracts. The oil is the most concentrated and the most dangerous form. Seek medical help right away if you or someone else has swallowed pennyroyal oil or put it anywhere inside the body, even in small amounts.

Pennyroyal can be mistaken for other mint plants. If you are brewing tea from fresh or dried mint plants, make sure you can correctly identify the plant. Accidental poisoning has occurred when pennyroyal was confused with other types of mint.

Herbal products, such as pennyroyal, naturally contain many different chemicals. The amount of each chemical in a specific pennyroyal product can change for many reasons, including the area where the plant was grown, the weather during growth, the time of year when it was harvested, and the way the plant was processed after being harvested. If you switch to a new bottle or a different brand, you may not have the same effects because of this variability. Talk to your health care provider if you have questions or concerns.

The FDA has not tested pennyroyal products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using pennyroyal?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if pennyroyal is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Liver problems
  • Kidney problems

Pregnancy. Pennyroyal should not be used during pregnancy. It may harm both mother and fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if pennyroyal passes into breastmilk. Because of its possible toxic effects, pennyroyal should not be used while breastfeeding. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does pennyroyal interact with foods or drinks?

There are no known interactions between pennyroyal and foods or drinks.

Drinking alcohol may increase the risk of liver damage from pennyroyal. Alcohol can lower the body’s levels of glutathione, a substance that helps protect the liver. Since pennyroyal also lowers glutathione levels, using both together may make liver damage more likely. Avoid drinking alcohol if you are using pennyroyal.

Does pennyroyal interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

The interactions between pennyroyal and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with pennyroyal is incomplete. Always check with your health care provider before taking pennyroyal with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much pennyroyal?

If you or someone else has used too much pennyroyal or swallowed any amount of pennyroyal oil, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Pennyroyal is available in different forms, including essential oil, dried leaves, and teas. The oil is the most concentrated form, and severe poisoning and deaths have been reported even after small amounts were used. Do not use double or extra amounts of pennyroyal.