Pennyroyal is a plant. The leaves, and the oil they contain, are used to make medicine.

Despite serious safety concerns, pennyroyal is used for the common cold, pneumonia, fatigue, ending a pregnancy (abortion), and as an insect repellant, but there is no good scientific evidence to support these uses.

In manufacturing, pennyroyal oil is used as a dog and cat flea repellent, and as a fragrance for detergents, perfumes, and soaps.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for PENNYROYAL are as follows:

Insufficient evidence to rate effectiveness for…

• Ending a pregnancy (abortion).
• Canker sores.
• Common cold.
• Indigestion (dyspepsia).
• Fatigue.
• Gas (flatulence).
• Gallbladder disease.
• Gout.
• Insect repellant.
• Liver disease.
• Mosquito repellant.
• Pain.
• Pneumonia.
• Stomach pain.
• Other conditions.

More evidence is needed to rate the effectiveness of pennyroyal for these uses.

When taken by mouth: Pennyroyal oil is LIKELY UNSAFE. It can cause serious liver and kidney damage, as well as nervous system damage. Other side effects include stomach pain, nausea, vomiting, burning of the throat, fever, confusion, restlessness, seizures, dizziness, vision and hearing problems, high blood pressure, lung failure, and death. There isn’t enough reliable information to know if pennyroyal is safe to use as a tea.

When applied to the skin: Pennyroyal oil is LIKELY UNSAFE when applied to the skin.

Special precautions & warnings:

Pennyroyal is LIKELY UNSAFE for anyone to use, but it is especially unsafe for people with the following conditions.

Pregnancy and breast-feeding: It is LIKELY UNSAFE to take pennyroyal by mouth or apply it to your skin when pregnant or breast-feeding. There is some evidence that pennyroyal oil can cause abortions by causing the uterus to contract. But the dose needed in order to cause an abortion could kill the mother or cause life-long kidney and liver damage.

Children: It is LIKELY UNSAFE to give children pennyroyal by mouth. Infants have developed serious liver and nervous system injuries, or even death, after taking pennyroyal.

Kidney disease: The oil in pennyroyal can damage the kidney and make existing kidney disease worse.

Liver disease: The oil in pennyroyal can cause liver damage and might make existing liver disease worse.

Moderate

Be cautious with this combination.

Acetaminophen (Tylenol, others)

Pennyroyal can cause liver damage. Taking pennyroyal with acetaminophen, which can also cause liver damage, might increase the risk for liver damage.

Iron

Pennyroyal might reduce the absorption of iron from supplements.

Iron-containing foods

Pennyroyal might reduce the absorption of iron from foods.

The appropriate dose of pennyroyal depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for pennyroyal. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

American Pennyroyal, Dictame de Virginie, European Pennyroyal, Feuille de Menthe Pouliot, Frétillet, Hedeoma pulegioides, Herbe aux Puces, Herbe de Saint-Laurent, Huile de Menthe Pouliot, Lurk-In-The-Ditch, Melissa pulegioides, Mentha pulegium, Menthe Pouliot, Menthe Pouliote, Mosquito Plant, Penny Royal, Pennyroyal Leaf, Pennyroyal Oil, Piliolerial, Poleo, Pouliot, Pouliot Royal, Pudding Grass, Pulegium, Pulegium vulgare, Run-By-The-Ground, Squaw Balm, Squawmint, Stinking Balm, Tickweed.

To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.

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