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 for these uses.

Side Effects Of Pennyroyal

  • When taken by mouth: The 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.

Warnings & Precautions

It 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 the 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.

Pennyroyal Dosage

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.


Consult your doctor or pharmacist.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.