What is it?
Pennyroyal is a very poisonous herbal medicine that can cause liver and kidney damage and even death. There is no safe use for it. It has been used to start a woman's monthly period if she is not pregnant. It can also be used to treat a fever.
Other names for Pennyroyal include: Hedeoma pulegioides, American Pennyroyal, Mosquito Plant, Pudding Grass, Squawmint, Stinking Balm, and Tick-Weed.
Ask your doctor, nurse, or pharmacist if you need more information about this medicine or if any information in this leaflet concerns you.
Tell your doctor if you
- are taking medicine or are allergic to any medicine (prescription or over-the-counter (OTC) or dietary supplement)
- are pregnant or plan to become pregnant while using this medicine
- are breastfeeding
- have any other health problems, such as high blood pressure or heart or blood vessel disease
Talk with your caregiver about how much Pennyroyal you should take. The amount depends on the strength of the medicine and the reason you are taking Pennyroyal. If you are using this medicine without instructions from your caregiver, follow the directions on the medicine bottle. Do not take more medicine or take it more often than the directions tell you to.
To store this medicine:
Keep all medicine locked up and away from children. Store medicine away from heat and direct light. Do not store your medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down and not work the way it should work. Throw away medicine that is out of date or that you do not need. Never share your medicine with others.
Drug and Food Interactions:
Do not take Pennyroyal without talking to your doctor first if you are taking:
- Any medicine that may be damaging to the liver. Common examples are alcohol, acetaminophen (Tylenol(R)), herbs such as comfrey, coltsfoot, germander, kava, skullcap, and valerian. Ask your doctor or pharmacist if your medicine may be damaging to the liver.
- Before taking Pennyroyal, tell your doctor if you are pregnant or breastfeeding
- Pennyroyal should never be taken by mouth and should not be put on the skin. It can cause serious liver and kidney damage, coma, and death (3,4,5)
- Do not take Pennyroyal (especially the oil) during pregnancy. Pennyroyal may cause a miscarriage while Pennyroyal oil has caused death (6)
- Do not give Pennyroyal to children (1)
Stop taking your medicine right away and talk to your doctor if you have any of the following side effects. Your medicine may be causing these symptoms which may mean you are allergic to it.
- Breathing problems or tightness in your throat or chest
- Chest pain
- Skin hives, rash, or itchy or swollen skin
Other Side Effects:
You may have the following side effects, but this medicine may also cause other side effects. Tell your doctor if you have side effects that you think are caused by this medicine.
- Blood clotting problems (you may bleed easier and it could take a long time to stop bleeding) (3)
- Increase in your heart beat and blood pressure (3)
- Seizures (convulsions) (3)
- Hallucinating (a feeling that you are seeing, hearing, or smelling something) (3)
- Upset stomach (4)
1. Fetrow CW & Avila JR: Complementary and Alternative Medicines. Springhouse Corporation, Springhouse, PA; 1999.
2. Newall C, Anderson L & Phillipson J: Herbal Medicines: A Guide for Health-Care Professionals. The Pharmaceutical Press, London, England; 1996.
3. Anon: Pennyroyal. In: DerMarderosian A (ed). The Lawrence Review of Natural Products. Facts and Comparisons, St. Louis, MO; 1998.
4. Anderson IB, Mullen WH, Meeker JE et al: Pennyroyal toxicity: Measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 1996; 124(8):726-734.
5. Gordon WP, Huitric AC, Seth CL et al: The metabolism of the abortifacient terpene, (R)-(+)-pulegone, to a proximate toxin, menthofuran. Drug Metab Dis 1987; 15(5):589-594.
6. Brinker F: Herb Contraindications and Drug Interactions, 2nd ed. Eclectic Institute, Sandy, OR; 1998.
7. Bakerink JA, Gospe SM Jr, Dimand RJ et al: Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants. Pediatrics 1996; 98(5):944-947.
Last Updated: 1/4/2018