DOES IT WORK?Pennyroyal is a clear example of a natural remedy that is not safe, writes DONAL O'MATHUNA
PENNYROYAL IS a plant from the mint family which has a strong spearmint odour. The herb was commonly used by the Romans and Greeks in cooking, but became less commonly used as its toxic effects were identified. Pennyroyal tea was traditionally used for many reasons, but most commonly to treat fevers and to relieve cold and flu symptoms.
The main traditional use of pennyroyal has been to stimulate menstrual flow and ease painful menstruation. This led to the herb developing a reputation for causing abortions, even in Roman times. However, no evidence is available to show that pennyroyal is safe or effective when used as an abortifacient.
In addition, since teas and oils made from the herb are of uncertain concentration, toxic side effects are relatively common. Despite this, pennyroyal continues to be readily available. Interest is also maintained by the Nirvana song Pennyroyal Tea which some claim alludes to its use as an abortifacient.
Evidence from studies
Pennyroyal plant material is used to make a tea that has been recommended for many different uses. There are no clinical studies available to support any of these uses. An essential oil can also be distilled from the plant and has been used in aromatherapy.
This oil contains a high concentration of pulegone which is believed to be highly toxic. European varieties of the plant give an oil with 80-94 per cent pulegone, while American varieties usually contain less than 30 per cent.
The oil appears to irritate the uterus, leading to contractions, but is also highly toxic to the liver and kidneys. The oil is also recommended to kill fleas on animals, but it can be absorbed through the skin and has poisoned a number of pets.
The only studies available on pennyroyal are reports from poison control centres on its toxic effects. At least four young women have died in the US after using pennyroyal oil to cause abortions. These women consumed 15ml or more of the oil and generally had serious gastrointestinal problems within a couple of hours.
Liver and kidney failure occurred a few days later, leading to their deaths. Numerous other cases have been reported of moderate or serious toxicity. The symptoms were primarily gastrointestinal, but also included dizziness, seizures and coma. These women usually recovered fully after being treated in hospital.
The dose of oil needed to cause adverse effects is unknown. Toxic effects have occurred after a teaspoonful of pennyroyal oil, and death has occurred after a tablespoonful.
Recommendations
Pennyroyal is a herbal remedy that remains on the market without good evidence to support any of its uses. Apart from the legal and ethical issues regarding abortion, the evidence from case reports is that pennyroyal will cause serious toxicity before it will cause an abortion. Accidental poisonings have also been caused when children have ingested the oil or when animals have absorbed the oil through their skin when it was used as a flea repellent.
Pennyroyal is a clear example of a natural remedy that is not safe. Although some promoters warn about the dangers, particularly of the oil, many fail to point out the lack of credible evidence of its effectiveness.
If there is little or no chance of benefit, any risk of harm makes a remedy not worth taking. Anyone taking pennyroyal tea or oil who has an unusual or uncomfortable reaction should go to the nearest AE and bring along a sample of the remedy.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He authored Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007