Pennyroyal Uses and Precautions

Photo caption: Mentha pulegium of the Lamiaceae Family

I wanted to dedicate some time to bring forth an especially ‘royal’ member of the mint family—the pennyroyal plant. The pennyroyal plant is a perennial herb with lilac flowers, historically used to make tea and tincture. Pennyroyal uses also include commercially processed pennyroyal capsules and the extraction of pennyroyal oil from compressed plants. You can purchase pennyroyal plant seeds from herbal markets for gardening purposes too.

So, what’s so important about the pennyroyal plant? What is pennyroyal anyway, and what should you know about this hidden gem of the mint family?

Of all the plants and flowers that are edible, the pennyroyal is an enigma. Most pennyroyal uses are practical, but at the same time, some people fear the pennyroyal plant for certain characteristics. You could say that the pennyroyal plant has a bad reputation, but if you get past it, you can find great pennyroyal uses that make it worth a second visit. Like all plants, I feel it’s essential to scientifically consider all naturopathic applications and get a clear-cut understanding of the benefits and harm it can cause.

Exploring the History of the Pennyroyal Plant

Historical documentation tells us that ancient Greek and Roman cuisines included dried pennyroyal leaves as an herb to add a minty flavor to food. In Medieval Europe, cooks used pennyroyal leaves as a flavor for pudding.

In the 13th century, pennyroyal uses expanded when the leaves of the pennyroyal herb were hand-ground into a paste by mortar and pestle and used by midwives and pregnant women to induce abortions. The pennyroyal plant has strong effects on the body and can effectively increase blood circulation to the extent that it can expel the fetus if used early in pregnancy.

When Virginia became an English colony, people widely used pennyroyal as a common household natural insect-repellant. To this day, insect deterrent is one of the well-known pennyroyal uses. Later, pennyroyal tea became a part of homeopathy for treating several ailments such as tuberculosis and smallpox when these became widespread in North America.

The Taxonomy of the Pennyroyal Plant

Kingdom: Plantae

Clade: Angiosperms

Clade: Eudicots

Clade: Asterids

Order: Lamiales

Family: Lamiaceae

Genus: Mentha

Species: M. pulegium

Binomial name: Mentha pulegium

The pennyroyal plant is native to Europe, and its botanical nomenclature is Mentha pulegium. It is a flowering herb of the Lamiaceae family and is currently found in Europe, North Africa, and the Middle East.

Scientific Background on Pennyroyal Uses

Among pennyroyal uses, bug repellent is a favorite and one of the most effective. Pennyroyal’s popularity for efficiently repelling pests throughout history seems to originate from its minty smell, a typical feature of most plants in the mint family.

According to evolutionary studies, it seems that the plants belonging to the mint family developed their characteristic smell to repel insects and prevent them from ravaging their leaves. Through evolutionary adaptation, mint plants, including the pennyroyal plant, produce a molecule with a minty smell. The molecule blocks the receptors in the antennae of insects, disturbing their navigation senses and preventing them from locating the plant.

Pennyroyal releases these minty-smelling molecules to make the insects feel disoriented, unsafe and to repel them, therefore, saving the plant from being eaten. This same quality makes the pennyroyal plant perfect for human use; it’s a marvelous natural insect-repellent and can keep your pets and homes free from annoying pests!

Uses of Pennyroyal

If you’ve grown the pennyroyal plant in your garden, it smells great. Like other mint plants, It can be a tremendous chemical-free natural insect-repellant and is a perfect choice for those who like a natural solution.

Even though pennyroyal is not a popular member of the mint family today, it’s a tremendously helpful flowering herb. People have been discovering pennyroyal uses for dried leaves and oil for ages.

Historically, people primarily used pennyroyal in culinary flavoring, household medicine, insect-repellant, and emmenagogue (to induce menstruation) among the Greeks, Romans, and Europeans. Today we may only rely on it for insect repellent, but we can also use it for scent. Even though this miraculous plant is misunderstood, it can be a fantastic additive in aromatherapy. However, you should handle it very carefully. Ingestion of the pennyroyal plant is highly toxic and can lead to the malfunctioning of the liver and uterus.

Below is a list of the traditional and currently common pennyroyal uses and applications

•   Insect Repellant

I use pennyroyal essential oil to prevent mosquito bites. We have plenty of mosquitoes here, and I can brag about my success in keeping them away with this trick. I wear a few drops of the pennyroyal plant oil in a necklace diffuser, and it is quite convenient this way.

However, I would advise against rubbing the pennyroyal oil directly on the skin as it is a potent toxin if it somehow finds its way inside your body, even in small amounts. To use it safely close to your body, I recommend using it in an essential oil necklace diffuser to prevent direct absorption through your skin. You can check out our craft brand Eupterrae for superb high-quality, beautiful necklace diffuser craft ideas!

•   Aromatherapy

Pennyroyal oil has a powerful smell of mint. You can add it to your aromatherapy oil to clear your cold or flu. You can also mix it with diffuser oil to make your room smell clean and fresh. Here is a list of the pennyroyal essential oils I recommend for those wishing to add this uncommon mint to their home and living. But, again—use caution whenever handling pennyroyal oil.

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•   Pest Control

Among the top pennyroyal uses is for keeping pests out of your house. You can rub a little pennyroyal essential oil on the exterior portion of your doors, on the outer surfaces of windows (if it is a latch type), and also on open fireplaces (not gas-lit ones). The pungent smell of mint from the pennyroyal oil disrupts the senses of the insects’ antennae. Their numbed antennae make them feel unsafe, confused and make them instinctively back off from the area.

Using pennyroyal is super-effective in keeping hibernating bugs away during the cool Fall months when they look for a cozy place to spend the winter. It’s suggested to reapply the oil on the exterior surfaces once a month as long as required.

Even though I have used pennyroyal essential oil to remove some annoying fleas that my dog brought home, I would advise you to be extremely cautious about how, where, and how much you use it, as pennyroyal is highly toxic to animals and humans alike. I recommend its usage only in places or things where no person or pet can risk licking or accidentally ingesting it. If you plan to use it as a flea-repellent for your pet, I suggest you dab it along the animal’s back so that they cannot reach it however hard they try. With this mode of application, pennyroyal can keep those ticks and fleas at bay (offering a more natural solution than traditional flea and tick preventatives).

•   Teas and Tinctures

Pennyroyal was used in tinctures to cure a cold for several centuries for its efficacy in reducing fevers and headaches. Pennyroyal uses also include treating indigestion, flatulence, and other problems with the digestive tract. Pennyroyal has been a popular trend in weight loss due to its slimming properties. The ‘royal’ comes from the special status among the mint family because of all its health benefits.

Pennyroyal leaves were used to make tinctures to prevent infection and as an antidote to food poisoning. It was used as a detox because of its unique ability to treat the urinary tract, kidneys, and uterus. However, with the observations over time, its high toxicity makes the internal antiseptic property of pennyroyal quite questionable.

A Word of Caution When Using Pennyroyal

Pennyroyal has been famously used in the past centuries to stimulate menstruation and to induce abortions. It was mostly consumed as a tea or, sometimes, people directly ingested the oil. However, this is NOT RECOMMENDED, as there have been multiple deaths due to overdose of the pennyroyal oil. Regarding the usage of the pennyroyal oil by ingestion, I certainly recommend against it. I would suggest using it in only the three safe ways listed above (insect repellent, aromatherapy, and pest control).  I have not come across any measured safe dosage for this oil’s internal use.

Tips for Growing the Pennyroyal Plant

If you would like to have access to the pennyroyal herb whenever you want, the best way is to grow it in your garden or lawn. Pennyroyal is a beautiful trailing herb that can be grown in hanging baskets or the edges of your garden, especially the European breed. The American variety of pennyroyal can be grown both indoors and outside, making gardening yet another of pennyroyal’s uses. They are very easy to propagate from their seeds and can be further propagated by dividing the grown plants or through stalk cuttings.

If you are planning to propagate the pennyroyal seed, it will require ample light for germination but once germinated, it will grow quite fast. The best growing conditions for the pennyroyal plants are the prepared garden beds after the last frost of the winter. You can plant the seeds about 1 inch beneath the surface and keep the top layer moist to aid germination. It takes about two weeks for the sprouts to appear.

If you want to grow them by dividing, don’t split them more than once every three years. Instead, do it in early spring to get good growth.

Quick tip: Frequent pinching of the ends of the growing pennyroyal plant stimulates it to grow in the shape of a compact bush.

Final Note on Pennyroyal Uses

If I were to present my personal opinion on pennyroyal, I would say that I feel it is a highly intriguing member of the mint family plants. Its strong scent and its widespread use in history make it unforgettable. At my home, I have made it a point to carry pennyroyal essential oil in my medicine cabinet since I discovered it during my ethnobotany classes in college. It has been exceptionally useful at times. Pennyroyal might be perfect for you if you wish to use long-lasting natural replacements for everyday household things such as bug sprays or flea collars.

For those wishing to gain in-depth knowledge of essential oils, I recommend

Ancient Medicine section.