What is Pennyroyal ?
Pennyroyal is also known as pulegium, pudding grass, mosquito plant, squaw mint, and European pennyroyal. It is a perennial herb native to Europe, as well as parts of Asia.
An American species, Hedeoma pulegioides, is closely related and is also used to produce oil, as well as Micromeria fruticosa from Turkey.
Mentha pulegium is derived from the Latin 'puleium regium,' which comes from its ability to destroy 'pulices,' or fleas. In France, it was called 'Pouliot.' Instead of pennyroyal, it was first known as 'hop marjoram' and 'puliall royall,' which pennyroyal is a mispronunciation of. Because of the way the herb grows, it was aptly called 'run by the ground' and 'lurk in ditch' in old England.
The plant features creeping roots common to the Lamiaceae family. It has a smooth, round stalk and blooms with small purple flowers. The fragrant leaves are oval-shaped, greyish-green, and smell like spearmint when rubbed.
The herb can be steam distilled fresh or slightly dried to produce the oil, which is clear to pale yellow. As you might expect, it will have a very fresh, herbaceous, and minty scent.
Pennyroyal oil blends well with citronella (Cymbopogon nardus), geranium (Pelargonium graveolens), rosemary (Rosmarinus officinalis), and sage (Salvia officinalis).
Pennyroyal Essential Oil Uses
Pennyroyal is an herb with a medicinal history almost as long as herbal medicine itself.
Its healing qualities date back to the first century, in the time of Pedanius Dioscorides. In his five-volume work, De Materia Medica, you can find pennyroyal mentioned for a wide variety of ailments, particularly those of women.
Likewise, the Roman naturalist Pliny the Elder described many virtues of the herb during that time as well, such as its ability to purify water.
This particular mint was one of many such herbs that were referred to as 'pot herbs' for their wide deployment in culinary use.
One of the pennyroyal's former names, pudding grass, was from a time when it was mixed with currants, spices, and flour. This was then stuffed into a hog's entrails. It was an old-time stuffing, which at the time was deemed pudding.
Flavoring & Scenting
Pennyroyal is said to resemble spearmint (Mentha spicata) in taste. It has been used throughout history to flavor wine and food, as well as to make herbal teas.
As it also smells like spearmint, it has been used to scent colognes, perfumes, detergents, and soaps. 
Historical Medicinal Uses
Before there were tests to determine the toxicity of a substance, pennyroyal was considered to be one of the most important medicinal herbs.
In Culpepper's The Complete Herbal, he begins the section on the herb by saying, "Pennyroyal is so well known unto all, I mean the common kind, that it needs no description."
He then states the methods in which Dioscorides used the plant:
- Thinning out thick phlegm
- Bringing on menstruation
- Warming any cold part
- Causing vomiting when mixed with water and vinegar
- As an antidote to poisonous bites and stings when mixed with wine
- Mixed with vinegar to awaken those who have fainted
- Dried and burnt to strengthen gums
- Soothes gout
- Made into plaster to remove facial marks
- Soothes itches when used as a wash
- Bruised and mixed with vinegar to clean ulcers
- Eliminates bruises of the eyes and burns on the face
- Calms toothache pain when boiled in wine and mixed with honey and salt
- Used as a wrap to take away joint pain
He goes on to write that Pliny added his own remedies to Dioscorides:
- Mixed with other mints in vinegar and placed under the nose to rouse someone who has fainted
- Ease headaches
- Relieved breast and stomach aches
- Mixed with honey, salt, and vinegar to calm cramps and 'convulsions of the sinews'
- Cough remedy when boiled with milk, as well as healing mouth sores
- Brought about menstruation and abortion when drank in wine
Culpepper further notes that Matthiolus, a doctor in Siena that died in 1577, came up with his own uses for the well-rounded herb:
- A decoction of the herb helps edema and jaundice
- Heals headaches and other issues caused by cold
- Clears eyesight
- Eased burns when applied with barley
- Soothed earaches when applied within
- Gave energy to the lethargic
In a latter part of the book, there is an interesting synopsis of the virtues of this herb:
"Pulegium: Pennyroyal; hot and dry in the third degree; provokes urine, breaks the stone in the reins, strengthens women's backs, provokes the menses, easeth their labour in child-bed, brings away the placenta, stays vomiting, strengthens the brain, breaks wind, and helps the vertigo."
In yet another text, Mother's Remedies: Over One Thousand Tried and Tested Remedies from Mothers of the United States and Canada, there were even more uses for this wonder.
One of the dosing instructions was an infusion of the herb, one ounce to a pint of water steeped but not boiled, that could be used without reserve. The other dose called for 2-5 drops of the oil.
These could be used for:
- Stimulant purposes
- Bringing on sweating
- Menstrual troubles
- Suppressed lochia (the vaginal discharge that occurs after childbirth for a couple days up to six weeks)
- Suppressed menses
- Flatulent colic in children
Aid Drowning 'Victims'
Since it has such a reputation for being an enemy of bugs, it is interesting to note that in another text from days gone by, The Old English Herbals, that pennyroyal had another use.
It stated that the warm ashes of the burnt herb could be used to revive drowning flies and bees. Upon placing them in the ash, "they shall recover their lyfe after a little tyme as by ye space of one houre."
Up until scientists discovered how dangerous the herb was, the answer to 'what is pennyroyal good for?' was: a lot!
Pennyroyal Essential Oil Benefits
The side effects and dangers of using pennyroyal essential oil far outweigh the benefits.
The herb derives its name from its ability to kill fleas and has been used for this and other pests throughout the ages.
The oil is still used to some degree as an insecticide and can be found in some commercial preparations. Unfortunately, you can also find countless recipes online using pennyroyal to keep fleas, ticks, and other insects off of yourself and your pets.
They generally advise a number of pennyroyal essential oil drops in some water with other oils, like peppermint, citronella, and lemongrass. Then you shake and spray on your skin or on your pets and the bugs stay away.
Please do not do this.
While at least some of the recipes I have seen recommend not to do this if you are pregnant, it is wise not to do this at all.
This applies to using the oil on animals as well. There have been reports of animals dying from pennyroyal oil poisoning when well-meaning owners have treated them for fleas with the substance. This goes for both dogs  and cats.
Tisserand recommends a dermal maximum of 1.3% based on a pulegone level of 86.7% with a maximum dermal limit of 1% for that constituent. It is wholly contraindicated during pregnancy due to the hepatotoxic and carcinogenic danger of this naturally-occurring chemical.
As a tea, pennyroyal was used for many things. It was recommended to steep the herb and drink in order to use as a:
- Anthelmintic to expel parasites and worms
- Antispasmodic for cramping and convulsions
- Antitussive to relieve cough
- Carminative to reduce flatulence and abdominal bloating
- Decongestant and expectorant to thin and reduce mucus
- Digestive and stomachic tonic to aid in digestion and relieve stomach issues
- Diaphoretic to induce sweating
- Emmenagogue to induce menses
- Febrifuge to reduce fever
Pennyroyal tea was also applied topically as a(n):
- Antiseptic to clean and heal wounds
- Insect repellant, particularly to keep gnats away from the face
- Refrigerant to cool the body and reduce fever
- Rubefacient to redden the skin as a counter-irritant 
In Mother's Remedies, it was stated that a "...five-cent package can be bought at any drug store."
Side-Effects of Pennyroyal
According to WebMD, there are numerous detrimental effects of using pennyroyal: 
- Kidney, liver, and nervous system damage
- Nausea, vomiting, and abdominal pain
- Burning sensation in the throat
- Hearing and vision problems
- Increased blood pressure
- Liver failure
- Brain damage
They further point out that existing liver or kidney damage could be made worse by ingesting pennyroyal.
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Pennyroyal Essential Oil Research, Facts, and Studies
Food and Drug Administration (FDA)
With all of the danger surrounding pennyroyal, it is interesting to note that the herb, both American and European, is listed on the "Everything Added to Food in the United States" (EAFUC) list. 
Herbal Tea Toxicity in Infants
Two infants were severely hurt, one fatally, after ingesting mint tea. Upon examination, it was determined that the teas contained pennyroyal.
The first infant developed sudden cerebral edema, liver failure, and necrosis. The child tested positive for only menthofuran but died from its injuries.
The second infant tested positive for both pulegone and menthofuran. The baby developed epileptic encephalopathy and hepatic dysfunction but survived. 
Statistics of Self-Induced Abortion Attempts
There are numerous cases throughout history when women have attempted to induce abortion by using pennyroyal in various forms.
1897 In Britain, a 23-year old woman took a tablespoon of pennyroyal oil in order to induce menstruation, which had been absent for six months. She came into the hospital after vomiting for four days.
The doctor, W.T. Allen of the Parish Missionary in Liverpool, treated her with morphia (morphine), and rectal alimentation (nourishment through rectal delivery), which resolved the vomiting. However, her condition continued to deteriorate, and she died eight days after ingestion, on March 19, 1897.
The druggist who had sold the young lady the pennyroyal stated he had never heard of poisoning by the substance in his 30 years of work. 
(c) 1909: A man was convicted after prescribing pennyroyal pills. The woman had a miscarriage and died two months later.
1912: This case also involved pills, which were ingested by a 16-year-old trying to abort her baby. This one was also fatal.
In 1954, there was a case in which a woman swallowed a vial of pennyroyal, purchased another the day after, and drank that as well. She went to her doctor after feeling ill, who prescribed codeine pills.
When she was later admitted to the hospital and it was discovered she had severe vaginal bleeding, she confessed to taking the poison in an effort to induce the abortion of a three-month pregnancy. This was on October 15th. She died on October 28th, after suffering severe liver and kidney damage. 
1961: A 23-year old woman took three pennyroyal tablets 3-4 times a day for four days in an effort to induce abortion. She ended up having epileptic fits, hallucinations, and severe confusion. After a brief hospitalization, she survived and later delivered a daughter. 
1978: An 18-year old ingested two ounces of oil to induce abortion. She died after seven days. 
1994: In this case, it is unclear whether the 24-year-old woman died from complications from an ectopic pregnancy or from pennyroyal poisoning. She had drunk a pennyroyal extract-infused herbal tea prior to her death.
An abstract from 1996 stated that the herb, which is widely available, is an "herbal toxin of public health importance." The authors propose a greater understanding of the toxic mechanism and stricter control of the herb to the general public. 
Treatment for Pennyroyal Toxicity
The antidote for overdoses of pennyroyal is glutathione, which detoxifies the metabolic toxins. In hospital settings, N-acetylcysteine is administered in a similar way as it is for acetaminophen overdose. 
Pennyroyal's claim to fame throughout the years has been as a natural abortifacient. This may be a fallacy, as pointed out by Lise Alschuler, Bastyr University botanical medicine chair:
"Pennyroyal oil has a long folk history as an abortifacient. It isn't really. In most cases, it fails to induce abortion. What women are doing in these cases is creating such high toxicity that their own body is unable to sustain the pregnancy.
... If pennyroyal oil is to work as an abortifacient, it's going to work because it's poisoning the mother."
While the plant has been used for a myriad of ways since the dawn of natural medicine, there is no way to determine a therapeutic dose of this often unreliable plant.
It is advised to stay away from pennyroyal essential oil, especially as the toxic pulegone is concentrated in it.
This is true no matter which pennyroyal you get the oil from, whether it is the European, Turkish or North American type.