Natural Standard assigns a letter grade for indications based on the quality of available scientific evidence (view Grading Rationale). Letter grades have the following meaning:
- Strong scientific evidence for this use; - Good scientific evidence for this use; - Unclear scientific evidence for this use; - Fair scientific evidence against this use (it may not work); - Strong scientific evidence against this use (it likely does not work).
Uses based on scientific evidence Scale

Grading Rationale
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health provider.
Abortifacient (uterus contraction stimulant/abortion inducer)

Folkloric use and several human case reports describe use of the essential oil of pennyroyal to cause abortion. However, it may do so at deadly or toxic doses, making this an unpredictable and dangerous use.
Menstrual flow stimulant (emmenagogue)

Folkloric use and several human case reports describe use of the essential oil of pennyroyal as an emmenagogue (menstrual flow stimulant). However, it may do so at lethal or near-lethal doses, making this action unpredictable and dangerous.

The below uses are based on tradition, scientific theories, or limited study. They have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Acne, antiseptic, anti-spasm, anxiety, asthma, cancer, chest congestion, colds, colic, cough, cramps, diarrhea, digestion, diuretic (increasing urine flow), dizziness, dysentery, fever, flavoring agent, flea control, flu, fragrance (detergents, perfumes, soaps), gallbladder disorders, gas, gout, hallucinations, headache, hysteria, immortality, indigestion, insect repellant, intestinal disorders, itchy eyes, joint problems, kidney disease, leprosy, liver disease, bruises and burns, menstrual irregularities (stimulant, regulator), mouth sores, muscle pain, nosebleeds, pneumonia, potpourri, pregnancy, premenstrual syndrome, preparing the uterus for labor, purifier (water, blood), refrigerant, respiratory ailments, sedative, skin ailments (itching, burning, bruising), snake bites (venomous), stimulant, stomach pain, sunstroke, sweating, syncope, toothache, uterine fibroids, whooping cough.

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Standardization

Standardization involves measuring the amount of certain chemicals in products to try to make different preparations similar to each other. It is not always known if the chemicals being measured are the “active” ingredients. American pennyroyal may contain up to 2% of volatile oil and European pennyroyal may contain up to 1% of volatile oil. Both oils are reported to contain 85% to 92% of the pennyroyal constituent pulegone.

Adults (18 years and older)

Note: No safe dose of pennyroyal has been established. The following doses have been used, but may be toxic.

Extract (1:2): Doses of 20 to 40 milliliters per week of pennyroyal have been used but may be toxic.

Oil: Doses of 0.5 to 3 drops of pennyroyal oil have been used but may be toxic.

Tea/infusion: Based on traditional usage, 1 or 2 cups of tea per day made from 1 to 2 teaspoons of dried leaves per cup of boiling water, steeped for 10 to 15 minutes have been used but may be toxic. Pennyroyal tincture in tea water at doses of 0.25 to 0.5 teaspoonfuls (1.25 to 2.5 milliliters) up to twice daily for treating cough, congestion, and upset stomach, has been used but may be toxic.

Topical: Crushed plant material has been rubbed on the body as an insect repellant. Use of pennyroyal tincture mixed with skin cream and rubbed on the body has also been reported.

Veterinary: Pennyroyal has been used as an herbal flea collar for animals by hanging a bag of pennyroyal from a regular collar or using a pennyroyal garland. Safety and effectiveness of these preparations have not been proven.

Children (under 18 years old)

Pennyroyal is not recommended in children due to lack of scientific study and potential toxicity.

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Allergic reactions to pennyroyal or to its components, including pulegone, may occur, although there are no reliable published reports. Signs of allergy may include rash, itching, or shortness of breath.

Side Effects and Warnings

Pennyroyal herb and volatile oils have been associated with multiple reports of toxicity and adverse effects, including seizures, loss of consciousness, and death. In animals, pennyroyal (taken by mouth or placed on the skin) has been associated with liver, lung, and brain toxicity. Doses greater than 10 milliliters of pennyroyal may be associated with death. Cases of human overdose and death have been reported in infants, children, and adults.

· Pennyroyal oil toxicity may cause nausea, vomiting (sometimes containing blood), abdominal pain, burning in the throat, difficulty swallowing, diarrhea, excessive sweating, chills, fever, headache, ringing in the ears, dizziness, extreme thirst, muscle spasms, restlessness, tremor, excessive talkativeness, hallucinations, agitation, drowsiness, fatigue, confusion, mania, seizures, organ failure (brain, liver, lung, kidney, heart), altered (low or high) heart rate, altered (low or high) blood pressure, slow breathing, coma, loss of consciousness, and death. Typically, the first symptoms of poisoning, from either pennyroyal oil or pennyroyal leaves, occur in the stomach and bowels, and are often apparent soon after ingestion. Symptoms in pennyroyal overdose may mimic that of acetaminophen (Tylenol®) overdose, and the use of N-acetylcysteine (an antidote used for acetaminophen toxicity) treatment may prove beneficial.

Other side effects may include contact dermatitis, rash (when placed on the skin), malaise, lethargy, agitation, abnormal sensations, or change (increase or decrease) in pupil size. There are reports that pennyroyal may cause abortion. Pennyroyal has been used historically as an emmenagogue (menstrual stimulant) and may cause menstrual bleeding. There are reports that large amounts of pennyroyal may be irritating to the urinary tract. Pennyroyal may cause hypoglycemia (low blood sugar), hemolytic anemia (low red blood cell count due to destruction of cells), disseminated intravascular coagulation (widespread abnormal clotting and/or bleeding), and metabolic acidosis.

Pregnancy and Breastfeeding

Pennyroyal is not recommended during pregnancy or breastfeeding, due to the risk of uterine contractions, stimulation of menstruation, and abortion.

Many tinctures contain high levels of alcohol, and should be avoided during pregnancy.

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

In theory, the toxicity of pennyroyal may be increased when combined with acetaminophen (Tylenol®): pennyroyal may lower a liver substance (glutathione), which may increase the risk of acetaminophen toxicity. Based on animal and human cases, pennyroyal may cause increased risk of liver damage caused by other drugs.

Based on animal research, pennyroyal may interfere with the way the body processes certain drugs using the liver’s “cytochrome P450” enzyme system. As a result, the levels of these drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. If you are using any medications, check the package insert and speak with your healthcare provider or pharmacist about possible interactions.

Based on human cases, pennyroyal may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary. Based on animal research, pennyroyal may have antihistamine effects, and may cause increased effects if combined with drugs that have antihistamine action such as diphenhydramine (Benadryl®), fexofenadine (Allegra®), or loratidine (Claritin®).

Many tinctures contain high levels of alcohol, and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).

Interactions with Herbs and Dietary Supplements

Based on animal and human cases, pennyroyal may increase the risk of liver damage when combined with some herbs or supplements. Examples of other herbs that may damage the liver include: Ackee, bee pollen, birch oil, blessed thistle, borage, bush tea, butterbur, chaparral, coltsfoot, comfrey, DHEA, Echinacea purpurea, Echium spp., germander, Heliotropium spp., horse chestnut, Jin-bu-huan (Lycopodium serratum), kava, lobelia, L-tetrahydropalmatine (THP), mate, niacin (vitamin B-3), niacinamide, Paraguay tea, periwinkle, Plantago lanceolata, pride of Madeira, rue, sassafras, scullcap, Senecio spp./groundsel, tansy ragwort, turmeric/curcumin, Tu-san-chi (Gynura segetum), uva ursi, valerian, and white chameleon.

Based on animal research, pennyroyal may interfere with the way the body processes certain herbs or supplements using the liver’s “cytochrome P450” enzyme system. As a result, the levels of these herbs or supplements may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. It may also alter the effects that other herbs or supplements possibly have on the P450 system, such as bloodroot, cat’s claw, chamomile, chaparral, chasteberry, damiana, Echinacea angustifolia, goldenseal, grapefruit juice, licorice, oregano, red clover, St. John’s wort, wild cherry, and yucca. If you are using any medications, check the package insert and speak with your healthcare provider or pharmacist about possible interactions.

Based on human cases, pennyroyal may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Possible examples include: Aloe vera, American ginseng, bilberry, bitter melon, burdock, fenugreek, fish oil, gymnema, horse chestnut seed extract (HCSE), marshmallow, milk thistle, Panax ginseng, rosemary, Siberian ginseng, stinging nettle and white horehound.

Pennyroyal and black cohosh have been taken together to induce abortion, and this combination has been associated with toxicity and death. Pennyroyal and blue cohosh have traditionally been taken together to normalize the menstrual cycle in women. In theory, the combination of the two herbs may act together to increase menstrual flow. Notably, blue cohosh has been associated with multiple dangerous effects including stroke.

Based on human study, pennyroyal may reduce the body’s ability to absorb iron in meals by up to 75%.

This entry was posted on Monday, September 14th, 2009 at 7:32 am and is filed under Herbs, Vitamins & Minerals. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.