About Peppermint Essential Oil
Peppermint essential oil (Mentha x piperita) is distilled from the flowering tops of the plant. It is rich in menthol, which comprises up to half of the oil’s total composition. Peppermint oil also contains menthone, 1,8 cineole, and limonene.
Actions & Indications
Peppermint has a long history of usage in herbal medicine as a digestive aid. In aromatherapy, the oil is diffused to help alleviate headaches and nausea. In aromatic medicine, however, the harsh effects of menthol need to be taken into consideration when determining appropriate use. This is determined by combining known risks outlined in the scientific literature with the studies that show the pharmacological actions of the oil.
Peppermint essential oil’s cooling effects are useful for pain relief. The oil also has antitussive abilities. The scientific literature covers a wide range of uses for peppermint oil. Those with the most significance cover the areas of exercise endurance, intestinal complaints, and as an antimicrobial, particularly against fungal and viral infections. Because peppermint essential oil has such a vast amount of scientific research, the studies outlined below reflect just a sampling of available research.
Laboratory Research Studies
Antimicrobial: Peppermint oil was evaluated for its antiviral activity against herpes type 1 and 2 in a 2003 in vitro study. It was tested against drug resistant strains, which are increasingly common and present difficulties in treatment. The oil profile was consistent with a typical peppermint oil sourced from the US or the France. In this study, it was found to be effective for both types within a 2-3 hour period. What is significant about this study is that the pharmaceutical product used for comparison inhibits viral replication inside the cell, whereas the peppermint oil was found to inhibit it before it enters the cell. Viruses are not technically living beings and can only replicate inside of a cell, so the ability to render it inactive before it enters the cell is extremely promising when it comes to treating resistant infections.
Clinical Research Studies
Endurance: A 2013 study published in the Journal of the International Society of Sports Nutrition describes research conducted to evaluate the potential for supplementation with peppermint oil to enhance athletic endurance. In this small study, 12 participants were given a dose of 0.05mls (approximately 1 average sized drop) of peppermint oil daily for 10 days. On days one and ten, they subjected themselves to a treadmill exercise while researchers monitored their heart rate, gas exchange variables, time to exhaustion, vertical distance, total work, and horizontal distance. This was not a blind or a placebo controlled study, and a control group was not used. The method of evaluation was what is called a pre-test/post-test evaluation, where the exact same test is administered to the same group with a time frame in between each test. The downside of this test is that there is a risk that the participants realize they are being evaluated and choose to spend that time working on improvement in the subject area. However, the close retest at only ten days later helps to reduce that potential, reducing confounding factors.
In this test, there was a significant improvement in the performance of all of the patients. A 40% improvement was seen in horizontal distance and a 52.3% improvement was seen in vertical distance. Time to exhaustion was increased by almost 25%. So, not only were they able to stay on the treadmill longer, the amount of ground they covered in that time increased significantly. Additionally, there was a “substantial increase” in respiratory ventilation, respiratory rate, and lung function. Both resting and exercise heart rates were reduced in the post-test.
The implications of this study are difficult to apply to a larger population due to the small study size and lack of documented information about the GC-MS of the oil used in the study. However, these actions are consistent with what is known about the benefits of peppermint oil. Given the small dose, a single drop per day may be obtained through culinary preparations and it would be reasonable to conclude that athletes may benefit from the addition of whole mint to their diets or a supplement of up to 1 drop a day of mint essential oil in a safe preparation.
Gastric Spasms: Tested during upper endoscopy, the patients who had been given peppermint essential oil internally had a significant reduction in overall gastric spasms compared to the control group. (Kurosaka, et al, 2003) Currently, an anti-spasmodic injection is given to patients undergoing this procedure, and it carries significant side effects. With this success, the study concludes that peppermint oil is preferable thanks to its efficacy and safety in reducing gastric spasms.
Intestinal Complaints: The use of peppermint essential oil with the greatest amount of scientific evidence is the internal consumption of the capsules for intestinal complaints, specifically irritable bowel syndrome (IBS). In addition to conclusive studies on the subject, there are a couple of pharmaceutical products available by prescription in certain European countries that contain peppermint oil for the clinical treatment of IBS.
A 2005 literature review published in the journal Phytomedicine discusses the results of 16 studies on the use of peppermint essential oil, specifically with irritable bowel syndrome, which met inclusion criteria. Ten of the studies were randomized and twelve were placebo controlled. Three studies compared the use of peppermint essential oil with pharmaceutical alternatives. While many of the studies were small in size, the total of all 16 studies represents 661 total trial patients. The range of success with the treatment was 39% to 79%, and adverse events included heartburn and anal burning. However, the pharmaceutical alternative also resulted in adverse events, and the overall conclusion from this review is that peppermint oil is a safe and effective treatment for IBS. In these studies, the dosage ranged in size and the supplement was enteric coated in 15 of the 16 studies.
Enteric coating provides a protective layer that enables the supplement to avoid being broken down in the harsh acidic environment of the stomach. This cannot be replicated at home in gelcaps or through chewables or similar products. Therefore, the applications of these studies are limited in scope due to the inability to replicate the products specifically in a home environment. However, traditional use also supports the consumption of peppermint products as an herbal remedy for digestive complaints, so the use of an after-dinner mint or similar preparation may have some additional benefits beyond simply freshening the breath. To evaluate specifics of non-enteric coated alternatives, further studies are needed.
Original FIW Research
Hypothyroid-Induced Fatigue: The Franklin Institute of Wellness research team studied a peppermint essential oil-based blend of essential oils in a 2016 clinical trial for its effects on fatigue scores of women with hypothyroid disease, including Hashimoto’s Disease. This study found that inhalation of the blend for 15 minutes each afternoon significantly reduced fatigue and increased energy levels for women in the peppermint based blend group.
Peppermint Essential Oil Safety
- The oil should not be applied to the face or chest of babies or small children.
- Medicinal inhalation is contraindicated for children younger than the age of 2. (Note: this does not apply to routine inhalation from skincare products or household products as most personal care products do not produce a medicinal dose.)
- Ingestion for children under the age of 7 should be limited to culinary use such as in a peppermint candy or breath mint.
- The topical use of medicinal doses of peppermint oil can enhance the penetration of other substances.
- Peppermint can lower esophageal sphincter pressure, so ingestion of large culinary doses or medicinal doses are contraindicated for individuals with GERD.
- The internal use of medicinal doses of the oil can slow the absorption of other drugs. A 2011 study outlined the multiple interactions between peppermint oil with pain relievers and in the metabolism of other products. The extent of interactions between peppermint and the metabolism of other drugs is not clear through existing research; more studies are required. Therefore, the precautionary principle states that those who are on prescription medications or who may be taking prescription medications for an upcoming treatment should avoid the use of peppermint oil unless safety has clearly been established
These contraindications are irrespective of essential oil brand or product. Any pure peppermint essential oil will contain a significant amount of menthol, and this naturally occurring substance is responsible for the contraindications outlined above. The risks of peppermint oil with children are not to be taken lightly. The majority of cases of toxicity in infants resulted from homemade products that were administered to young children for respiratory complaints.
Essential oil ingestion (aka aromatic medicine) is not recommended for children younger than the age of 7, those who are pregnant or may become pregnant, those who are breastfeeding, and those with underlying health conditions without advanced training or consultation with someone trained specifically in the science of essential oil ingestion.
Additional Effects: Menthol is often used in over the counter products intended as chest rubs for colds and respiratory complaints. In aromatherapy, peppermint and eucalyptus are often used for the same purpose. However, there are many documented reports of harm linked to the use of menthol. When it is consumed or applied topically, there is a cooling effect upon the body that, according to research conducted in 1996 by Almeida et al., can last for 70 minutes or more in 65% of human subjects tested. Additionally, when menthol was administered to rats, it caused them to seek warmer temperatures. Whether through this effect or menthol’s effect on respiratory function, menthol has been shown to cause children to stop breathing and may cause asphyxiation. Therefore, consumption of the potent oil should be limited to culinary use in susceptible populations and used only as directed by the manufacturer or with caution when preparing homemade products.
Topical Application: For medicinal applications, the EO can be used in a preparation up to 10% with the total application not exceeding 1-2 drops, up to 4-5x per day, indefinitely. Stronger preparations can be used short-term by those with professional training in aromatherapy. Skincare applications require a much smaller dose.
Ingestion: It’s important to emphasize the potency of peppermint essential Uoil when discussing dosages. For example, the pharmaceutical product Colpermin® contains 0.2mls of oil for a single dose. That is the same quantity as approximately 1/25 of a teaspoon or around 4 average sized drops of their standardized oil in an enteric coated capsule, which ensures the product can make it through the acidic environment of the stomach. (This product is available to patients older than 15 years old.) With a variance in commercial oils used for homemade preparations, a safe dose would equal approximately 3 drops of a crude oil sourced from mint grown in France or the US in a capsule, chewable, or other preparation, administered no more than three times a day, putting the daily maximum intake at 9 drops.
LD50: 4.4 g/kg (However, as little as 1 g/kg menthol can be fatal.)
Tips & Notes
Cooking with Peppermint EO: Mint is used in both sweet and savory dishes and can be used in many drinks as well. The fresh herb is rich in essential oil and can safely and reliably be used in the kitchen when mint essential oil is desired. However, mint essential oil can also be used. Due to the potency of the oil, it is recommended at a ratio no greater than 0.5% of the total dish, which is sufficient to provide a powerful mint flavor to sauces or treats.
Methods of Administration: Peppermint essential oil is ideal for medicinal balms, creams, and other topical products for muscle aches, pain, and infections. For serious digestive complaints, consultation with a licensed care provider should be sought, and standardized enteric coated capsules are recommended for safety and efficacy. For home treatments, mint oil should be sourced from the US or the France and should be limited in total use according to the dosing guidelines above. It should never be administered to children and should always be kept out of the reach of children.
Anderson, L. A., & Gross, J. B. (2004). Aromatherapy with peppermint, isopropyl alcohol, or placebo is equally effective in relieving postoperative nausea. Journal of PeriAnesthesia Nursing, 19(1), 29-35.
COLPERMIN is a registered trademark, owned by McNeil Healthcare Ltd (Ireland).
Grigoleit, H-G., Grigoleit, P., (2005). Review: Peppermint oil in irritable bowel syndrome. Phytomedicine. 12: 601-606.
Hiki, N., Kurosaka, H., Tatsutomi, Y., Shimoyama, S., Tsuji, E., Kojima, J., … & Mafune, K. I. (2003). Peppermint oil reduces gastric spasm during upper endoscopy: a randomized, double-blind, double-dummy controlled trial. Gastrointestinal endoscopy, 57(4), 475-482.
Kamatou, G., Vermaak, I., Viljoen, A., Lawrence, B., (2013). Menthol: a simple monoterpene with remarkable biological properties. Phytochemistry, 96:15-25.
Meamarbashi, A., & Rajobi, A., (2013). The effects of peppermint oil on exercise performance. The Journal of the International Society of Sports Nutrition. 10:15
Samojlik, I., Petkovic, S., Mimica-Dukie, N., Bozin, B., (2011). Acute and chronic pretreatment with essential oil of peppermint (mentha x piperita) influences drug effects. Phytotherapy Research, 26: 820-825.
Schuhmacher, A., Reichling, J., & Schnitzler, P., (2003). Virucidal effect of peppermint oil on the enveloped viruses herpes simplex virus type 1 and type 2 in vitro. Phytomedicine, 10: 504-510.