Overview
Mint oil, most often extracted from the leaves of Mentha piperita, is on the FDA’s GRAS–Generally Regarded As Safe–list. It can, however, cause some adverse effects when used at high doses, according to NYU’s Langone Medical Center.
Toxic Compounds
Mint oil’s primary constituent, menthol, is toxic to humans in high doses when ingested, and dangerous when inhaled by infants. Scientists have also evaluated other substances in mint oil for toxicity, notably menthone and pulegone. Menthone shows some toxic effects on rats at high doses. Pulegone may increase the absorption of other substances through the skin, according to a report by the Cosmetic Ingredient Review Expert Panel on the safety of peppermint oil in cosmetics.
Effects
Mint oil relaxes the smooth muscles, including those in the respiratory tract. Applying mint oil to the face or head of infants can cause severe breathing problems or apnea. Mint oil may also cause severe jaundice in infants with G6PD deficiency. In adults, high doses of mint oil can cause nausea, loss of appetite, loss of balance, heart problems, kidney failure and death. It may also increase reflux in people who have GERD–gastroesophageal reflux disease.
Potential as Insecticide
Mint oil shows promise as a natural insecticide/pesticide alternative. In a study conducted at Auburn University in 2001, cockroaches sprayed with 100 percent mint oil were dead in just over an hour. Treatment with 3 percent mint oil killed cockroaches in a little over four hours.
Animal Studies
Rats given high doses of peppermint oil showed liver damage and brain damage in a series of experiments conducted in the 1980s. Further studies using substances isolated from mint oil showed that rats fed menthol and pulgeone showed weight loss, brain damage and liver damage at doses higher than 20 mg per kilogram of body weight for pulgeone and 200 mg per kilogram of body weight for menthol. The effects of peppermint oil in high doses include muscle weakness, brain damage and seizures.
Toxic Doses
Menthol, the primary constituent of peppermint oil, is toxic to adults in doses of 1 gram per kilogram of body weight, according to a monograph at Natural Standard, an international research organization that focuses on integrative medicine.
About this Author
Since 2001, Deb Powers has been using the knowledge collected over fifty years to write how-to guides and informational articles about a wide variety of subjects. Deb has ghost-written more than a dozen informational e-books on subjects ranging from financial advice to bullying prevention. Her poetry has appeared in “The Astrophysicist’s Tango Partner Speaks”, “The Ballard Street Poetry Journal” and “The November 3rd Club”.
