Pennyroyal (Mentha pulegium, Lamiaceae) is a creeping, perennial herb with small lavender flowers and aromatic, glossy, gray-green, oval leaves, growing to about 16 inches with fibrous roots.1,2 The herb is native to Europe and Asia, mainly Morocco, Tunisia, Portugal, Italy, Turkey, and Spain.1 Various varieties exist, including the "recta" and "decumbent" which are found in Great Britain. Pennyroyal's traditional usage extends to ancient times and includes a wide variety of ailments. It was thought to be a blood purifier and to enhance the purification of water. Water infused with pennyroyal leaves was given to calm spasmodic and nervous dispositions and was used against cold and joint inflammations. The Latin pulegium is derived from pulex meaning flea, as the herb was used to repel fleas.2 In Iranian traditional medicine, pennyroyal is used to treat gastrointestinal disorders including dyspepsia, nausea, vomiting, bloating, stomachache, infection, and diarrhea.3
The modern British Pharmacopoeia states that pennyroyal is useful for treating the common cold, gout, delayed menstruation, and digestive ailments such as flatulent dyspepsia and intestinal colic.1 Therapeutic actions include stimulant, antiseptic, insect repellent, antispasmodic, digestive, and refrigerant. The essential oil contains a large amount of pulegone, which is abortifacient and can be toxic, especially to the liver and nervous system. Other constituents include menthone, piperitenone, and octanol.
A randomized, double-blind, placebo-controlled, parallel group clinical trial conducted in Iran from December 21, 2015 to March 19, 2016 sought to evaluate the efficacy of adjunct pennyroyal in treating functional dyspepsia as an adjuvant treatment.3 Researchers determined that 330 mg pennyroyal extract given three times per day for two months, along with 40 mg famotine, significantly reduced the severity of dyspeptic symptoms, improved quality of life, and decreased H. pylori infection in patients with functional dyspepsia compared to those taking famotine alone.
Pennyroyal should not be used long term and should not be confused with the native North American pennyroyal (Hedeoma pulegioides, Lamiaceae).1,2
1Lawless J. The Encyclopedia of Essential Oils. San Francisco, CA: Conari Press; 2013.
2Tucker AO, DeBaggo T. The Encyclopedia of Herbs – A Comprehensive Reference to Herbs of Flavor and Fragrance. Portland, OR: Timber Press; 2009.3Khonche A, Huseini HF, H Abdi, Mohtashami R, Nabati F, Kianbakht S. Efficacy of Mentha pulegium extract in the treatment of functional dyspepsia: A randomized double-blind placebo-controlled clinical trial. J Ethnopharmacol. 2017;206:267-273.