Because the skin on the face is rather sensitive, and the eyes are close-by, a 10% dilution of essential oil is a good balance of safety and efficacy. Direct contact with the delicate membranes, such as inside the nasal passages, should be avoided as it can cause a temporary burning sensation. Peppermint oil should not be used with children under two years of age; instead, Spearmint oil, peppermint's milder, sweeter cousin, is an excellent choice.
1 Battaglia, Salvatore. The Complete Guide to Aromatherapy. International Centre of Holystic Aromatherapy, 2003.
2 Rhind, Jennifer Peace, and David Pirie. Essential Oils: A Handbook for Aromatherapy Practice. Singing Dragon, 2012.
3 Moss, Mark, et al. “Acute Consumption of Peppermint and Chamomile Teas Produce Contrasting Effects on Cognition and Mood in Healthy Young Adults.” Plant Science Today, vol. 3, no. 3, Sept. 2016, pp. 327–336., doi:10.14719/pst.2016.3.3.246.
4 Göbel H, et al., “Effectiveness of Oleum Menthae piperitae and Paracetamol in Therapy of Headache of the Tension Type”. Nervenarzt. vol.67, no. 8, Aug. 1996, pp. 672-681., doi:10.1007/s001150050040. PMID: 8805113.
5 Shams, Rouzbeh, et al. “Peppermint Oil: Clinical Uses in the Treatment of Gastrointestinal Diseases.” JSM Gastroenterology and Hepatology, vol. 3, no. 1, 19 Jan. 2015, pp. 1035–1046.
6 Samarth, R M and Kumar, Ashok. “Mentha piperita (Linn .) Leaf Extract Provides Protection Against Radiation Induced Chromosomal Damage in Bone Marrow of Mice.” Indian Journal of Experimental Biology, vol. 41, no. 3, Mar. 2003.
7 Sharma, Ambika, et al. “Protective Effect of Mentha Piperita Against Arsenic-Induced Toxicity in Liver of Swiss Albino Mice.” Basic & Clinical Pharmacology & Toxicology, vol. 100, no. 4, Apr. 2007, pp. 249–257., doi:10.1111/j.1742-7843.2006.00030.x.
8 Herrmann, E C and Kucera, L S. “Antiviral Substances in Plants of the Mint Family (Labiatae). III. Peppermint (Mentha Piperita) and Other Mint Plants.” Experimental Biology and Medicine, vol. 124, no. 3, 1 Mar. 1967, pp. 874–878., doi:10.3181/00379727-124-31874.
9 Okmen, Ahmet Sadan, et al. “Antibacterial Activities of Mentha Piperita L. Extracts Against Bacteria Isolated from Soccer Player’s Shoes and Its Antioxidant Activities.” Indian Journal of Pharmaceutical Education and Research, vol. 51, no. 3, 2017, pp. S163–S169., doi:10.5530/ijper.51.3s.5.