Both the oil and the extract can have antimicrobial properties, but they can also have an irritating, sensitizing effect on skin.  Peppermint oil is a more potent irritant than peppermint water. Peppermint is a common cause of allergic contact dermatitis on the face, particularly around the mouth, as it’s frequently used as flavoring in toothpastes. [2,3]
- Iscan G, Kirimer N, Kürkcüoglu M, Baser K, Demirci F. Antimicrobial screening of Mentha piperita essential oils. J Agric Food Chem. 2002;50(14):3973-6.
- Posadzki P, Alotaibi A, Ernst E. Adverse effects of aromatherapy: a systematic review of case reports and case series. Int J Risk Saf Med. 2012;24(3):147-61.
- Herro E, Jacob S. Mentha piperita (Peppermint). Dermatitis. 2010;21(6):327-29.