Although the exact mechanism by which menthol exerts its antipruritic and analgesic effects has yet to be determined, the discovery that the TRPM8 is its underlying receptor is proving to be significant, particularly in understanding the cooling effect of the botanical (J. Am. Acad. Dermatol. 2007;57:873-8). There are also indications that menthol has therapeutic potential for melanoma. Specifically, melanoma expresses TRPM8 receptors, the activation of which inhibits melanoma viability. Menthol appears to mediate this response through an influx of extracellular calcium ions (Am. J. Physiol. Cell Physiol. 2008;295:C296-301; Am. J. Physiol. Cell Physiol. 2008;295:C293-5).
Peppermint oil
In 2003, Schuhmacher et al. investigated the virucidal effect of peppermint oil and found that it had a direct effect against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) as well as an acyclovir-resistant HSV-1 strain. The investigators concluded, noting the lipophilic nature of peppermint oil, that it might be an appropriate topical treatment for recurrent herpes outbreaks (Phytomedicine 2003;10:504-10).
Because of its flavor, aroma, and cooling qualities, peppermint oil is used in a wide range of products, including cosmeceuticals, personal hygiene products (e.g., bath preparations, mouthwashes, toothpastes, and topical formulations), foods, pharmaceutical products, and aromatherapy. Topical indications include pruritus, irritation, and inflammation. Peppermint oil can act as a skin sensitizer, though, particularly in impaired and sensitive skin (Dermatitis 2010;21:327-9). Although peppermint oil has been reported to be a sensitizer in isolated cases, peppermint oil 8% was not found to be a sensitizer in a recent test using a maximization protocol and the various forms of peppermint (i.e., oil, extract, leaves, and water) are considered to be safe in cosmetic formulations. In rinse-off products, peppermint oil is used in concentrations up to 3% and up to 0.2% in leave-on formulations (Int. J. Toxicol. 2001;20 Suppl 3:61-73).
Conclusion
Peppermint and menthol, its naturally occurring monocyclic terpene alcohol derivative, have long been used for medical purposes. Contemporary practice and continuing research continue to support various uses of M. piperita in the medical armamentarium, with specific and additional uses continually being found in the dermatologic realm.
Dr. Baumann is chief executive officer of the Baumann Cosmetic & Research Institute in Miami Beach. She founded the cosmetic dermatology center at the University of Miami in 1997. Dr. Baumann wrote the textbook "Cosmetic Dermatology: Principles and Practice" (McGraw-Hill, April 2002), and a book for consumers, "The Skin Type Solution" (Bantam, 2006). She has contributed to the Cosmeceutical Critique column in Skin & Allergy News since January 2001 and joined the editorial advisory board in 2004. Dr. Baumann has received funding for clinical grants from Allergan, Aveeno, Avon Products, Galderma, Mary Kay, Medicis Pharmaceuticals, Neutrogena, Philosophy, Stiefel, Topix Pharmaceuticals, and Unilever.