Scientists from the School of Medicine at the Iranian Shiraz University praised the popular essential oil of peppermint, listing its actions as “antiviral, antibacterial, antifungal, antibiofilm formation, radioprotective [protective against the harmful effects of radiation], antioedema [edema: fluid buildup in tissues], analgesic, [with] antioxidant activity.”1
The authors of the December 2012 study then explained that in the past 20 years, resistance to antifungal drugs has dramatically accelerated, particularly the azole class of drugs. They write that “Azole-resistant Candida and Aspergillus species are the top pathogens responsible for nosocomial [hospital-acquired now referred to as healthcare associated] or food-borne infections.”2 The U.S. Centers for Disease Control report an estimated 1.7 million healthcare-associated infections (HAI) from all types of microorganisms cause or contribute to 99,000 deaths each year.3

In addition, the scientists report that “the formation of biofilms by Candida species [has] raised concerns due to their increased resistance to antifungal therapy,” which protects “the microbial cells within biofilms from the host immune defenses.”4

Because peppermint essential oil (Mentha piperita) has been shown to inhibit fungal growth and aflatoxin production of Aspergillus species, it was tested against 25 standard strains of fungi, including Candida albicans, C. tropicalis, C. krusei, C. glabrata, C. dubliniensis, Aspergillus flavus, A. fumigatus, and A. oryzae. Additionally, peppermint essential oil was tested against 35 clinical isolates of yeasts, including “Cryptococcus neoformance [correct spelling is neoformans] . . . a well-known primarily opportunistic pathogen which produces chronic and life-threatening meningitis.”5

The study concludes that “The EO [peppermint] inhibited the growth of all of the tested yeasts at concentrations of 0.12-4?L/mL. No significant differences in inhibitory concentrations were found between azole-resistant and -susceptible strains.”6 In addition, the EO killed the standard strain of Cryptococcus neoformans at a concentration of 4?L/mL.

The study also reports that since Mentha piperita exhibited similar antifungal effects against the azole-resistant and azole-susceptible strains, it can be assumed that peppermint’s mode of action is different than the antifungal drug.

Also, the researchers note that the most common Candida species that forms biofilms isC. albicans, and the Iranian study shows the biofilm formation was completely inhibited by peppermint essential oil. The entire study is available free at PubMed at ISRN.PHARMACEUTICS2012-718645.pdf.

One would have to agree with these scientists who state that “EO of M. piperita with potential active antimicrobial properties might be considered as a natural source for the maintenance or extension of the shelf life of products . . . [peppermint] might also be considered for developing products for controlling fungal infections.”7


  1. Saharkhiz MJ, et al., “Chemical Composition, Antifungal and Antibiofilm Activities of the Essential Oil of Mentha piperita L.,” ISRN Pharm. 2012;2012:718645. Epub 2012 Dec. 13.
  2. Ibid.
  4. Saharkhiz, op cited.
  5. Ibid.
  6. Ibid.
  7. Ibid.