Background: Menthol is a natural herbal compound. Its isomer l-menthol presents the characteristic peppermint scent and is also responsible for the cooling sensation when applied to nasal mucosal surfaces because of stimulation of trigeminal cold receptors. The aim of this study was to assess the effect of menthol inhalation on end-inspiratory nasal mucosa temperature and nasal patency.
Methods: Eighteen healthy volunteers with a mean age of 30 years were enrolled in this study. Objective measurements included the septal mucosal temperature within the nasal valve area by using a miniaturized thermocouple as well as active anterior rhinomanometry before and after inhalation of l-menthol vapor. All subjects completed a visual analog scale (VAS; range, 1-10) evaluating nasal patency before and after menthol.
Results: The mean end-inspiratory mucosal temperature ranged from 27.7 degrees C (+/-4.0) before menthol inhalation to 28.5 degrees C (+/-3.5) after menthol inhalation. There were no statistically significant differences between the temperature values before and after menthol inhalation (p > 0.05). In addition, no statistically significant differences between the rhinomanometric values before and after menthol inhalation were observed. Sixteen of the 18 subjects reported an improvement of nasal breathing after menthol inhalation by means of the VAS.
Conclusion: Menthol inhalation does not have an effect on nasal mucosal temperature and nasal airflow. The subjective impression of an improved nasal airflow supports the fact that menthol leads to a direct stimulation of cold receptors modulating the cool sensation, entailing the subjective feeling of a clear and wide nose.