Chronic cough could be caused by two distinct mechanisms; vagal reflexes via acid exposure to the distal esophagus (GERD) and direct exposure of gastric contents to the hypopharynx (LPR). The current GERD diagnostics using MII-pH monitoring and endoscopy focus primarily on pathophysiology on the distal esophagus, but not on the proximity of gastric contents. Patients with LPR may not have abnormal acid exposure to the distal esophagus or mucosal injury, and objective assessment on the proximity of gastric contents using hypopharyngeal multichannel intraluminal impedance (HMII) is therefore crucial to accurately evaluate LPRD-related chronic cough.

Background: Menthol is an ingredient with antitussive properties in over-the-counter medicines. However, only a few studies support the cough-relieving effects of these products. Therefore, we aimed to examine the cough-relieving effects of menthol. Methods: Baseline capsaicin cough sensitivity was measured in healthy adults on day one. Four weeks later, the menthol oral stimulation test was performed. Results: Forty-four individuals participated in this study. Median capsaicin threshold concentration of control and menthol were 7.81 μM and 15.63 μM, respectively. Cough thresholds were increased by oral menthol stimulation. Conclusions: Oral administration of menthol suppressed capsaicin cough sensitivity in healthy adults.