Abstract
Background
Dyspnea is a symptom that can cause significant burden on activities of daily living. Overall, dyspnea has associations with increasing age, high body mass index (BMI), female sex and cardiorespiratory diseases. Aside from pharmacological treatments for underlying cardiorespiratory conditions that cause dyspnea, menthol has been discussed as a potential non-pharmacological intervention. However, its role remains contentious with uncertainty regarding efficacy and potential harm. Thus, this systematic review aims to explore the impact of menthol on dyspnea.Methods
A comprehensive search of databases (MEDLINE, Embase, Cochrane Library) was performed from inception of each database to June 2026. Appropriate randomized controlled trials (RCTs) investigating the effects of menthol on dyspnea outcomes were identified based on strict inclusion criteria. The RCTs included patients with dyspnea from underlying respiratory conditions and lab-based studies that simulated dyspnea in people with no underlying lung pathology through exercise. Studies with patients with respiratory conditions also induced dyspnea through exercise and inspiratory loaded breathing. The primary outcome was dyspnea which was measured through scores like Borg and Multidimensional Dyspnea Profile (MDP). Secondary outcomes included adverse events identified and impact on physiological parameters. Subsequently a descriptive analysis of data was carried out.Results
All eight studies selected showed improvement in dyspnea scores. Four studies positively impacted the immediate perception and sensory qualities domains of the MDP, while one study using a visual analogue scale score decreased dyspnea scores by 42% in one subgroup (flow-resistive loading) and 19% in another (elastic loading). Four studies used the modified Borg score to report dyspnea. Amongst these, Kanezaki et al [12] demonstrated a reduction in score by - 2 at maximal time and - 1 with maximal inspiratory resistive load showing a minimal clinical important difference in dyspnea (MCID). Prieur et al. [16]; Schaeffer et al. [14] and Vanden Bossche et al. [21] reduced Borg scores by 0.3, 0.7, 0.67 respectively but did not reach the MCID. However, all three studies did have participants that showed MCID. One study used the 11-point feeling scale to measure breathing comfort and showcased 1.5-point increase in bre̲athing comfort with menthol ingestion and 1 point increase in comfort with menthol rinse. There were no significant documented negative implications of menthol. Menthol had no impact on forced expiratory volume in one second and airway resistance measures.Conclusion
Menthol is an effective and safe treatment option for the short-term and symptomatic relief of dyspnea both at rest and during exercise.