Menthol oil, derived from peppermint, is commonly used to alleviate symptoms of congestion, especially in the context of colds or respiratory discomfort. The primary mechanism involves menthol’s ability to activate cold-sensitive TRPM8 receptors in the nose and upper airways, creating a sensation of improved airflow and easier breathing. Several small clinical studies and systematic reviews have demonstrated that, although menthol does not actually decongest the airways or reduce mucus, it provides a subjective feeling of relief from nasal congestion. This sensation can help patients feel more comfortable, even if objective measures of airflow are unchanged.

Historically, menthol has been included in many over-the-counter vapor rubs and inhalants for respiratory symptoms, and its use in this context is supported by both longstanding tradition and some scientific investigation. However, the overall quality of evidence is modest: systematic reviews (such as those by Eccles et al., 2013) have found that while menthol improves subjective feelings of congestion, it does not have a significant effect on actual lung function or mucus clearance. Thus, menthol oil’s use for lung congestion is "scientific" in the sense that its effects have been studied and documented, but its efficacy is primarily in symptom relief rather than treating the underlying congestion.