Peppermint essence, derived from Mentha piperita, has been traditionally used for respiratory relief, but there is also scientific support for its effects on the bronchial system. The primary active constituent, menthol, acts as a mild bronchodilator and has a cooling effect that can subjectively improve the sensation of airflow in the nasal and bronchial passages. Several clinical studies have investigated menthol's impact on subjective feelings of nasal patency and bronchial comfort, although objective improvements in lung function (such as FEV1) are less consistently demonstrated. Menthol has been shown to activate cold-sensitive TRPM8 receptors, which can produce a sensation of easier breathing, even if actual airway resistance is not markedly changed. Additionally, peppermint oil has mild anti-inflammatory and antispasmodic properties, which may help soothe irritated airways.

However, systematic reviews conclude that while peppermint and menthol can provide some symptomatic relief for coughs and mild bronchial irritation, they should not be considered replacements for evidence-based treatments of more serious respiratory conditions like asthma or COPD. Overall, the use of peppermint essence for bronchial support is justified by both traditional use and modest scientific validation, meriting a mid-range evidence score.