Peppermint leaf (Mentha × piperita) has a long history of use in traditional herbal medicine for supporting various aspects of respiratory and digestive health, including the comfort of mucus membranes. Scientifically, peppermint leaves contain menthol and other volatile oils, which have mild anti-inflammatory, antimicrobial, and soothing effects on mucosal tissues. Several studies suggest that inhalation of peppermint oil vapors can help ease symptoms of upper respiratory tract infections, such as congestion and irritation of the mucus membranes, largely due to menthol's local anesthetic and decongestant properties. Additionally, some laboratory and small clinical studies indicate that peppermint preparations may reduce inflammation and microbial load on mucosal surfaces.

However, most clinical research has focused on peppermint oil or extracts rather than the leaf itself, and studies specifically evaluating effects on mucus membranes (such as those of the respiratory tract or oral cavity) are limited in scale and quality. There is moderate evidence for symptom relief (e.g., reduced nasal congestion, soothing sore throats) but less direct evidence that peppermint leaf directly supports the health or function of mucus membranes beyond transient symptom relief. Traditional use and modest scientific data support its role, but more robust, targeted research is needed for higher confidence.