Other
Menthol
Menthol is a compound from peppermint and other mint oils that creates a cooling sensation on the skin and mucous membranes.
The route of use changes the question
The pain trial tested a product applied to the skin; the airway trial tested inhalation. Neither supplies an effective oral supplement dose. For digestive symptoms, the separate peppermint-oil evidence includes enteric-coated capsules, designed to release their contents beyond the stomach. 1 2 3