Marshmallow have an antitussive effect by reducing oral and pharyngeal irritation. It alleviates dry cough by:
The information of a protective layer on the inflamed or damaged mucosa of the mouth and throat (up to the larynx)
Increasing the barrier to irritants which reduces the sensitivity of the cough receptors
Since antiquity Marshmallow is considered as a soothing plant for cough. The mucilage contained in the marshmallow enwrap the cough receptors in the throat, alleviate mucosal irritation and thereby reduce the urge to cough.