How does Althaea officinalis work?

Althaea officinalis extracts may suppress coughing in human trials^[1][2][3][4] because of their antibacterial properties, which have been shown in cell culture (in vitro) experiments.^[5][6][7] In animal studies, extracts from Althaea officinalis have also been shown to suppress the coughing reflex via a direct effect on serotonergic receptors in the nasopharynx (a part of the throat behind the nose).^[8] Extracts from Althaea officinalis can also bind to epithelial cells (a type of cell that lines the airways),^[9][10] produce a protective mucilaginous film of polysaccharides,^[9] and reduce inflammation in many cell types,^[11][12] including macrophages (a type of immune cell involved in defending against pathogens).^[13] Consequently, the cough-suppressing effects of extracts from Althaea officinalis might be the result of reduced airway inflammation. However, these possible mechanisms are speculative. Further high quality randomized controlled trials are needed to bolster the current evidence, and additional mechanistic studies are needed to fully understand how Althaea officinalis supplements might work.