Mucus protects, moisturizes, and lubricates mucosal surfaces. A child swirling mucus on his or her tongue has performed an experiment on its biophysical properties and is likely to be equally aware of the potential for dramatic increases in mucus, as with the common cold. However, too much of a good thing may be bad, and mucus hypersecretion may contribute to the pathophysiology of asthma, chronic bronchitis, and cystic fibrosis, as well as sinusitis and otitis media. Copious, hyperviscous mucus may directly obstruct airflow or impair mucociliary clearance. Stagnant mucus likely serves as both a nidus for bacterial colonization and perpetuates chronic infection
