The membranes of the nose and throat are tough, but they can be injured by many things including nasal sprays and nose drops and various medications when used to excess. A deformed nasal septum may also interfere with the normal exchange of air. So will inflammation of the sinuses or sinusitis. All such conditions should be corrected as soon as possible, for breathing is most important to health.

The trouble does not always stop in the nose and throat. Often it extends down to the larynx or voice box, causing hoarseness or laryngitis.  From there it may descend into the lower respiratory tract, causing bronchitis and perhaps even pneumonia.