Cough: Causes and symptoms

In the majority of cases, coughs are caused by respiratory infections, including:

• colds or influenza, the most common causes of coughs
• bronchitis, an inflammation of the mucous membranes of the bronchial tubes
• croup, a viral inflammation of the larynx, windpipe, and bronchial passages that produces a bark-like cough in children
• whooping cough, a bacterial infection accompanied by the high-pitched cough for which it is named
• pneumonia, a potentially serious bacterial infection that produces discolored or bloody mucus
• tuberculosis, another serious bacterial infection that produces bloody sputum
• fungal infections, such as aspergillosis, histoplasmosis, and cryptococcoses

Environmental pollutants, such as cigarette smoke, dust, or smog, can also cause a cough. In the case of cigarette smokers, the nicotine present in the smoke paralyzes the hairs (cilia) that regularly flush mucus from the respiratory system. The mucus then builds up, forcing the body to removed it by coughing. Post-nasal drip, the irritating trickle of mucus from the nasal passages into the throat caused by allergies or sinusitis, can also result in a cough. Some chronic conditions, such as asthma, chronic bronchitis, emphysema, and cystic fibrosis, are characterized in part by a cough. A condition in which stomach acid backs up into the esophagus (gastroesophageal reflux) can cause coughing, especially when a person is lying down. A cough can also be a side-effect of medications that are administered via an inhaler. It can also be a side-effect of beta-blockers and ACE inhibitors, which are drugs used for treating high blood pressure.

— Jeffrey P. Larson, RPT