Chronic Cough

Some common causes of chronic cough include asthma, allergic rhinitis, sinus problems (for example sinus infection), and esophageal reflux of stomach contents. In rare occasions, chronic cough may be the result of aspiration of foreign objects into the lungs (usually in children). It is very important to obtain a chest x-ray if a chronic cough is present. The following pertains to patients who have a normal chest x-ray.
Cigarette smoking is the most common cause of chronic cough.
Asthma is a disease of airways, resulting in difficulty breathing or wheezing often characterized by abnormal breathing tests. Some asthma sufferers have chronic cough as their only symptom. They may even have normal lung functions tests. This is often referred to as cough-variant asthma. Asthma symptoms can be aggravated by cold air, exposure to air pollutants or pollen, smoke, or perfumes. For further reading, please read the Asthma article.
Gastroesophageal reflux disease (GERD) refers to reflux, or backward flow, of stomach acid and other contents into the esophagus. If stomach acid moves backward up the esophagus, reflexes result in spasm of the airways that can cause shortness of breath and coughing. In some instances, reflux can be so severe that substances can be aspirated into the lungs and cause similar symptoms as well as damage to lung tissue. In some individuals, no sensation of heartburn is felt and their only symptom may be cough.
Sinus problems and postnasal drip can also cause chronic cough. This condition can be difficult to detect. Sometimes CT scan of the sinuses is necessary for diagnosis. Patients often complain of a "tickle in their throat" and frequent throat clearing. For further reading, please read the Sinus Infection article.
Infections such as bronchitis or pneumonia can cause coughing. These infections can be caused by virus, bacteria or fungus. Viral infections do not respond to antibiotics. In patients with asthma, viral upper respiratory infections often result in a protracted cough even after the infection has cleared.
Certain medications, notably ace inhibitors [enalapril (Vasotec), captopril (Capoten) etc.] used in treating high blood pressure, can cause chronic cough.
Less common causes can also include tumors, sarcoidosis or other lung disease.