What is a cough? A cough is your body’s defensive reflex that functions to keep your airways clear of irritating or obstructing substances so that you can breathe effectively. A cough can be dry or it can be productive, meaning that you are coughing up mucus (also known as phlegm or sputum). A cough is one of the most common reasons why people visit their primary care doctor. A cough is a symptom of a wide variety of mild to serious diseases, disorders and conditions. A cough can result from infection, inflammation, trauma, malignancy, airway obstruction, and other abnormal processes. You may cough after inhaling an irritant, such as dust, smoke, or pollen. A cough may also be the result of a disorder or disease, such as influenza, upper respiratory infection, or allergies. A cough can accompany serious and potentially life-threatening conditions as well, including pneumonia, acute bronchitis, bronchiolitis, asthma, malignancy, and congestive heart failure. Depending on the cause, a cough can begin suddenly and disappear quickly, such as after inhaling secondhand smoke. An acute cough that comes on suddenly and lasts up to two to three weeks can be caused by the common cold or other respiratory infection; whereas, a chronic cough over a long period of time (lasting more than eight weeks) may be caused by gastroesophageal reflux disease, asthma, or smoking. A cough can be a sign of a very serious or life-threatening disorder. If you have difficulty breathing, chest pain, rapid heartbeat, swollen legs or ankles, or are coughing up pink, frothy mucus, seek immediate medical care (911). The latter is a sign of pulmonary edema and can lead to respiratory arrest. Any sign of blood is a potentially serious problem. Seek prompt medical care if your cough is persistent, recurrent, or causes you concern.