The act of coughing is the body's way of removing foreign particles from the lungs and airways, such as dust and mucus. It is also the body's way of reacting to irritation of the airway.
Coughing is defined as a symptom, not a disease. Its characteristics and related symptoms are key to determining the cause of a cough.
Productive coughs produce phlegm that comes from the lungs or may drain from the sinuses. Common causes are viral illness, sinusitis, bronchitis, pneumonia, tuberculosis, chronic lung disease (COPD), gastroesophageal reflux disease, nasal discharge (postnasal drip), and smoking. It is recommended that a productive cough is not suppressed, to allow the mucus, dust, or foreign particle to be cleared from the lungs.
A nonproductive cough is dry and has no phlegm or sputom production. Exposure to dust or smoke can develop a dry hacking cough. The end of a cold can also develop a dry cough. Other common causes may include viral illnesses, bronchospasm (irritants or irritation of the airway), asthma, allergies, or certain medications (such as ACE inhibitors).