A cough, is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles andmicrobes. The cough reflex consists of three phases: an inhalation, a forced exhalation against a closed glottis, and a violent release of air from the lungs following opening of the glottis, usually accompanied by a distinctive sound. Coughing can happen voluntarily as well as involuntarily.

Frequent coughing usually indicates the presence of a disease. Many viruses and bacteria benefit evolutionarily by causing the host to cough, which helps to spread the disease to new hosts. Most of the time, coughing is caused by a respiratory tract infection but can be triggered by choking, smokingair pollutionasthmagastroesophageal reflux diseasepost-nasal dripchronic bronchitis, lung tumors,heart failure and medications such as ACE inhibitors.

Treatment should target the cause; for example, smoking cessation or discontinuing ACE inhibitors. Some people may be worried about serious illnesses, and reassurance may suffice. Cough suppressants such as codeine or dextromethorphan are frequently prescribed, but have been demonstrated to have little effect. Other treatment options may target airway inflammation or may promote mucus expectoration. As it is a natural protective reflex, suppressing the cough reflex might have damaging effects, especially if the cough is productive.