Cough is a natural reflex of the body that can facilitate better breathing by clearing the airways. The function of cough is to protect the lungs from irritating substances. It is normal to cough a little bit sometimes. However, chronic cough indicates that there may be problems in the respiratory system or other parts of the human body. Cough can either be productive which produces excessive mucus or phlegm, or non-productive which has no mucus or phlegm. Non-productive cough can be described as dry cough which is caused by inflammation of the upper airway due to dust, foreign bodies or a throat infection.