A cough is a protective, natural reflex intended to keep the airway clear.
The urge to cough is a built-in reflex in your central nervous system, similar to the reflex to sneeze, swallow or yawn. The control centers for the cough reflex are in the same part of your brain where many functions related to survival are found1, showing just how important it is for your health and safety to have the ability to cough.
A cough can be triggered by both non-infectious causes, such as smoke, dust, and pet dander, or by infectious agents, like bacteria and viruses. A cough can also expel food that went down the wrong way, or a foreign object from getting into your lungs. It can be voluntary or involuntary as a reflex.
When the nerve endings in your airways become irritated by something you breathe in from the environment—like pollen or dust— the cough reflex kicks in. In this instance coughing helps you to expel the irritant.
A cough may also develop as a result of a viral infection. This type of cough can be either voluntary or involuntary, to help your lungs get rid of mucus that can accumulate from the immune response fighting the infection.