Coughing is a symptom of any normal infection of the respiratory tract, such as: colds, flu or bronchitis.
Its function is cleansing the airways from phlegm and also form tiny particles that enter the airways by mistake. As such it belongs to the airway defense mechanism.
Coughing may also be the result of airway irritation - by smoke or different air pollutants.
Ther are some breast diseases that can cause chronic cough.
But In most cases, coughing helps cleansing the body and there is no need for suppressing it, unless it becomes very bothering.
If we suffer from coughs with blood or green rusty mucus, it is very recommended to consult a doctor.