Coughing is a protective response of our body to the invasion of foreign substances or germs in our respiratory tract. These particles irritate the inner lining of the respiratory passage and this irritation initiates a chain of events, which force the air out of the lungs by way of coughing. So a coughing is a sort of signal to you that something is wrong with your respiratory system. Types and causes of cough To find out the cause of your cough, it is necessary to answer a few questions: Have you had the cough for 2 weeks or more? Is it a dry cough or is phlegm produced? Do you have any other symptoms like fever, chest pain or breathlessness? Depending on the answers to these questions, the cause of cough can be determined. It could be due to an infection caused by a virus, bacteria or on rare occasions by a fungus. Infectious causes of cough Viral infection is the most common cause and is always associated with fever, watering of the eyes, sore throat and a running nose. Bacterial infections are usually restricted to the upper respiratory tract and cause tonsillitis; they are associated with high fever and throat pain. When the lower respiratory system is affected by bacterial infections it is called pneumonia. Pneumonia is also associated with high fever and chest pain, which worsens when you cough or breathe deeply. There may be yellowish or greenish phlegm.