Cough is an involuntary reflex. It is not an illness, but rather a protective reflex. The reflex occurs when the membranous lining of the respiratory tract secrete excessive mucous which protects the airway from infections. This mucous collects and traps all the foreign particles which enter the airway. Coughing helps us get rid our throats of this mucous. This enables us to keep our airways open and also prevent further infections like pneumonia which can occur.

Types of Cough
Cough can be classified on the basis of the duration for which they last and also the content of the sputum they produce.

Duration of Cough
A cough can come and go quickly or it can last for several days if you have a cold, or it can be persistent and chronic, as in the case of chronic bronchitis.

Sputum production
Based on this, there are two types, the dry cough or the cough where the sputum lining the respiratory passage comes out and the wet cough.

Coughing being mostly involuntary can also be voluntary. In addition, some people cough more often than others because individuals vary in the amount of irritation they can tolerate.

Symptoms of Cough
The main symptom is involuntary coughing. It could be accompanied by other symptoms like fever, difficulty in swallowing, throat ache, pain in the ribs etc. More important than the cough itself, are aspects of it that provide clues to its causes:

• Frequency and duration of the cough.
• Type of material being coughed up (mucus or phlegm, blood).
• Colour of the sputum (white, clear, green, yellow, pink, blood–specked).
• Consistency of the material coughed up (thick, thin, frothy).
• Presence or absence of accompanying pain.