1)Acute Respiratory Infection:-Upper Respiratory Infection, Pneumonia,Bronchitis
2)Chronic Respiratory Infection:-TB, Postnasal drip
3)Airway Diseases:-Asthma, COPD
4)Irritants:-Cigarette smoking, Inhaled foreign bodies
5)Drug Induced:-Inhaled Drugs(Aerosols),ACE Inhibitors(anti-hypertensive)

PRODUCTIVE COUGH:
.It clears the excess secretions and inhaled foreign matters.
.Expectorants are used.

NON PRODUCTIVE COUGH:
.Dry cough has no useful function.
.Anti-tussives are used.

ANTI-TUSSIVE:
->They should be used for dry cough.
->Because it suppress cough reflex,it should not be used in the presence of bronchial secretions

LOCAL ANTI_ TUSSIVE:
->It reduces the sensitivity of perephral cough receptors to its activators which include irritants and autacoids(Bradykinine).

MUCOACTIVE AGENTS:
->They clear airway from mucus secretion by
   .ability to expectorate sputum.
   .mucus hyper secretion.