NASAL OBSTRUCTION can be temporary or permanent ;intermittent or persistent;unilateral or bilateral PHYSIOLOGICAL CYCLIC:one nostril functions more than the other in cyclic phase in normal persons POSTURAL :While lying down on one side ,the nostril on the lower side gradually gets blocked ,while the upper nostril gradually opens due to naso –pulmonary reflexes REFLEX:If thenose is exposed to cold air ,the nose gets partially obstructed reflexly to provide better air Conditioning of the inhaled air and to warm it .Exposing the head and feel to chill or cold water also causes reflex nasal obstruction PATHOLOGICAL CONGENITAL:Chonal atresia and atresia of anterior nares may occur .congenital deviation of the nasal septum is uncommon OBSTRUCTION :Deviated nasal septum is a common cause on the side opposite to the deviation ,compensatory hypertrophy of the turbinates may produce obstruction Adenoids in children are a common cause of mouth breathing TRAUMATIC :Birth trauma may deviate the septum ,but it is easily corrected by manipulating the nose External injuries may cause fracture ,dislocation of the nasal septum or septal haematoma Foreign bodies obstructed the nose by their physical presence and secondary infection INFECTION :All types of rhinitis and sinusitis causes obstruction .chronic hypertrophic rhinitis With hypertrophic turbinates is a common cause of obstruction.common cold often produces temporary Obstruction Septal abscess blocks the nose on both sides NON INFLAMMATORY RHINITIS :Allergic rhinitis ,vasomotor rhinitis MISCELLANEOUS :Nasal polyps,rhinitis medicamentosa NEOPLASMS in the nose,paranasal sinuses and nasopharynx produce unilateral nasal obstruction ,but later these may obstruct the other side also. Malignant neoplasms may be associated with blood stained discharge GENERAL CAUSES:Hypotensive drugs may produce nasal obstruction,hypothyroidism,using snuff ,smoking and alcoholism COMMON CAUSES OF NASAL OBSTRUCTION IN CHILDREN:Adenoids,rhinitis and foreign bodies. IN ADULT:Deviated nasal septum,hypertrophic turbinates,nasal allergy or vasomotor rhinitis,polyps,sinusitis and rhinitis medicamentosa IN ELDERLY:Hypotensive drugs,rhinitis medicamentosa ,malignancy in the nose,paranasal sinuses And nasopharynx should be ruled out if there is unilateral obstruction with blood stained discharge and sinusitis CAUSES OF UNILATERAL NASAL OBSTRUCTION Congenital :choanal atresia Infections:sinusitis and rhinosporidiosis Neoplasms Miscellaneous :deviated nasal septum,hypertrophic inferior turbinate ,antrochonal polyp,foreign body , rhinolith and synechia.