Most common cause of U/L mucopurulent rhinorrhea in a child is:
A unilateral nasal discharge is nearly always due to foreign body and if duscharge has an unpleasant smell,it is pathognic. If a child presents with unilateral,foul smeling nasal discharge,foreign body must be excluded. Ref Dhingra 6/e,p 161.
Foreign body
Adenoids which are blocking the airways
Deted nasal septum
Inadequately treated acute frontal sinusitis
Nose and paranasal sinuses