Sinusitis is infective inflammation of the mucosal lining of one or more of the nasal sinuses. There is invariably associated changes in the lining tissue of the nose, hence the term rhinosinusitis. Swelling of the lining sinus mucosa leads to blocked drainage and ciliary malfunction which interferes with the transport of secretions. This leads to bacterial overgrowth and the production of yellow or green (purulent) mucus and an infective nasal discharge with nasal congestion. The cheek (maxillary) and front nasal bridge (anterior ethmoid) sinuses are commonly affected first, and often causes facial pressure and discomfort. An upper respiratory tract infection (URTI) and allergic rhinitis are common triggers.