Sinusitis is inflammation and swelling of the lining membranes of the sinuses. This is commonly caused by bacterial or viral infections or blockage of the sinus openings by thickened mucosa called polyps. Symptoms of sinusitis include facial pain or pressure, nasal obstruction, discolored nasal drainage, loss of sense of smell, and headaches. The majority of patients with sinusitis can successfully be treated with antibiotics or other medications, treatment of allergies or environmental control.