Inflammation of the mucous membrane of any sinus, especially of the maxillary and nasal sinuses. It is characterized by symptoms such as headache, pain around the eyes, toothache, jaw pain, nasal discharge, postnasal drip, coughing, swelling around the eyes, a stuffy nose, fatigue, bad breath, or a sore throat. It may be of bacterial, viral, fungal, allergic, or autoimmune origin. It can present as acute sinusitis, lasting up to about four weeks, or chronic sinusitis, lasting up to three months or more. Asthma may be associated with recurrent sinusitis. Decongestants such as pseudoephedrine may be prescribed to reduce nasal swelling.