Inflammation of the sinus. Signs include sensitivity of teeth to percussion, fever, and facial swelling. Symptoms include nasal congestion, postnasal discharge, facial pain/headache, rhinorrhea, halitosis, popping of ears, and muffled hearing. Inflammation of the maxillary sinus arises from bacterial, viral, fungal, allergic, or autoimmune origin. While acute sinusitis is usually caused by infection with a single type of bacterium or virus, chronic sinusitis is usually caused either by allergies or by infection with several types of bacteria. Infections may be of either dental or otolaryngeal origin.