Acute sinusitis is a bacterial infection, most commonly affecting the sinus cavities underlying the cheeks (maxillary sinuses) and/or the bridge of the nose (ethmoid sinuses). Sinusitis typically follows a viral upper respiratory infection with symptoms that include nasal blockage, thick, discolored nasal discharge/post-nasal drip, sinus tenderness, cough and fatigue. The infection is termed chronic sinusitis when it has persisted for at least 12 weeks. Uncontrolled allergies can predispose patients to sinus disease as allergic inflammation traps and promotes bacterial growth. Medical history and physical exam are used to diagnose sinusitis; occasionally, radiologic imaging of the sinuses by CT scan will be obtained in more challenging cases. Treatment may include antibiotics, topical and oral anti-inflammatory medications, decongestants, hydration, and saline sinus rinse.