What is Chronic Sinusitis? Chronic sinusitis is a common condition in which the sinuses become inflamed and swollen for at least 12 weeks, despite treatment attempts.  This condition interferes with drainage and causes mucus buildup.  Breathing through your nose might be difficult and the area around your face might feel swollen, causing pain.  Chronic sinusitis can be brought on by an infection, by growths in the sinuses (nasal polyps) or…