Sinusitis is inflammation that causes pain, pressure, and swelling in the sinuses. Chronic sinusitis is sinusitis that lasts for a long time, usually longer than 12 weeks.Unlike acute sinusitis, which is often due to a sinus infection, chronic sinusitis is not usually caused by bacteria and does not always get better with standard treatment, such as antibiotics.Chronic sinusitis occurs when the spaces inside your nose and head (sinuses) are swollen and inflamed for three months or longer, despite treatment.This common condition interferes with the way mucus normally drains and makes your nose stuffy. Breathing through your nose may be difficult, and the area around your eyes might feel swollen or tender.Chronic sinusitis can be brought on by an infection, by growths in the sinuses (nasal polyps) or swelling of the lining of your sinuses. Also called chronic rhinosinusitis, the condition can affect both adults and children.