Causes

Common causes of chronic sinusitis include:

• Nasal polyps. These tissue growths can block the nasal passages or sinuses.
• Deviated nasal septum. A crooked septum — the wall between the nostrils — may restrict or block sinus passages, making the symptoms of sinusitis worse.
• Other medical conditions. The complications of conditions such as cystic fibrosis, HIV and other immune system-related diseases can lead to nasal blockage.
• Respiratory tract infections. Infections in your respiratory tract — most commonly colds — can inflame and thicken your sinus membranes and block mucus drainage. These infections can be caused by viruses or bacteria.
• Allergies such as hay fever. Inflammation that occurs with allergies can block your sinuses.