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.
- Other medical conditions: The complications of cystic fibrosis, gastroesophageal reflux, or HIV and other immune system-related diseases can result in 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 viral, bacterial or fungal.
- Allergies such as hay fever: Inflammation that occurs with allergies can block your sinuses.