EPOS 2007 states that chronic rhinosinusitis is a persistent inflammatory and infectious process of the nasal mucosa, a chronic course with multiple inflammatory factors involved. The involvement of multiple inflammatory and infectious factors in the chronic process should be the basis of the complexity of the disease. The main causes of the disease can be categorized into two aspects: local and systemic factors. Local factors refer to chronic inflammation and persistent infection confined to the sinuses themselves, of which the most common causes can be considered as improper perioperative management on the basis of chronic inflammation of the mucosa, unreasonable surgery, or excessive damage to the nasal sinus mucosa or mucoperiosteum during surgery; other factors are osteitis, bacterial biofilm, fungal and bacterial superantigenic factors. Systemic factors mostly originate from systemic inflammatory reactions or local manifestations of systemic lesions in the mucosa of the nasal sinuses, such as: allergic reactions, asthma, eosinophilic chronic sinusitis and nasal polyps, primary ciliary dysfunction, poor aspirin tolerance, immunodeficiency (especially IgG and its subtype deficiency), reflux disease, etc.