Chronic sinusitis is one of the more prevalent chronic illnesses, affecting persons of all age groups. It is an inflammatory process that involves the paranasal sinuses and persists for 12 weeks or longer. The literature has supported that chronic sinusitis is almost always accompanied by concurrent nasal airway inflammation and is often preceded by rhinitis symptoms; thus, the term chronic hinosinusitis has evolved to more accurately describe this condition.

CRS may manifest as one of three major clinical syndromes: CRS without nasal polyps, CRS with nasal polyps, or allergic fungal rhinosinusitis. These classifications are significant, particularly regarding therapy. Most cases of chronic sinusitis are continuations of unresolved acute sinusitis; however, chronic sinusitis usually manifests differently from acute sinusitis. Symptoms of chronic sinusitis include nasal stuffiness, postnasal drip, facial fullness, and malaise. It is believed that some underlying conditions that could possibly cause chronic sinusitis:

--Deviated septum
--Enlarged adenoids
--Aspergillosis
--Primary Immune Deficiency
--Nasal polyps
--Nasal abnormality
--Cystic fibrosis
--Immotile cilia syndrome
--Kartagener syndrome
--Wegener's granulomatosis
--Neoplasm