The precise etiology of chronic rhinosinusitis (CRS) is unknown.

In considering the possible causes of chronic rhinosinusitis, it is important to consider that CRS may not be a single disorder with a single cause. Instead, CRS may be a poorly characterized syndrome with multiple discrete causes. Unfortunately, science has not explained the exact cause of chronic rhinosinusitis.

Numerous causes for chronic rhinosinusitis have been proposed:


Some studies have shown that inhalant allergy seems to occur more commonly in patients with CRS than in the general population; thus, it has been proposed that allergy may be a factor in the development of CRS.

Bacterial Infection

In at least some patients with CRS, the presence of specific bacteria seems related to the status of the CRS. In this view, bacteria start and sustain the process of chronic rhinosinusitis.


Biofilms are complex, three-dimensional structures of living bacteria. They have been identified in approximately 25-33% of patients with chronic rhinosinusitis in some studies.

Fungal Infection

Cultures of sinus secretions from patients with chronic rhinosinusitis have grown fungus. Furthermore, it has been shown that the immune system of patients with CRS have a greater response when exposed to fungal proteins at least in the laboratory.

Genetic Disorders

Patients with cystic fibrosis (CF), a hereditary condition that effects mostly the lungs, also develop significant CRS. CF and other genetic diseases may be causes of chronic rhinosinusitis.


The bone in the walls of the sinuses of patients with severe CRS undergoes a remodeling process that produces thicker, but abnormal bone. This finding, known as osteitis, suggests that changes in the bone may contribute to chronic rhinosinusitis.

Mucociliary Dysfunction

Under normal circumstances, the lining of the sinuses is covered by a think blanket of mucus, which is propelled in a programmed fashion by cilia on the surface of the sinus lining. These cilia act as oars to move the mucus. Disruption of this activity leads to stagnation of the mucus, and eventually infection and CRS.

OMC Compromise

The ostiomeatal complex region is the common outflow channel for the anterior ethmoid, frontal and maxillary sinuses. Blockage of the OMC causes blockage of the ‘upstream’ sinuses and chronic rhinosinusitis.

Staphylococcal Superantigen

Certain species of Staphylococcus can secrete substances (known as exotoxins) that can directly stimulate the immune system to produce a strong inflammatory reaction and CRS.


ASA triad (also known as Samter’s triad) is characterized by nasal polyps, asthma and aspirin intolerance. In these patients, aspirin produces a skin reaction, asthma and even a severe reaction that can be life threatening.

Churg-Strauss Syndrome (also known as granulomatous vasculitis) results from an inflammation of blood vessels. Patients with this condition have severe asthma, sinusitis and other related illnesses.