What is the relationship between sinusitis and allergic rhinitis?

Link Between Sinusitis and Allergic Rhinitis

Allergic rhinitis commonly precedes and predisposes to the development of recurrent or chronic sinusitis, with 40-84% of adults with chronic rhinosinusitis having coexisting allergic rhinitis, making it one of the most important underlying causes of sinusitis. 1

Epidemiological Evidence of the Association

The relationship between allergic rhinitis (AR) and sinusitis is well-established through multiple lines of evidence:

• In children, AR is found in 36-60% of patients with chronic sinusitis 1
• In young adults with acute maxillary sinusitis, AR prevalence is 25-31% 1
• In adults with chronic sinusitis, AR prevalence ranges from 40-84% 1
• Patients with AR have approximately twice the rate of abnormal CT scans compared to normal subjects (67% versus 33%) 1
• Extensive sinus disease on CT imaging is associated with allergy in 78% of patients 1
• Seasonal sinusitis accounts for 43% of acute sinusitis cases, with allergic etiology being the suspected cause 1

Pathophysiological Mechanisms Linking the Two Conditions

Primary Mechanism: Obstruction and Inflammation

Allergic inflammation causes nasal congestion and mucosal swelling that obstructs or impedes normal sinus drainage through the ostia. 1 This creates a cascade of pathological events:

• Obstructed sinuses partially fill with secretions and consume trapped oxygen 1
• The environment becomes acidotic, leading to impaired mucociliary function 1
• Secretions become impacted and stagnant 1
• Bacteria multiply in this favorable environment, infecting the mucosal lining 1
• Inflammatory responses lead to granulocyte influx, further swelling, pain, and thickened secretions 1

Experimental Evidence

Nasal allergen provocation studies provide direct experimental evidence of the AR-sinusitis link: 1

• In 73 separate nasal provocation tests, 32 patients developed increased sinus mucosal edema and opacification on x-ray films 1
• These patients experienced increased maxillary sinus pressure, acute headaches, and otalgia 1
• Sinus fluid from chronic sinusitis patients contains allergic mediators (histamine, leukotrienes), inflammatory cells (eosinophils), and cytokines 1

Important Caveat

Not all evidence uniformly supports this association. Some studies examining ragweed-sensitive subjects during allergy season showed no consistent CT abnormalities, and other studies failed to confirm differences between allergic and nonallergic subjects with sinusitis on CT imaging 1. The question of whether allergen directly enters the sinus cavity remains unresolved, with radiolabeled pollen studies showing no evidence of direct sinus entry 1.

Clinical Severity and Imaging Correlations

Patients with both AR and chronic rhinosinusitis are more symptomatic than nonallergic patients with similar CT findings. 1 Additionally:

• Sinusitis in AR patients is associated with more extensive CT abnormalities 1
• Higher prevalence of mucoperiosteal disease appears on CT imaging in allergic versus nonallergic patients 1
• The hyperresponsive state associated with AR may increase susceptibility to inflammation within the nose and paranasal sinuses 1

Clinical Implications for Management

Evaluation Recommendations

Patients with recurrent or chronic sinusitis should be evaluated for the presence of underlying allergy. 1 This is a formal guideline recommendation, though testing remains optional because substantive evidence for consistent treatment benefit is limited 1.

Treatment Considerations

Effective treatment of AR may decrease sinusitis frequency by reducing inflammation and swelling that compromises sinus outflow, though few studies have focused on this specific endpoint. 1 Management options when allergy is confirmed include:

• Environmental control measures 1
• Pharmacologic therapy 1
• Immunotherapy as an immunomodulating approach 1

Important Limitation

For acute bacterial rhinosinusitis (ABRS), the clinical impact of coexisting AR is small (6-8% increased risk of prolonged course) and does not support different management approaches. 1 Limited data support that allergen avoidance or immunotherapy definitively improves chronic rhinosinusitis or recurrent acute rhinosinusitis outcomes 1.

Role of Nonallergic Rhinitis

Nonallergic rhinitis (NAR) also frequently occurs in patients with chronic sinusitis and may predispose to sinusitis development. 1 NAR affects approximately 40 million Americans either alone or combined with AR, with prevalence ranging from 17-52% in rhinitis patients 1. The primary symptoms—congestion and increased secretions—are commonly found in sinusitis patients 1.