Olfactory dysfunction in allergic rhinitis

Background: Olfactory dysfunction in patients with allergic rhinitis has long been thought to be secondary to coexisting chronic rhinosinusitis and polyposis with obstruction of airflow over the olfactory epithelium. Recent evidence suggests that the allergic inflammatory infiltrate may itself affect olfaction in the absence of mucosal hypertrophy. Objective: We undertook a study to determine olfactory function in patients with allergic rhinitis in the presence and absence of chronic sinusitis. Methods: Fifty-one subjects with symptoms of rhinitis who presented for allergy testing were administered the University of Pennsylvania Smell Identification Test. In addition each patient underwent computed tomography (CT) scanning of the sinuses. Results: Eighty percent of subjects were allergic. Subjects with allergic rhinitis and no evidence of sinusitis scored on average in the 30th percentile (95% CI 20-40th percentile) on objective olfactory testing compared to age- and gender-specific norms. Half the allergic patients were classified as normosmic, while half had some degree of hyposmia. Conclusions: Our study demonstrates that even in the absence of mucosal disease on CT scan, a significant subset of patients with allergic rhinitis will exhibit hyposmia, mostly to a mild or moderate degree. The pathophysiology and potential treatments for olfactory loss in these patients should be further explored.