Comparison of olfactory function in patients with seasonal and perennial allergic rhinitis

Hyposmia is a common symptom in allergic rhinitis. However, little is known about differences in the olfactory function of patients with seasonal or perennial allergy. A prospective controlled study was performed on 28 patients with allergic rhinitis to grass pollen and on 47 patients with allergic rhinitis to mites. Sixty-six healthy volunteers served as a control. Olfactory function was evaluated by a modified Connecticut Chemosensory Clinical Research Center testing procedure for threshold, identification, and discrimination. The grass pollen-allergic patients were tested preseasonally and after 3 weeks of intraseasonal grass pollen exposure; the mite-allergic patients and the volunteers were tested once. In the mite allergics, olfactory threshold, identification, and discrimination tests were significantly worse than in the volunteers (all P < 0.0001). In the grass pollen allergics, the results in olfactory identification and discrimination tests were not different from the controls if tested out of the season (both P > 0.05). However, in threshold testing (P = 0.0139), the results were worse. Intraseasonally, the grass pollen allergics showed a significant decrease in threshold, identification (both P < 0.0001), and discrimination testing (P = 0.0029). If the intraseasonal pollen allergics were compared to the mite allergics, they showed better results in identification (P = 0.0087) and threshold (P < 0.0001) tests, but worse results in discrimination testing (P = 0.0002). Therefore, the different kind of allergen exposure seems to result in a different pattern of allergic olfactory dysfunction.