Evaluation of Nonspecific Nasal Reactivity to Histamine during and after Natural Ragweed Pollen Exposure

Abstract

An increased nonspecific nasal reactivity (NSNR) to histamine or to methacholine has been reported in patients with rhinitis, but its contribution to clinical symptoms remains unclear. In the present study, the NSNR to histamine, defined as the concentration of histamine necessary to induce, after a topical challenge, a 75% decrease in nasal airflow (PC75), was significantly more severe in a group of ragweed-allergic subjects during natural exposure to pollen (PC75 = 4.65 mg/ml) than in normal volunteers (PC75 = 12.9 mg/ml, p < 0.0001). However, the basal nasal airflow rates of the two groups were not significantly different (290 and 339 cc). The NSNR correlated with skin sensitivity to ragweed (r = 0.46, p < 0.0021) or with the IgE antibody (Ab) levels (r = 0.42, p < 0.01) but not with the symptom scores. Finally, after the pollen season, the allergic group's nasal sensitivity to histamine improved significantly (PC75 = 4.65 to 9.35 mg/ml, p = 0.03) but remained different from that of the control group (13.19 mg/ml, p = 0.04).