Comparison of the response to histamine challenge of the nose and the maxillary sinus: effect of loratadine

To study the response of the maxillary sinus to histamine provocation, we p erformed a double-blind, randomized, crossover trial during which nonallerg ic subjects without symptoms of rhinitis (n = 25) received either 10 mg lor atadine or placebo once daily for a week and then underwent nasal challenge with histamine (3, 10, and 30 mg/ml) followed, 24 h later, by a maxillary sinus challenge while still receiving the medication. Nasal challenge with histamine led to significant increases in vascular permeability, reflex nas al secretions, sneezing, and other nasal symptoms. Sinus challenge resulted in significant increases in vascular permeability within the sinus cavity (P < 0.01) and some nasal symptoms but no significant change in reflex nasa l secretions. The response of the sinus mucosa to histamine was lower in ma gnitude than that of the nose. Treatment with loratadine resulted in a sign ificant inhibition of the histamine-induced changes in both nasal and sinus cavities. Our data suggest the lack of a sinonasal reflex response to hist amine provocation of the maxillary sinus of nonallergic individuals.