Reduction of soluble ICAM-1 levels in nasal secretion by H1-blockers in seasonal allergic rhinitis.

ICAM-1, a transmembrane glycoprotein promoting adhesion in immunologic and inflammatory reactions, was found to be increased on nasal epithelial cells of patients with allergic rhinitis. Loratadine, an H1-blocker, was found to reduce in vitro the expression of ICAM-1 on nasal epithelial cells. A double-blind, parallel-group study was carried out during the pollen season to compare the effect of two H1-blockers, cetirizine (10 mg OD) and loratadine (10 mg OD), on the release of soluble ICAM-1 in nasal secretions. A group of untreated patients was used as a control group. sICAM-1 was measured by enzyme immunoassay before and after 2 weeks of treatment. Symptoms were significantly decreased in the actively treated groups. sICAM-1 levels were unchanged in the control group but were significantly reduced in the two treated groups (P < 0.015, Wilcoxon's W test). This study shows that two H1-blockers, loratadine and cetirizine, have a similar effect on sICAM-1 released in nasal secretions during the pollen season.