Comparison between nasal provocation tests and skin tests in patients treated with loratadine and cetirizine

Background: The effect of H1-blockers may differ depending on the target or gan. Objective: A double-blind, placebo-controlled study was carried out to comp are the effect of a 7-day treatment with loratadine (10 mg daily) or cetiri zine (10 mg daily) on nasal challenge with grass pollen grains and skin tes ts with allergen or histamine. Methods: Twenty-four patients were enrolled, but the analysis was carried o ut on 23, Nasal challenge was carried out by using 5-fold increasing number s of pollen grains. Skin prick tests were done with serial concentrations o f allergens and 1 concentration of histamine. Patients were tested in a cro ss-over design, with each treatment being administered for the previous 7 d ays and with a 2-week washout period. Results: By comparison with placebo, loratadine and cetirizine increased si gnificantly the threshold number of pollen grains required to induce a posi tive nasal challenge (P < .001). There was no difference between loratadine and cetirizine, Skin test responses to allergen were significantly reduced by loratadine and cetirizine by comparison with placebo. Skin test respons es to histamine were significantly decreased by the 2 H1-blockers, but they were more profoundly decreased by cetirizine than by loratadine. Conclusions: Both Hi-blockers reduced similarly allergen-induced skin test and nasal challenge responses. Cetirizine was more effective on histamine s kin test responses.