Study to Compare the Effect of a Combination of Cetirizine With Pseudoephedrine Versus Placebo on Symptoms in Patients With Allergic Rhinitis Within/Out of Season

A previous study has shown very clearly that the treatment with the combination of cetirizine and pseudoephedrine is superior to the treatment with the single agents regarding the reduction of symptoms in patients with allergic rhinitis. These data, obtained after controlled pollen exposure out of the pollen season, showed highly reproducible individual responses prior to dosing. It is not clear, however, whether the same results can be obtained during the pollen season, when additional natural pollen exposure may influence the variability of the individual reactions.