The purpose of this study is to evaluate the relative efficacy of four dosing regimens of bilastine tablets versus placebo in subjects with SAR exposed in controlled ragweed pollen using the EEC model based on the mean change from baseline in Total Nasal Symptom Scores (TNSS). Study includes male and female subjects, aged 18 and 65 years with clinical history of SAR with seasonal onset and offset of nasal allergy symptoms during each of the last two ragweed allergy seasons and a positive skin prick test to ragweed allergen within 12 months prior to randomization.