PK/PD and Steady State Efficacy Study of Bilastine Compared With Placebo Given Orally in the Treatment of the Symptoms of SAR in an EEC Model (5-arm)

Inclusion Criteria: * Clinical history of SAR for the last two ragweed allergy seasons. * A positive skin test within 12 months of screening to ragweed allergen. * A minimum qualifying symptom score on both Visits, 2 and 3. * Females must have a confirmed absence of pregnancy according to a negative urine pregnancy test. Exclusion Criteria: * Women who are pregnant, breastfeeding, or planning a pregnancy. * History of more than mild asthma. * History of clinically significant (as determined by the Investigator) active perennial allergic rhinitis to which the subject is regularly exposed. * Non-allergic rhinitis (vasomotor or rhinitis medicamentosa). * An anatomic abnormality that interferes with assessment of nasal function. - History of clinically significant recurrent sinusitis or chronic sinusitis. - Clinically significant (as determined by the Investigator) cardiovascular, hepatic, neurologic, psychiatric, endocrine, or other significant systemic disease that makes implementation of the protocol jeopardizing to the safety of the subject. * A need for use of antihistamines or corticosteroids on a regular basis (systemic or topical). * Currently taking monoamine oxidase (MAO) inhibitors. * Taken any systemic corticosteroids, immunomodulators, or immune suppressive medications within four weeks prior to Visit 1. * Taken any antihistamine within seven days prior to Visit 1 skin testing. * Known current alcohol or drug abuse. * Current participation in another clinical study involving an experimental treatment, or participation in such a study within 30 days prior to study entry. - History of generalized anaphylaxis requiring medical attention. * Clinically significant abnormality of screening blood chemistry, hematology, or urinalysis.