Effect of Loratadine/Montelukast Combination on Congestion in SAR Patients Exposed to Pollen in an EEU (Study P04822)

Inclusion Criteria: * Ages 18 years or greater, of either sex, any race. * A history of SAR due to ragweed for at least two consecutive ragweed seasons, as diagnosed by the investigator, another physician, or subject-provided history. * Positive skin prick test to ragweed allergen to be used in the EEU, unless previously done within 12 months * Minimum scores (diary evaluation time) must be achieved during pollen exposure during both a Priming Visit and the Treatment Visit: * A negative urine pregnancy test at Screening and prior to randomization at the Treatment Visit for all female subjects of childbearing potential. * Use of a medically accepted method of birth control. * In the judgment of the investigator, good health and freedom from any clinically significant disease (other than SAR) that would interfere with the study schedule or procedures, or compromise the subject's safety. * The appropriate washout times from the prohibited medications. Exclusion Criteria: * Pregnancy, intention of becoming pregnant, or lactation. * A situation or any condition that, in the opinion of the investigator, may interfere with optimal participation in the study. * Use of any investigational drugs, including placebo, within 30 days of Screening and for the duration of the study. * Current participation in any other clinical study. * Staff personnel directly involved with this study. * Dependence (in the opinion of the investigator) upon nasal, oral, or ocular decongestants, nasal topical antihistamines, or nasal steroids. * Nasal structural abnormalities, including large nasal polyps or marked septal deviation, that cause greater than 50% obstruction of nasal airflow. * Previous enrollment (ie, signed informed consent) into this study. * History of rhinitis medicamentosa. * A history of anaphylaxis or severe or serious reaction to skin testing. * A known potential for hypersensitivity, allergy, or idiosyncratic reaction to the study drugs or excipients. * Narrow-angle glaucoma, increased intraocular pressure, urinary retention, hypertension, severe coronary artery disease, ischemic heart disease, diabetes mellitus, hyperthyroidism, renal impairment, or prostatic hypertrophy; current treatment with monoamine oxidase (MAO) inhibitors. * An upper or lower respiratory tract infection within 28 days (4 weeks) before Priming (Visit 2) and thereafter.). * History of a positive test for HIV, TB (not due to vaccination), and hepatitis B (not due to vaccination) or C. * Asthma that requires medication other than occasional (\<= 3 uses per week) use of an inhaled short-acting beta-2 agonist.