A Clinical Trial to Test How Well Two Drugs, QAW039 and Montelukast Work Both Individually and Together, to Target Allergic Rhinitis Using an Environmental Exposure Chamber

Inclusion Criteria: * Male or female aged 18-65 years inclusive, with a clinical history of intermittent allergic rhinitis with seasonal onset and offset of nasal allergy symptoms during each of the last two grass pollen allergy seasons. * A positive skin prick test at Visit 1 to dactylis glomerata with a wheal diameter equal to or greater than 3 mm and a negative control with a wheal diameter of zero. A positive skin prick test within 12 months prior to Visit 1 is also acceptable. * FEV1 measured by spirometry must be ≥80% of their predicted value at screening. If the patient does not achieve ≥80% of their predicted value this may be repeated prior to the EEC challenge at visit 2. * TNSS score ≥6 on at least one assessment during the 2h EEC challenge at Screening. Exclusion Criteria: * Use of other investigational drugs at the time of enrollment, or within 30 days or 5 half-lives of enrollment, whichever is longer; or longer if required by local regulations, and for any other limitation of participation in an investigational trial based on local regulations. * Pregnant or nursing (lactating) women, * Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using effective methods of contraception during dosing of study treatment.