To evaluate the efficacy of QAW039 225 mg b.i.d and Montelukast 10 mg q.d administered together as a free combination compared to QAW039 225 mg b.i.d monotherapy in patients with grass pollen-induced intermittent allergic rhinitis in an EEC challenge model. This will be assessed by the Total Nasal Symptom Score (TNSS) averaged over the last two hours (2-4h) of exposure following 14 days treatment with QAW039 and/or Montelukast or matched placebo.