The purpose of this study is to investigate if ONO-4053 relieves symptoms of allergic rhinitis in seasonal allergic rhinitis subjects exposed to pollen under controlled conditions.

The purpose of this study is to investigate if ONO-4053 will impact allergic rhinitis symptoms in subjects with seasonal allergic rhinitis when they are exposed to pollen administered at a fixed rate in an inhalation exposure chamber compared to the standard treatment Cetirizine 10mg under the same conditions.

Inclusion Criteria:

• The subject is aged between 18 and 65 years inclusive, and healthy with the exception of allergic rhinitis or mild asthma that does not require treatment and has provided written informed consent, which signifies an agreement to enter the study and comply with the restrictions and requirements listed in the informed consent form.
• The subject exhibits a moderate to severe response to grass pollen grains in the allergen challenge chamber at Screening.

Exclusion Criteria:

• The subject on examination is found to have nasal structural abnormalities or nasal polyps; a history of frequent nose bleeds, nasal biopsy, nasal trauma or nasal surgery.
• Pregnant or breast-feeding females.