This is a phase II study in patients with seasonal allergic rhinitis (SAR) and will compare the effect versus placebo of two different oral doses of BLX-028914 in an allergen challenge model. BLX-028914, a selective phosphodiesterase-4 (PDE4) inhibitor with a promising safety profile,is currently under development for treatment of airway diseases by Orexo AB, Sweden.

The aim of this study is to compare the effect, safety and tolerability of 14 days treatment with BLX-0289014 in patients with SAR in an allergen challenge model versus placebo.

Inclusion Criteria:

• 18 to 50 years of age (inclusive), male or female
• Body Mass Index (BMI) between 18 and 28 kg/m2 (inclusive)
• History of pollen-induced seasonal allergic rhinitis but otherwise healthy
• Positive skin prick test for timothy and/or birch allergen
• Sufficient reaction to nasally administered allergen at screening
• Signed informed consent obtained

Exclusion Criteria:

• Expected symptoms of seasonal allergic rhinitis during the study period
• Asthma
• Nasal anatomical deviations, ongoing nasal symptoms, ongoing upper respiratory tract infection
• Anti-allergy immunotherapy in the previous two years
• Extensive use of nasal sprays
• Any medication except for contraceptives, during their last five half- lives prior to the first treatment period except for occasional OTC analgesics
• Ingestion of grapefruit or grapefruit juice or herbal remedies (e.g. St John's-wort) that may effect the enzyme CYP3A4
• Smoking within 3 months of first treatment period
• Clinically significant laboratory findings
• Pregnant or breast feeding woman or woman of childbearing potential not using adequate birth control
• Known hypersensitivity to any constituent of the study medication or placebo
• Participation in any other investigational study in the last three months
• Subject anticipated not being able to adhere to study plan according to investigator judgement