Main Inclusion Criteria:  Body mass index between 18.0 and 32.0 kg/m2 inclusive. History of perennial allergic rhinitis to house dust mite for more than 1 year. Positive Skin Prick Test (SPT) for Dermatophagoides pteronyssinus (der p) allergen at screening or within 12 months prior to the screening visit.  Main Exclusion Criteria:  Any clinically relevant abnormal findings in physical examination, clinical chemistry, hematology, urinalysis, vital signs, lung function at screening visit, which, in the opinion of the investigator, may either put the subject at risk because of participation in the study or may influence the results of the study, or the subject's ability to participate in the study. Use of any medication considered to have an influence on the outcome of the study during the EEC session, at the discretion of the Investigator and/or designee. Recent nasal ulcers, mucosal erosion, nasal surgery, or nasal trauma, that might interfere with study results as determined by the Investigator and/or designee.