Allergic rhinitis (hay fever) can be treated successfully with allergen-specific immunotherapy (AIT) for 3-5 years. This relative expensive and prolonged treatment is not suitable for everyone and therefore it is important to predict who will benefit from this therapy early after the start of treatment.

This project will investigate whether a BAT with nasal fluid can detect inhibition during immunotherapy in comparison with a BAT with blood.

Allergic rhinitis (hay fever) can be treated successfully with allergen-specific immunotherapy (AIT) for 3-5 years. This relative expensive and prolonged treatment is not suitable for everyone and therefore it is important to predict who will benefit from this therapy early after the start of treatment. Biomarkers, like Basophil Activation Test (BAT) and IgE-facilitated allergen binding (FAB), using nasal fluid instead of blood, probably better reflect therapy effect (inhibition of an IgE-mediated allergic reaction) as the nose is the main target organ for AIT in allergic rhinitis.

This project will investigate whether a BAT with nasal fluid can detect inhibition during immunotherapy in comparison with a BAT with blood. Nasal fluid and blood samples are collected at baseline and after 8 and 16 weeks of treatment. A nasal fluid inhibition BAT is developed and validated by comparison with a BAT using serum and an IgE-FAB assay.

15 adults with birch pollen allergy, who are treated with AIT (Itulazax birch pollen tablet) and 10 adults with birch pollen allergy, who are treated with immunosuppressive medication (control group) will be included in the study.

Inclusion Criteria:

• IgE-sensitized birch pollen allergy
• Start of Itulazax therapy or immunosuppressive therapy (nasal corticosteroid and/or antihistamine eye drops)
• Signed informed consent

Exclusion Criteria:

• Other underlying chronic conditions (immunological (autoimmune or immunodeficiency), oncological)
• Unstable uncontrolled asthma
• Smoking

Birch pollen allergic patients who are treated with Itulazax (birch pollen SLIT-tablet) and birch pollen allergic patients who are treated with immunosuppressive medication (control group).