The goal of this exploratory pilot study is to generate early data needed for future validation studies of the automated BÜHLMANN BAT (Basophil activation test) assay. The main questions it aims to answer are:

Does the BAT assay use the optimal allergen concentrations for stimulation, and how do its preliminary cut-offs perform in a real-world clinical scenario?

Participants older than 1.5 years who are being evaluated for possible allergy sensitization will provide one additional blood tube during their routine blood draw as part of the regular medical care. The study involves only one visit and does not provide direct personal benefit.

Inclusion Criteria:

• Individuals with diagnosis of a hypersensitivity / allergy to one of the 6 allergens, established according to common clinical practice

Exclusion Criteria:

• Pregnant women
• Children under the age of 18 months
• Individuals under therapy with Omalizumab or Rituximab
• Individuals with an allergic reaction less than two weeks before blood sample collection
• Individuals under therapy with BTK inhibitors
• Individuals receiving allergen specific immunotherapy (ASIT)
• Subjects with active infection and inflammatory conditions
• Patients who are unable to understand the study information and informed consent form in German

Participants will be invited during a routine diagnostic visit to the Klinik und Poliklinik für Dermatologie und Allergologie am Biederstein to contribute to the study by giving one additional sample tube. This extra sample will be collected alongside the venous blood samples already being taken as part of their standard care.