2.3. Blood analysis
From each individual, two blood serum tubes of 10 mL were collected. One serum tube was sent to a clinical laboratory (Labo Rigo, Genk, Belgium), where the ImmunoCAP assay from Thermo Fisher Scientific (Waltham, MA, USA) was performed to measure the total IgE-level and specific IgE-levels for respiratory allergens, according to the manufacturer’s protocol. The allergens analysed in this assay are shown in Table 1. The blood serum of the second tube was isolated, aliquoted and stored at -80°C for later use in the MSD multiplex immunoassay.