IGHE and allergic disease: Previously, it was demonstrated that Bet v 1 is the primary sensitizer in allergies to the birch-related trees of the order Fagales and that the cross-reactivity of Bet v 1-specific IgE antibodies with its homologous pollen allergens (alder Aln g 1, hazel Cor a 1, etc.)triggers respiratory allergic symptoms beyond the birch pollen season [4].