IGHE and Allergy: This study, despite not comparing the reactivity of IgE antibodies to rBlo t 5 and rBlo t 21 with the reactivity to their native counterparts, suggests that recombinant allergens produced as described in this paper can replace natural allergen extracts in the diagnosis of allergies, confirming previously published data showing that rBlo t 5 expressed in E. coli and native rBlo t 5 have comparable IgE reactivity in terms of percentage of sera with antibodies [22].