In fact, the three‐dimensional structure of Der p 5 has been revealed and shows a three‐helical bundle that can polymerize to create a hydrophobic cavity which could possibly be a ligand‐binding site.19 Also Der p 21 seems to have a similar three‐dimensional structure (ie, forms a three‐helical bundle protein) but shows no IgE cross‐reactivity with Der p 5.10 Here, we performed a detailed analysis of the IgE epitopes of Der p 5 and Der p 21 to break the ground for a broadly protective HDM allergy vaccine. Here, IGHE is linked to allergic disease.