Monomer. Trimer of homodimers. Oligomerizes in a concentration-dependent manner. Causes an allergic reaction in human. Common symptoms of mite allergy are bronchial asthma, allergic rhinitis and conjunctivitis. Binds to IgE in patients allergic to house dust mite (HDM) (PubMed:7798547, PubMed:2794865, PubMed:18445190, PubMed:24874917, PubMed:29319884, PubMed:20534590). Recombinant protein binds to IgE in 52% of the 25 patients tested (PubMed:7798547). Recombinant protein binds to IgE in 31% of the 117 patients tested living in urban area in Austria allergic to European HDM (PubMed:18445190). Recombinant protein binds to IgE in 69% of the 96 patients tested living in Bangkok allergic to European HDM (PubMed:24874917). Recombinant protein of 34-132 binds to IgE in 35% of the 62 patients tested (PubMed:20534590). In the skin tests, the recombinant protein produces positive reactions in 67% of the 15 patients tested with asthma and allergic rhinitis, in 58% of the 13 patients tested with asthma alone and in 29% of the 17 patients tested with allergic rhinitis alone (PubMed:7798547). No relevant cross-reactivity with Der p 21 allergen (PubMed:29319884). Causes histamine release from human peripheral blood mononuclear leukocytes. Up-regulates expression of CD203c activation marker on basophils (PubMed:18445190). Non-allergenic peptides identified from the mapped major conformational IgE epitope-containing areas could be used for the engineering of house dust mite allergy vaccine. Belongs to the mite group 5 allergen family. Extended N-terminus.