This differs from the single patient who experienced anaphylaxis during the MOv18 IgE clinical trial, who also experienced CTCAE grade 3 urticaria but additionally had a positive BAT result (> 3‐fold change increase in CD63 expression on basophils) when their blood was incubated with MOv18 IgE ex vivo (Table S6). The gene discussed is IGHE; the disease is anaphylaxis.