IGHE and anaphylaxis: [104] suggested that allergic susceptibility arises not only from gain‐of‐function mutations, but also from loss‐of‐function mutations with impaired IL‐4Rα/PI3K signaling attenuating IL‐4 driven CD4+ T‐cell proliferation, reducing T cell tolerance, enhancing IgE production, and predisposing to allergic asthma and anaphylaxis.