IGHE and anaphylaxis: An endotype has been defined as “a compilation of disease mechanisms explaining disease expression within certain groups of patients”, and in the case of anaphylaxis, endotypes have included allergic/immune- (IgE or IgG-mediated), contact system-, cytokine-(cytokine release reactions or CRRs—which could be mixed due to co-occurrence of IgE-mediated reactions and cytokine storm reactions or CSRs), mast cell activation- (direct mast cell activation or clonal mast cell disorders), and complement-mediated reactions (Figure 1) [2,14,15,16,18].