IGHE and food allergy: It is conceivable that, when allergen is introduced early as a method of prevention of food allergy, the same blocking mechanism of IgG4 contributes to reduced IgE-antigen crosslinking, reduced type 2 cytokine production by CD4+ T cells, and reduced production of IgE, thus facilitating a state of tolerance that persists even when IgG4 levels decline after prolonged consumption or cessation of antigen exposure, as seen at 72 months in the LEAP trial.