IGHE and food allergy: IgG4 levels have been shown to increase in patients who naturally outgrow IgE-mediated food allergy, such as cow's milk allergy,6,7 and in patients who are submitted to food oral immunotherapy8,9 and immunotherapy to respiratory allergens.10–12 Whether IgG4 can play an inhibitory role in the allergen-IgE interaction in sensitized but otherwise tolerant patients is unknown.