IgG4 is a particular sub-class of total IgG. In contrast to all other IgG sub-classes, IgG4 has no inflammatory properties and is linked to type I allergy. IgG4 is the “antidote” of IgE, avoiding IgE to bind to the allergen. Thus, IgG4 avoids allergic reactions. IgG4 is not involved in delayed food allergy. IgG4 can neither activate the complement system nor attract phagocytes.