This means that allergen-specific IgE harbored by patients with IgE-allergic AD acts not only as an effector for type I and late-phase reactions (reactions that induce itching–scratching cycles by activating MCs and eosinophils, thus exacerbating AD) [47,69], but also as an inducer and amplifier of delayed-type hypersensitivity [56,71]. This evidence concerns the gene IGHE and Alzheimer disease.