IGHE and Alzheimer disease: Moreover, studies using transgenic models have demonstrated that IL-4 not only amplifies the inflammatory response but also plays a crucial role in initiating the AD phenotype—leading to the development of characteristic skin lesions, such as pruritus, infiltration of immune cells, and elevated IgE levels—whereas its absence correlates with improved barrier function and increased expression of genes from the epidermal differentiation complex (EDC) [82,83].