Particularly, interleukin-4 (IL-4) and IL-13 have been reported to cause significant downregulation of proteins involved in the formation of the cornified envelope (i.e., FLG, loricrin, and involucrin), and inhibition of IL-4 restores the expression levels of these important regulators, demonstrating the role of type 2 cytokines in regulating epidermal barrier function in AD [27,28,29]. This evidence concerns the gene FLG and Alzheimer disease.