IL4 and Alzheimer disease: Cytokines such as IL-4 and IL-13 exert a direct key influence on the epidermis of the patients with AD by (1) blocking terminal differentiation with potential hyperplasia of the regulatory loop (hyperprolifieration of keratinocytes), (2) stimulation of remodelling of the skin towards sponge layer, (3) inhibition of lipid synthesis in the skin, (4) reduced synthesis of antimicrobial peptides (22) and (5) facilitation of the skin colonization by S. aureus (23).