AD is a complex inflammatory dermatosis, and various relevant factors have been described for its pathophysiology: immune dysregulation (Th2-driven proinflammation, elevated IL-4, IL-5, IL-13, Ig E, eosinophilia), skin barrier disruption (reduced ceramides), skin dysbiosis (Staphylococcus aureus), intestinal dysbiosis (heterogeneous), genetic factors, and external factors. This evidence concerns the gene IL5 and Alzheimer disease.