FLG and Alzheimer disease: The mechanism of AD occurrence is multifactorial, genetic factor of filaggrin (FLG) gene mutation, epidermal barrier dysfunction with decreased diversity of the microbiome, environmental factors of allergens and irritants permeation, type 2 skin inflammation activation, immunological dysregulation, and neuroimmune induced itch-scratch cycle, all of these factors lead to the occurrence of AD (3).