FLG and Alzheimer disease: In patients with AD, the epidermis is characterized by a block in terminal keratinocyte differentiation (Guttman-Yassky et al., 2009) which leads to allergen penetration through the epidermis and systemic IgE sensitization (Jensen et al., 2004), and reduced expression of skin barrier proteins including FLG, involucrin, loricrin, as well as AMPs (Ong et al., 2002; Howell et al., 2007).