For instance, filaggrin (FLG, a major structural protein in the upper epidermis) assists in the formation of the epidermal barrier (O’Regan et al., 2008; Weidinger and Novak, 2016), which presents a loss-of-function in approximately 10%–40% of patients with AD (Rodríguez et al., 2009; Winge et al., 2011; Margolis et al., 2014; Feketea and Tsabouri, 2017). Here, FLG is linked to Alzheimer disease.