There are many contributors to the pathogenesis of AD, including genetic defects in the epidermal barrier that can be explained, at least in part, by inherited mutations in keratinocyte proteins such as filaggrin and loricrin (Kim et al., 2008; Howell et al., 2009; Callewaert et al., 2020), an imbalance towards a T-helper-2 (Th2) immune response in which the cytokines IL-4, IL-5 and IL-13 play a major role (Homey et al., 2006; Brandt and Sivaprasad, 2011), and microbial dysbiosis that increases the susceptibility to AD (Bjerre et al., 2017). Here, IL4 is linked to Alzheimer disease.