FLG and Alzheimer disease: A critical interspecies discrepancy requires attention: while human AD patients demonstrate FLG gene downregulation in lesional skin, FLG expression is paradoxically upregulated in NC/Nga and OVA models (Ewald et al., 2017), which may explain the discordance between the clinical study (Cho et al., 2008) showing significant FLG upregulation following Zicao treatment and the non-significant results observed in this meta-analysis.