Studies have shown that SCFAs play an important role in regulating skin homeostasis: topical application of propionate reduces MC903-induced skin inflammation in a mouse model of AD by inhibiting IL-33 production in keratinocytes (Qiu et al., 2022); sodium butyrate ameliorates AD-induced inflammation through inhibition of the STAT1 and NF-κB pathways and may inhibit AD patients' growth of S. aureus on the skin (Traisaeng et al., 2019; Hu et al., 2023). This evidence concerns the gene STAT1 and Alzheimer disease.