IL-31 (Th2-associated cytokine) has also been reported to be an endogenous cause of itching [6], and AD is closely related to pro-inflammatory cytokine (TNF-α, IL-6, GM-CSF, G-CSF and others) released by keratinocytes, dendritic cells, macrophages and other immune cells [3,7]. Here, CSF2 is linked to Alzheimer disease.