CCL17 and Alzheimer disease: AD showed T-helper (Th) 2 skewing in both lesional skin and non-lesional skin, with a significant increase in Th2-related factors (IL-4R, IL-13, C-C motif chemokine ligand [CCL]17/serum thymus and activation-regulated chemokine [TARC], CCL24/eotaxin-2), while, the pruritus mediator IL-31 expressed only increase in lesional skin of patients with AD.