Some studies have reported increased IL-31 serum levels (sIL-31) in itching diseases, and most of them have provided evidence for a positive correlation between sIL-31 and itch severity in AD [31, 32, 34, 36] and CTCL [47, 49, 50], with some contradictory results [51, 52]. This evidence concerns the gene IL31 and Alzheimer disease.