In psoriasis, pruritus involves Substance P, IL-2, calcitonin gene-related peptide (CGRP), μ-opioid receptors (OPRM), and κ-opioid receptors (OPRK), while in AD pruritus is linked to thymic stromal lymphopoietin (TSLP), CGRP, IL-4, IL-13, and IL-31. This evidence concerns the gene IL4 and psoriasis.