Human Interleukin-31 (IL-31) is a cytokine involved in the regulation of immune responses and inflammatory signaling in humans (Homo sapiens). IL-31 is produced primarily by activated T helper 2 (Th2) cells, as well as by other immune cells such as mast cells and macrophages following immune stimulation. Human IL-31 binds to a heterodimeric receptor complex composed of IL-31 receptor A (IL-31RA) and oncostatin M receptor (OSMR), activating intracellular signaling pathways including JAK–STAT, MAPK, and PI3K that regulate gene expression, inflammation, and cellular responses. Through these signaling pathways, IL-31 contributes to communication between immune cells and epithelial tissues and plays a key role in regulating inflammatory processes, particularly in the skin and mucosal tissues. In humans, IL-31 has been strongly associated with pruritus (itch) and inflammatory skin diseases such as atopic dermatitis and chronic pruritic disorders. Due to its involvement in allergic inflammation and itch signaling, human IL-31 is widely studied in immunology and translational biomedical research, including investigations of allergic disease mechanisms and development of targeted therapies for inflammatory skin conditions.