Interleukin-31 （IL-31） is a cytokine that belongs to the IL-6 cytokine family and is primarily produced by activated T helper type 2 （Th2） cells. IL-31 signals through a heterodimeric receptor complex composed of IL-31 receptor A （IL-31RA） and oncostatin M receptor （OSMR）, leading to the activation of downstream signaling pathways such as STAT1 and STAT3. IL-31 is involved in various inflammatory and immune responses, and has been implicated in the pathogenesis of allergic diseases, skin disorders, and chronic inflammatory conditions. In mouse models, IL-31 has been shown to play a role in pruritus （itching） and dermatitis, highlighting its importance in mediating inflammatory responses in the skin.