Equine Interleukin-13 (IL-13) is a Th2-associated cytokine produced primarily by activated CD4⁺ T helper 2 (Th2) cells and other type 2 immune populations in horses (Equus caballus), where it plays a central role in regulating allergic inflammation, mucosal immunity, and tissue remodeling. IL-13 signals through receptor complexes composed of IL-13Rα1 and IL-4Rα, activating JAK/STAT6 pathways that promote alternative macrophage activation, mucus production, IgE-associated immune responses, and modulation of pro-inflammatory cytokine signaling. In equine health, IL-13 is particularly relevant in allergic and inflammatory conditions such as equine asthma (recurrent airway obstruction), insect bite hypersensitivity, parasitic infections, and certain gastrointestinal inflammatory disorders, where Th2 polarization contributes to eosinophilic infiltration, airway hyperreactivity, and tissue remodeling. While IL-13 supports parasite defense and tissue repair, excessive or chronic IL-13 signaling may contribute to airway fibrosis and persistent inflammation. As a biomarker of type 2 immune activation, equine IL-13 is important in studies of allergic disease pathogenesis, vaccine responses, and immune regulation. In translational research, horses serve as valuable large-animal models for human asthma and allergic airway disease, and characterization of equine IL-13 supports comparative investigations into Th2-mediated inflammation and development of targeted anti-cytokine therapies relevant to both equine and human medicine.