Molecular mechanisms and treatment modalities in equine Culicoides hypersensitivity

•Hypersensitivity mechanisms change with chronicity and prolonged allergen exposure.•Interaction between various signaling pathways increases complexity for therapeutic treatments.•Chronicity may be dominated by eosinophilia mediated by IL-5 secreting Th2 cells.•Recently discovered major allergens may improve allergen-specific immunotherapy.•New promising therapeutic vaccines target eosinophilia and pruritus. Equine Culicoides hypersensitivity (CH) is the most common allergic condition in horses affecting the skin. This review focuses on immunopathology and molecular mechanisms of equine CH. The role of eosinophils is emphasized, as well as disease severity and the influence of long-term chronic allergen exposure on T helper (Th) 2 cells. Using current knowledge from human allergic disorders, similar effects are hypothesized in equine patients. Key aspects of CH diagnosis and treatment are discussed, focusing on allergen specific immunotherapy and allergen-independent approaches, such as targeting hypereosinophilia through interleukin-5 and allergic non-histaminic pruritus though interleukin-31.