Sweat Hypersensitivity-Induced Urticaria and Sebaceous Adenitis in an American Saddlebred

The study described a unique case of a 5-year-old American Saddlebred gelding with chronic dermatitis and nonseasonal pruritic urticaria triggered by its own sweat, leading to severe pruritus and alopecia. Diagnostic tests ruled out parasites and infections, identifying sebaceous adenitis and cholinergic urticaria as potential causes. Intradermal tests confirmed hypersensitivity to autologous sweat, suggesting an immune-mediated mechanism. Despite attempts at desensitization, the horse was euthanized before efficacy could be determined. This case was the first known instance of sweat hypersensitivity and progressive sebaceous adenitis in a horse, highlighting the potential role of sweat leakage due to lymphocytic inflammation in developing hypersensitivity.