Equine Allergies and Immune Hypersensitivity Reactions – NAVLE Study Guide

Overview and Clinical Importance

Allergic skin diseases are among the most common dermatological conditions affecting horses worldwide. These immune-mediated disorders result from exaggerated or inappropriate immune responses to typically harmless environmental antigens, leading to significant morbidity and welfare concerns. Understanding the pathophysiology, clinical presentation, and management of equine allergies is essential for NAVLE success and clinical practice.

The Gell and Coombs classification system categorizes hypersensitivity reactions into four types, each involving distinct immunological mechanisms. In equine dermatology, Type I (immediate) and Type IV (delayed) hypersensitivity reactions are most commonly implicated in allergic skin diseases. Insect bite hypersensitivity (IBH), also known as "sweet itch," represents the most common allergic skin disease in horses globally.

Classification of Hypersensitivity Reactions

The Gell and Coombs classification divides hypersensitivity reactions into four types based on immunological mechanisms. Understanding these mechanisms is fundamental to diagnosing and treating equine allergic diseases.