Allergy is an immune system disorder characterized by an exaggerated response to normally harmless substances, known as allergens. These may include pollen, dust mites, animal dander, foods, or medications. Allergic reactions are mediated by immunoglobulin E (IgE) antibodies, leading to the release of histamine and other inflammatory mediators. Clinical manifestations range from mild symptoms, such as rhinitis and dermatitis, to severe and potentially life-threatening conditions like anaphylaxis. Allergy research and diagnostics are crucial for understanding immune hypersensitivity and developing effective prevention and treatment strategies.