Inhalant Mediated Allergy: Immunobiology, Clinical Manifestations and Diagnosis

Inhalant allergen-mediated respiratory diseases, including asthma and allergic rhinitis, have become increasing global health issues. While air pollution is believed to favor allergic sensitization and intensify clinical symptoms of allergy, allergen sensitization can vary highly with geographical location, climate, and lifestyle differences. Pollen sensitization is higher in European countries, while dust mite is more common in regions with high humidity. Domestic pet sensitization is on the rising trend in industrialized nations, but the paradoxical effect of intensive cat exposure in early childhood is also observed. Clinical management of inhalant allergic diseases has greatly benefited from the immunological and mechanistic understanding of pathophysiology. In this review, we discuss the current knowledge on inhalant mediated allergic disorders with emphasis on (1) the major immune cells and relevant chemokines and cytokines in the sensitization and effector phase with aeroallergen exposure, (2) their manifestation in asthma and allergic rhinitis, (3) characterization of inhalant allergens, (4) chemical contributions to the development of allergic diseases, and (5) clinical diagnosis of aeroallergen sensitization and management of inhalant allergy. Knowledge on the role of Th2 skewing, IgE, basophil, mast cells, and eosinophils in respiratory allergic diseases are fundamental in the diagnosis and management of these disorders. Skin test, basophil activation test, and specific IgE component-resolved diagnostics are used for diagnosis and facilitate further management. Advances in the development of biologics and allergen-specific immunotherapy will strategize the future approaches in the clinical care of respiratory allergic diseases.