Allergen-specific immunotherapy.

Specific immunotherapy was introduced for the treatment of grass pollen-induced hay fever in 1911. The treatment was soon extended to other pollens as well as perennial allergens, and to the treatment of bronchial asthma. Definitive studies of its efficacy for both rhinitis and asthma came only many decades later. Understanding gradually emerged of the underlying immunologic mechanisms that include the generation of regulatory T lymphocytes, immune deviation from allergen-specific Th2 to Th1 responses, and a shift in allergen-specific antibody production from immunoglobulin (Ig) E to IgG4. Along with understanding of the immune basis came an appreciation that immunotherapy modifies allergic disease expression, producing protection against disease progression and symptomatic improvement that persists for years after the treatment is discontinued. Recent new directions for immunotherapy include sublingual administration of inhalant allergens and use of the oral route to treat food allergy.