The role of allergen immunotherapy in asthma management

Immunotherapy (IT) using extracts of inhalent allergen has been used worldw ide for more than 75 years in the management of allergic respiratory disord ers including asthma, Good clinical results with IT depend on careful patie nt selection and the use of standardized, high-quality extracts that have o nly become widely available in the last 20 years. The immunologic and clini cal consequences of effective IT include "desensitization" of antigen-drive n IgE-dependent mast cell activation, attenuation of specific T cell respon ses, and down regulation of inflammatory cells and cytokines in the respira tory mucosa, all leading to reduced end-organ responsiveness to the treatme nt allergens. Many controlled clinical trials support the effectiveness of IT in reducing upper airway symptoms and antihistamine use in allergic rhin oconjunctivitis, Effectiveness in controlling symptoms of allergic asthma h as been more difficult to demonstrate, especially in multiply sensitive per ennial asthmatics with moderate or severe disease. The risk of fatal anaphy laxis from IT treatment in the United States is apparently very low, but th ree quarters of these fatalities occur in asthmatic patients. Recent eviden ce suggests that the risk is greatest and the benefit is minimal for perenn ial persistent asthmatics requiring inhaled or oral steroids. Whether IT ca n be uniquely helpful in preventing the emergence of allergic asthma in hig h-risk, atopic children remains to be determined.