25. Immunotherapy of allergic disease.

Specific immunotherapy involves the administration of allergen extracts to achieve clinical tolerance of the allergens which cause symptoms in patients with allergic conditions. Immunotherapy has been shown to be effective in patients with mild forms of allergic disease, and also in those who do not respond well to standard drug therapy. Recent studies suggest that specific immunotherapy may also modify the course of allergic disease, by reducing the risk of developing new allergic sensitizations, and also inhibiting the development of clinical asthma in children treated for allergic rhinitis. Specific immunotherapy remains the treatment of choice for patients with systemic allergic reactions to wasp and bee stings. The precise mechanisms responsible for the beneficial effects of SIT remain a matter of research and debate. An effect on regulatory T cells seems most probable, associated with switching of allergen-specific B cells towards IgG4 production. Few direct comparisons of specific immunotherapy and drug therapy have been made. Existing data suggest that the effects of specific immunotherapy take longer to come on, but once established, specific immunotherapy will give long-lasting relief of allergic symptoms, whereas the benefits of drugs only last as long as they are continued.