Duration of allergen immunotherapy for inhalant allergy

Purpose of review We evaluated the time-course of clinical and immunologic changes that occur during and after cessation of sublingual and subcutaneous allergen immunotherapy for inhalant allergies. Recent findings Increases in production of inhibitory cytokines, such as IL-10 and allergen-specific IgE and IgG(4) antibodies are induced within weeks of starting immunotherapy for both seasonal and perennial allergens. In general, 2-4 months' immunotherapy is needed for onset of efficacy whereas maximal clinical effect is achieved within 1-2 years of treatment. Therefore, assuming optimal patient selection, good compliance and at least moderate allergen exposure, if immunotherapy is ineffective at 2 years, it is reasonable to discontinue the treatment. For long-term clinical efficacy, at least 3 years of either subcutaneous or sublingual immunotherapy is required and this results in clinical and immunologic tolerance -- persistence of clinical benefits and suppression of type 2 immunity for years after discontinuation of treatment. Both sublingual and subcutaneous immunotherapy are effective and well tolerated for respiratory allergy. Clinical and immunological changes occur at early stages of treatment. Long-term evaluations support recommendations in international guidelines that both routes of administration should be continued for a minimum of 3 years to achieve disease modification and long-term tolerance.