Duration of allergen immunotherapy for inhalant allergyPenagos, Martin; Durham, Stephen R.Current Opinion in Allergy and Clinical Immunology: December 2019 - Volume 19 - Issue 6 - p 594–605 doi: 10.1097/ACI.0000000000000585 IMMUNOTHERAPY AND NEW TREATMENTS: Edited by Giovanni Passalacqua and Robert Bush Buy Abstract Author InformationAuthors Article MetricsMetrics 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 IgG4 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. Summary 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. Allergy and Clinical Immunology, Division of Respiratory Science, Imperial College London and National Heart and Lung Institute, Royal Brompton Hospital. Dovehouse Street, London, United Kingdom Correspondence to Professor Stephen R. Durham, Allergy and Clinical Immunology, Division of Respiratory Science, Imperial College London and National Heart and Lung Institute, Royal Brompton Hospital. Dovehouse Street, London, SW3 6LY, United Kingdom. Tel: +44 (0) 207 351 8024; e-mail: email@example.com Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.