The allergist's community has recently celebrated 100 year of Allergen Immunotherapy (AIT). Unfortunately the implemention of this treatment is still impaired by some challenges. With the diversity of definitions, methodology and different allergen products used, research studies have produced conflicting outcomes. This has resulted in confusion about the benefits and risks of AIT amongst policymakers and professionals, as well as in the variable availability of AIT products, regulation and reimbursement policies globally. In 2015 EAACI initiated the AIT Guidelines project as part of the Presidential plan in order to settle the controversies. This article is protected by copyright. All rights reserved.