Allergen immunotherapy (AIT) is an effective treatment for allergic rhinoconjunctivitis (AR) with or without asthma (1-12). AIT has disease modifying properties and confers long-term clinical benefit after cessation of treatment (6, 7, 13-17). AIT is routinely used in daily practice and can be administered either subcutaneously (SCIT) or sublingually (SLIT) (3-12). Although AIT is effective, the degree of remission strongly varies depending on the complex interaction between patient, allergy, symptomatology and vaccines used for AIT (3-9). Clinical management of patients receiving AIT and efficacy in randomised controlled trials for drug development could be significantly enhanced if there were means to identify those who are most likely to respond, when to stop treatment, how to predict relapse and when to perform booster AIT. Furthermore, biomarkers in AIT can play a central role in personalized medicine (18). This article is protected by copyright. All rights reserved.