Allergen immunotherapy (AIT) is used for the control of allergic diseases that are not completely responsive to avoidance strategies and/or pharmacotherapy. It is also considered the main treatment with the potential to modify allergic disease evolution. It's efficacy and safety in allergic rhinitis and asthma is supported by large systematic reviews and is recommended as a cornerstone treatment option in allergic disease. Molecular based allergy diagnosis has greatly evolved and the knowledge of molecular allergen sensitization pattern has been used to better define the allergen extract composition of AIT. However, uncertainty remains if this strategy is related to an increase of efficacy. Regulation of allergen extracts for allergen immunotherapy are currently underway in Europe, but there is still lack of standardization of relevant allergens and important differences are seen between allergenic contents. Therefore, we aim to evaluate, in a real-life setting, the impact of using molecular-based diagnosis versus standard diagnostic tools in the efficacy of aeroallergen immunotherapy, using a pragmatic randomized controlled trial design and also to address the impact of the discrepancy between individual aeroallergen sensitization profiles and the major allergen molecular content of aeroallergen immunotherapy.