This review examines the possible causative relationship between allergic rhinitis (AR) and chronic rhinosinusitis (CRS) that has long been proposed. Many observational and experimental studies exist, however no clear and definitive connection has been established. This is mainly due to great diversity in study methodology. For this reason, the authors applied the revised Bradford-Hill guidelines to relevant studies, aiming to answer the question “is AR a predisposing factor for CRS?”. Despite the ‘unified airway’ concept, multiple pathophysiologic mechanisms seem to be involved that are not common in both clinical entities. This review identifies that there is a lack of consistency in the terms used to define AR and CRS, which undermines the strength of the association. The authors conclude that no clear and definitive causal relationship can be established, especially in children. It is also suggested that any CRS patient with uncontrolled symptoms should be evaluated for underlying allergies. The authors appropriately reinforce this principle, also supported by the Joint Task Force on Practice Parameters (JTFPP) document, Clinical Practice Guideline: Adult Sinusitis (CPG:AS), The British Society for Allergy & Clinical Immunology (BSACI) and European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) guidelines.