Allergic Aspergillus sinusitis is a type of allergic fungal sinusitis (AFS), a form of chronic rhinosinusitis with pathological findings similar to those seen in allergic bronchopulmonary aspergillosis (ABPA). There are no evidence-based criteria for diagnosis or management, and the pathogenesis is unknown. Known risk factors are underlying chronic rhinitis, exposure to Aspergillus fumigatus, and the ability to make an IgE-mediated allergic response to that organism. While many individuals meet these conditions, it is not known why only some go on to develop allergic Aspergillus sinusitis. Speculative risk factors are unknown conditions permitting fungal growth, concomitant superantigen responses, and HLA associations.