The contributing role of specific IgE sensitization in the pathophysiology of sinonasal diseases including rhinitis, chronic rhinosinusitis (CRS), and nasal polyps is explored. Although it is estimated that sensitization to environmental allergens is present in 75% of patients with rhinitis, the role of allergy in CRS and nasal polyps is less certain. However, when atopy is present in the setting of nasal polyps, it is associated with worse quality of life and a higher incidence of asthma. Several theories have been put forth whereby inhalant aeroallergen exposure could drive the inflammatory response that occurs both in the nose and in the sinuses. Tools available to determine the presence of allergic sensitization include skin tests for immediate hypersensitivity, in vitro testing for allergen-specific IgE, and nasal allergen provocation testing. Whether by skin testing or in vitro testing, the identification of specific IgE requires clinical correlation with the history and physical exam.