Background: Hereditary angioedema (HAE) is an autosomal-dominant disorder resulting from C1-inhibitor (C1INH) deficiency. Smell impairments were found in patients affected with systemic lupus erythematosus, that, similarly to HAE, is characterized by the activation of the classical complement pathway with C4 consumption. In this study, we aimed at evaluating the sense of smell in patients with HAE. Methods: Thirty patients with HAE and 30 healthy age- and sex-matched controls were evaluated for olfactory functions using the 3-stages Sniffin’-Sticks kit (threshold, discrimination, and identification [TDI]). TDI scores were analyzed according to complement levels (C1INH, C3, C4 and CH50), Beck depression inventory (BDI-II) and danazol treatment. Results: A significant decrease in olfactory function was observed in patients affected with HAE compared with controls in total TDI score (P