BACKGROUND: Intranasal corticosteroids are one of the cornerstone treatment options for allergic rhinitis and chronic sinusitis complaints. Safety information in the summary of product characteristics may not be representative for observations in daily clinical practice. The Netherlands Pharmacovigilance Center (Lareb) collects post-marketing safety information, using spontaneous reporting systems. OBJECTIVE: Our objective was to analyse reports of adverse drug reactions associated with intranasal corticosteroids reported in the Dutch spontaneous reporting database of the Netherlands Pharmacovigilance Center Lareb to obtain insight into real-world safety data. METHODS: We retrospectively examined all adverse drug reactions of intranasal corticosteroids reported to the Netherlands Pharmacovigilance Center Lareb, entered into the database from 1991 until 1 July, 2020. RESULTS: In total, 2263 adverse drug reactions after intranasal corticosteroid use were reported in 1258 individuals. Headache (n = 143), epistaxis (n = 124) and anosmia (n = 57) were reported most frequently. Nasal septum perforation (reporting odds ratio 463.2; 95% confidence interval: 186.7-1149.7) had the highest reporting odds ratio, followed by nasal mucosal disorder (reporting odds ratio 104.5; 95% confidence interval 36.3-301.3) and hyposmia (reporting odds ratio 90.8; 95% confidence interval 45.1-182.7). Moreover, 101 (4.5%) reports were classified as serious by Lareb, including reports of Cushing's syndrome, adrenal cortical hypofunction and growth retardation. CONCLUSIONS: Many side effects are consistent with the safety information in the summary of product characteristics of intranasal corticosteroids. Several serious (systemic) side effects are reported and it is important to realise that intranasal corticosteroids may contribute to the development. Healthcare providers and patients should be aware of the potential (individual) adverse drug reactions of intranasal corticosteroids. This information could help in discussing treatment ...