Objectives To address concerns related to the safety profile of both Food and Drug Administration (FDA)–approved and non–FDA-approved intranasal corticosteroid (INCS) use in the adult population. Data Source Systematic review of MEDLINE, PubMed, and EMBASE databases using a comprehensive search strategy including all INCS formulations and adverse events. The study design was developed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Additional sources were identified from study references of relevant articles. Review Methods A structured literature search was conducted. Each study was graded for level of evidence using the Oxford Centre for Evidence-Based Medicine. Extracted data included population size, study design, drug (dosage, route, and frequency), presence of hypothalamus pituitary axis suppression, ocular symptoms, and treatment-related adverse events. Results A total of 60 studies met inclusion criteria. The studies included use of INCS as metered nasal sprays, drops, injections, aerosols, and irrigations. There were no persistent abnormalities in cortisol level or intraocular pressure change. Meta-analysis of epistaxis showed a significantly increased risk in the FDA-approved treatment group in comparison with control (risk ratio 1.56; 95% confidence interval, 1.13-2.14; P = .007). Conclusions Overall, it appears that the use of both FDA and published non-FDA application of INCS are safe in the adult population. Meta-analysis demonstrated an increased risk of epistaxis in patients using INCS compared with placebo. Otherwise, there was no significant difference between in adults in the treatment group and placebo group. As an important caveat, the interpretation of safety of nonstandard INCS is restricted to delivery methods and dosages published in the literature.