What is Flonase? Flonase is a nasal spray containing fluticasone. Fluticasone is corticosteroid that prevents the release of substances in the body that cause inflammation. Flonase nasal spray is used to treat nasal congestion, sneezing, runny nose, and itchy or watery eyes caused by seasonal or year-round allergies. Flonase nasal spray is for use in adults and children who are at least 4 years old. Flonase is available without a prescription.