We reviewed the evidence for the benefits and harms of adding a short course (typically up to 14 days) of corticosteroid given by mouth to people with chronic rhinosinusitis who were also receiving another type of treatment (such as corticosteroids delivered through the nose). Background: Chronic rhinosinusitis is a common condition that is defined as inflammation of the nose and paranasal sinuses (a group of air-filled spaces behind the nose, eyes and cheeks). Patients with chronic rhinosinusitis experience at least two or more of the following symptoms for at least 12 weeks: blocked nose, discharge from their nose or runny nose, pain or pressure in their face and/or a reduced sense of smell (hyposmia). Some people will also have nasal po...