The first step in diagnosing anosmia is a physical exam that includes a review of your medical history. Your doctor will also test your sense of smell. He or she will place a variety of substances beneath each of your nostrils and then you will be asked to determine the source of the fragrance. Any blockages or infections hindering the nasal passage will be checked for. To check for malformations (including tumors or fractures) around the nasal cavity, your doctor may perform more specialized tests, such as a computed tomography (CT) or magnetic resonance imaging (MRI) scan, if the origin for anosmia is still not found.