“Anosmia” is the technical term for the loss of smell (as well as taste) that runs even when there is no obvious cause, e.g. fever. Anosmia is the most common consequence of chronic conditions, e.g. allergic rhinitis or nasal polyps. In rare cases anosmia is a symptom of a brain tumor or a result of head injuries in which olfactory nerves are severed (nerves that go from the top of the nasal meatus and transmit sensations of smell from the nose to the brain).
What to do?
If you have lost your sense of smell and taste, consult a doctor who will probable discover that it is a disease of the nose that can be treated, and thus curing anosmia. If there are no signs of abnormalities in the nose, the doctor will refer you to a neurologist who will perform various diagnostic tests. Olfactory nerves may not be damaged; however, if they are, it won’t be treated easily.