Conditions that affect the nose and sinuses The openings of the nose to the outside world are the two small nostrils. While for many people all the air that is breathed comes through the nostrils, the nostrils seem to be too small for this purpose for other people. People who are regular mouth breathers are more likely to develop throat illnesses and less likely to rely on smell. The medical term for inability to smell is anosmia. Most of the time this condition is temporary and caused by blocked nasal passages as a result of the common cold or allergies .
Brain injury can affect the part of the brain connected with smell, known as the olfactory center.
Fear of a particular odor is sometimes suggested as a cause of anosmia. The center section of the nose, between the two nostrils, is called the septum. If it is congenitally shifted to one side, or if it becomes shifted as a result of injury, it is said to be deviated. This condition, which can usually be corrected by surgery, interferes with normal breathing and causes nasal passages to block more readily. Nasal polyps Sometimes the mucous membrane can thicken and protrude into the air passages.