Anosmia is the lack of a sense of smell . The incidence of anosmia from all causes among the general population ranges from 2 percent to 20 percent. Lacking the sense of smell, even temporarily, can be serious. It can affect all aspects of a person’s life, including physical health and social and emotional well-being.
A small number of people are born with anosmia, but it is usually acquired during the course of one’s lifetime. Sinus infection, allergies, and nasal polyps (growths inside the nose ) rank as the most common causes of anosmia. Polyps can block the nasal passages, preventing the detection of odors. People usually regain a normal sense of smell when these conditions are treated.
Anosmia can also result from head injury. In such instances, the loss of smell is usually permanent. A blow to the head may, for example, damage or move the cribriform plate. The cribriform plate consists of a thin layer of bone perforated with tiny holes just above the nasal cavity. Jarring the cribriform plate may tear olfactory nerve endings, which pass through the holes. Olfactory nerves convey sensory information about smell from the nasal cavity to the brain . Injury may also cause scarring that blocks the holes. Nerve fibers carrying sensory information cannot reach the brain, preventing the perception of scents.
People may lose their sense of smell as they age. The rate and severity of smell loss varies from person to person. Unlike that caused by illness or injury, smell loss from aging is gradual and often unnoticed. It can lead to poor nutrition and other health consequences. The perception of flavor includes smell along with other sensations associated with food (see Taste ). People with smell loss may thus miss cues to eat. They may also try to compensate for loss of flavor with excess salt or other additives.
Health care professionals recognize that loss of the sense of smell can be an early symptom of some neurological disorders. These disorders include Parkinson disease and Alzheimer’s disease . People with these conditions may notice difficulty identifying familiar odors long before any other symptoms appear. Medical experts therefore recommend that people who experience smell loss consult a doctor.
See also Smell .
