ear, nose, and throat disorders
Overview of Smell and Taste Disorders
Smell
The ability to smell can be affected by changes in the nose, in the nerves leading from the nose to the brain, or in the brain. For example, if nasal passages are stuffed up from a Common Cold , the ability to smell may be reduced because odors are prevented from reaching the smell receptors (specialized nerve cells in the mucous membrane lining the nose). Because the ability to smell affects taste, food often does not taste right to people with a cold. Smell receptors can be temporarily damaged by the Occasionally, smell and taste disorders are due to a serious disorder, such as a tumor. Because the ability to smell and taste decreases as people age, older people may eat less and become undernourished. After age 50, the ability to smell and to taste gradually begins to decrease. The membranes lining the nose become thinner and drier, and the nerves involved in smell deteriorate. Older people can still detect strong odors, but detecting subtle odors is more difficult. As people age, the number of taste buds also decreases, and those that are left become less sensitive. These changes tend to reduce the ability to taste sweet and salt more than the ability to taste sour and bitter. Thus, some foods start to taste bitter. Because smell and taste are diminished as people age, many foods taste bland. The mouth tends to be dry more often, further reducing the ability to taste. Also, many older people have a disorder or take medications that contribute to dry mouth. Because of these changes, older people may eat less. Then, they may not get the nutrition they need, and if they already have a disorder, their condition may worsen. Oversensitivity to smell (hyperosmia) is much less common than loss of smell. Pregnant women commonly become oversensitive to smell. Hyperosmia can also be psychosomatic. People with psychosomatic hyperosmia have no apparent physical disorder. Psychosomatic hyperosmia is more likely to develop in people who have a Histrionic Personality Disorder (characterized by conspicuous seeking of attention with dramatic behavior). Some disorders can distort the sense of smell, making innocuous odors smell disagreeable (a condition called dysosmia). These disorders include the following: Infections in the sinuses Partial damage to the olfactory nerves Poor dental hygiene Mouth infections Depression Viral hepatitis, which may cause dysosmia that results in nausea triggered by otherwise inoffensive odors Nutritional deficiencies Seizures originating in the part of the brain where memories of smell are stored—the middle part of the temporal lobe—may produce a brief, false sensation of vivid, unpleasant odors (olfactory hallucinations). These odors are part of the intense feeling that a seizure is about to begin (called an aura) and do not indicate a smell disorder. Brain infections due to herpesviruses (herpes encephalitis) may also cause olfactory hallucinations. 