Overview of Smell and Taste Disorders

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 Common Cold The common cold is a viral infection of the lining of the nose, sinuses, and throat. Many different viruses cause colds. Usually, colds are spread when a person's hands come in contact with... read more , 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 influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more (flu) virus. Some people cannot smell or taste for several days or even weeks after a bout of the flu, and rarely, loss of smell or taste becomes permanent. Sudden loss of smell may also be an early symptom of COVID-19 COVID-19 COVID-19 is an acute respiratory illness that can be severe and is caused by the coronavirus named SARS-CoV-2. Symptoms of COVID-19 vary significantly. Two types of tests can be used to diagnose... read more , an acute respiratory illness that can be severe. COVID-19 is caused by a coronavirus called SARS-CoV-2. (See Loss of Smell Loss of Smell Anosmia is complete loss of smell. Hyposmia is partial loss of smell. Most people with anosmia can taste salty, sweet, sour, and bitter substances but cannot tell the difference between specific... read more .)

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 Histrionic Personality Disorder Histrionic personality disorder is a mental health condition that is characterized by a pervasive pattern of excessive emotionality and attention seeking. People with histrionic personality... read more (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:

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.

A reduction in the ability to taste (hypogeusia) or loss of taste (ageusia) usually results from conditions that affect the tongue, usually by causing a very dry mouth. Such conditions include Sjögren’s syndrome Sjögren Syndrome Sjögren syndrome is a common autoimmune connective tissue disorder and is characterized by excessive dryness of the eyes, mouth, and other mucous membranes. White blood cells can infiltrate... read more , heavy smoking (especially pipe smoking), radiation therapy of the head and neck, dehydration, and use of medications (including antihistamines and the antidepressant amitriptyline).

Nutritional deficiencies, such as decreased zinc, copper, and nickel levels, can alter both taste and smell. Sudden loss of taste may be an early symptom of COVID-19 COVID-19 COVID-19 is an acute respiratory illness that can be severe and is caused by the coronavirus named SARS-CoV-2. Symptoms of COVID-19 vary significantly. Two types of tests can be used to diagnose... read more .

In Bell palsy Bell Palsy Bell palsy (a type of facial nerve palsy) is sudden weakness or paralysis of muscles on one side of the face due to malfunction of the 7th cranial nerve (facial nerve). This nerve moves the... read more (a disorder in which half of the face is paralyzed), the sense of taste is often impaired on the front two thirds of one side of the tongue (the side affected by the palsy). But this loss may not be noticed because taste is normal or increased in the rest of the tongue.

Burns to the tongue may temporarily destroy taste buds. Neurologic disorders, including depression Depression Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to interfere with functioning. It may follow a recent... read more and seizures Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more , may impair taste.

A distortion of taste (dysgeusia) may be caused by inflammation of the gums (gingivitis Gingivitis Gingivitis is a mild form of periodontal disease characterized by inflammation of the gums (gingivae). Gingivitis results most often from inadequate brushing and flossing but may result from... read more ) or by many of the same conditions that result in loss of taste or smell, including depression and seizures. Taste may be distorted by some medications, such as the following:

Taste can be tested using substances that are sweet (sugar), sour (lemon juice), salty (salt), and bitter (aspirin, quinine, or aloes).