The taste buds — rounded cell structures that contain nerves sensitive to taste — are concentrated mainly on the upper surface of the tongue. Sensory nerves in the tongue also respond to temperature, pain, and pressure, all of which also affect the flavor of food. The senses of smell and taste are closely intertwined, so it can be difficult to distinguish a loss of taste from a loss of smell.
A number of conditions can alter the sense of taste. In some, such as pregnancy, hormonal changes seem to increase sensitivity to certain flavors. More often, nerve or mouth disorders cause a loss of sensitivity to taste.
Causes of loss or change of taste
In this condition, which is probably due to inflammation of the facial nerve, one side of the face suddenly becomes numb and paralyzed. The symptoms may include changes in taste.
In this lung disease, the bronchial tubes become blocked with thick mucus. Along with frequent coughing and sputum production, the disorder may create a foul taste in the mouth.
Tumors in the mouth or stomach can affect the sense of taste or cause an unpleasant taste. A brain tumor that presses on nerves that carry taste messages can also cause disturbances in taste and other senses.
Many of the drugs used to treat cancer cause foods to lose their normal taste, as does radiation therapy. Many people receiving anticancer drugs also complain of a constant metallic taste in the mouth. Radiation and chemotherapy can lead to development of mouth sores and inflammation. The sense of taste may return to normal a few months after the therapy ends.
Chronic gastritis, or long-term irritation of the lining of the stomach, often causes an acid taste in the mouth, along with loss of appetite and a swollen abdomen.
Swelling, tenderness, and redness of the gum tissue around the teeth characterize
inflammation of the gums. The condition is caused by plaque, a sticky substance formed when bacteria break down food particles on the teeth. Inflamed gums bleed easily and sometimes cause a foul taste in the mouth.
A migraine headache may block the senses of taste and smell. Migraines are often preceded by visual disturbances. Nausea, vomiting, and intense, throbbing pain may also occur.
The hormonal changes of pregnancy, particularly during the first 3 months, create cravings for some foods and aversions to others. These alterations diminish as the pregnancy progresses. Cravings for substances such as clay or starch, which also sometimes develop during pregnancy, are known as pica. Pregnant women who have the urge to eat substances other than food should speak to their doctors, since they may be suffering from nutritional deficiencies.
A cold, or an upper respiratory infection, is the most frequent cause of temporary loss of taste. The nasal congestion that occurs with colds diminishes the ability to taste. Respiratory infections also cause inflammation of tissues in the throat and back of the mouth, further impairing taste. Flu, or influenza, can have similar effects.
This autoimmune disease is characterized by destruction of the exocrine glands, which
include the salivary glands in the mouth, the tear glands in the eyes, and the glands that secrete mucus in the respiratory system. The disorder causes mouth dryness, which in turn lessens the ability to taste.
Any condition that affects the tongue also impairs the sense of taste. Tongue sores, or glossitis, can have many causes, from irritation due to jagged or broken teeth to certain vitamin deficiencies or anemia. Tongue swelling and protrusion, which may be caused by a tongue injury or by a systemic condition such as an allergy or underactive thyroid, also results in impaired ability to taste.
Toothaches and abscesses
Untreated tooth decay can progress from the surface of the tooth to its internal structures, causing pain and leading to possible abscess formation. Even when an abscess is not present, tooth decay produces foul breath and an unpleasant taste in the mouth.
In trench mouth, the tissue between the teeth becomes gangrenous and dies. Its manifestations include pain, bleeding gums, and formation of a gray membrane over the infected area. Trench mouth also causes bad breath and a foul taste in the mouth.
Advice about loss or change of taste
- Practice good dental hygiene by brushing after each meal and flossing at least once a day.
- Have a dental checkup twice a year to prevent gum disease and tooth decay.