Taste changes may include the complete loss of taste (ageusia), partial loss of taste (hypogeusia), a distorted sense of taste (dysgeusia), such as a metallic taste, or an unpleasant or revolting taste (cacogeusia)

A decrease in or loss of taste is common in older adults. It is part of the normal aging process and may be caused by:

• A decrease in the number of taste buds.
• Changes in the way the nervous system processes the sensation of taste. This may cause a decline in the awareness of taste.
• A decreased amount of saliva or an increased stickiness of saliva.
• Changes in the tongue, making it harder for flavors to reach the taste buds.

Other factors that may cause taste change include:

• A dry mouth.
• Loss of smell. Much of what is thought of as taste is actually smell.
• Minor infections, such as a cold or flu.
• Cigarette smoking or the use of smokeless (spit) tobacco.
• Medication or surgery. Medications that commonly distort taste include thyroid medications, captopril, griseofulvin, lithium, penicillamine, procarbazine, rifampin, vinblastine, and vincristine.
• Nutritional deficiencies of zinc or vitamin B12.
• Injury.
• Certain diseases, such as Alzheimer's disease, Bell's palsy, hepatitis, Sjögren's syndrome, and oral cancer.