What is a bitter taste in the mouth? A bitter taste in the mouth that is not from a bitter substance is a distorted sense of taste. A persistent bad taste in the mouth, whether bitter, metallic or foul, is called dysgeusia. A lack of, or change in, taste often occurs when something interferes with the normal taste process. Your sense of taste and the flavors you perceive are the result of a combination of the sense of smell and sensory neurons in your taste buds, which tell the brain what substances you taste. The taste buds are able to identify sweet, salty, sour and bitter tastes. Some people are more sensitive to bitter tastes because they can taste a bitter compound called phenylthiocarbamide (PTC), which other people either do not taste at all or taste only moderately. A person is born with about 10,000 taste buds, although this number shrinks with age. That is why older people can usually tolerate more intense tastes than children. Common causes of a bitter taste in the mouth include vomiting and acid reflux, although these conditions do not generally cause a permanent bitter taste. Pregnancy or taking certain medications, such as antibiotics, may result in a temporary bitter taste in the mouth as well. Your sense of taste can also be impaired or distorted permanently from long-term smoking or injuries to the mouth, nose or head. Because a bitter taste in the mouth can be a sign of an infection or other condition, you should seek prompt medical care and talk with your medical professional about your symptoms. If the bitter taste persists, recurs, or causes you concern, notify your health care provider. Seek immediate medical care (call 911) if you have trouble breathing or swallowing.