When Bad Breath Indicates A Disease

Bad breath is embarrassing for many. Bad breath can be a symptom of serious illness. How can you tell which disease is behind bad breath?

Bad breath can have various causes. They are usually harmless and can be remedied by thorough dental hygiene. But behind bad breath can also be serious diseases. We asked Professor Uwe Heemann from the Department of Nephrology at the Klinikum rechts der Isar at the Technical University of Munich which diseases are involved and what smell they have.

Main cause lies in the mouth or throat area

In up to 90 percent of all cases, the cause of bad breath lies in the mouth or throat. Bad breath is usually caused by bacteria in the interdental spaces that release sulphur when saliva or food remains are decomposed. They can lead to gum inflammation and large caries holes, which in turn spread bad odors.

Therefore, brushing your teeth incorrectly is a major cause of bad breath. To avoid this, the interdental spaces should be cleaned regularly with dental floss or interdental brushes as well as with a toothbrush. Also plaque from the tongue should be removed.

Tonsillitis smells rotten

If bad breath persists despite brushing your teeth and a dental examination does not show any results, there may be a disease behind bad breath that needs to be treated by an internist or ENT doctor.

For example, tonsillitis, pharyngitis or sinusitis can be considered. Professor Heemann explains: “Chronic tonsillitis leads to a typical bad breath. It is caused by bacteria that settle in the deep, small cavities of the tonsils”.

Bad breath due to diabetes

Sometimes bad breath can also indicate an acute disease. According to Heemann, a fruity bad breath – also known as ketone smell – indicates an undiscovered or poorly controlled diabetes mellitus.

“This smell helps a patient in the emergency room to recognize that he is a diabetic with insulin deficiency,” says the internist. But the fruit-like smell can also be the result of an eating disorder or can be caused by prolonged fasting. Then it helps to eat something to eliminate bad breath.

Kidney disease can be recognised by the breath

According to Heemann, a breath smelling of urine or ammonia can be an indication of kidney weakness or even kidney failure. “This is due to the excessive urea content in the body,” says the expert. Normally, the kidneys excrete these substances through the urine. But when the kidney no longer functions properly, the pollutants enter the bloodstream and are exhaled via the lungs.

Lung diseases also sometimes manifest themselves through bad breath, for example when abscesses in the lungs lead to a foul smell of the breath. For example, at a certain stage, specialists can smell whether a patient has lung cancer. According to Professor Heemann, however, such diagnoses are very rare.

Typical sour smell in gastric disorders

“Diabetes and kidney disease are the two most common diseases to be detected by bad breath,” says the expert. “The sour smell of stomach ailments is also relatively typical. This is the case when inflammation of the gastric mucosa or tumours in the oesophagus or stomach cause liquids or malodorous gases to enter the oral cavity.

“But smells play a subordinate role these days,” explains Heemann. Laboratory tests and medical devices have largely replaced olfactory diagnostics. “But in rural medical practices with little technical equipment, diagnosis by smell is still a common and helpful method.


Bad breath is extremely unpleasant – especially for others. Many people do not even notice that they smell badly from their mouths. If the other person distorts his face and keeps his distance during the conversation, this is an indication that bad breath is the reason. Sometimes a friendly person gives a discreet hint of bad breath. In the worst case, bad breath makes people very lonely and drives them into social isolation.

Dentists estimate that about five percent of the German population always have bad breath. This is called chronic bad breath. About 25 percent of German citizens do not have bad breath all the time, but at least temporarily feel that their bad breath is a problem. In medical terms, bad breath means “halitosis” or “foetor ex ore”.

The bad smell is not only noticeable in the breathing air from the mouth, but also when exhaling through the nose. Anyone who suddenly develops bad breath after eating has usually eaten a food that tastes intense, but also smells accordingly, for example onions or garlic.

Even brushing your teeth afterwards can sometimes not eliminate extreme bad breath. It can last for hours or even days. A common misconception is that bad breath is caused by the gastrointestinal tract. It is known today that the reason for bad breath is to be found in about 90 percent of patients in the oral cavity or in the nasopharyngeal cavity. This is often due to poor oral hygiene or problems with the tonsils.

What to do about bad breath

If there is no disease behind the bad breath, you can often get rid of bad breath if you follow a few tips:

  • Brush your teeth thoroughly twice a day. Don’t forget to brush your tongue.
  • Also use dental floss or interdental brushes.
  • Drink plenty of water or unsweetened teas. A dry mouth can promote odour.
  • A mouth rinse with sage tea also reduces odour.

If you are unsure where your bad breath comes from or if it persists despite these measures, consult a doctor to be on the safe side.