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What diseases cause bad breath? Causes, diagnosis, and treatment options

Welche Krankheiten verursachen Mundgeruch?

Bad breath – medically known as halitosis – is not only unpleasant for those affected, but can also become a serious social problem. While many people assume that bad breath is caused solely by poor oral hygiene or the consumption of certain foods like garlic and onions, in many cases there is a medical cause .
Persistent , strong bad breath , especially despite thorough brushing, flossing, and mouthwash, can be a sign of certain diseases . In this article, you'll learn about the underlying diseases, how they lead to bad breath, and what treatment options are available.

Why bad breath is more than just a cosmetic problem

Occasional bad breath, such as in the morning or after eating strong-smelling foods, is usually harmless. However, if the smell is persistent and intense , you should pay attention.
Medically, there are two main forms:

  • True halitosis : The smell is actually present and can be perceived by other people.

  • Pseudohalitosis : The affected person believes he has bad breath, although objectively there is none.

Around 90% of all genuine cases of halitosis originate in the mouth and throat , for example, due to bacteria on the tongue, dental problems, or inflammation . The remaining 10% are due to systemic diseases , i.e., illnesses that affect the entire body. This article addresses precisely these systemic causes.

How does bad breath arise from a medical perspective?

Most odors are caused by volatile sulfur compounds (VSC), which are formed by bacteria when proteins decompose.
Diseases can reduce saliva flow, change the oral flora, or influence the metabolism in such a way that certain unpleasant-smelling substances are excreted through the air we breathe.

For example, diabetes can cause ketoacidosis, in which breath smells fruity and sweet or like nail polish remover . In kidney failure, however, the smell is often reminiscent of ammonia or urine . Such odors can't be eliminated simply by brushing your teeth—they originate from within the body.

Diseases that can cause bad breath

1. Periodontitis and gum disease

Although periodontitis is primarily a tooth and gum disease, it is considered the most common cause of bad breath. The chronic inflammation leads to bleeding gums, the formation of pockets, and a massive bacterial overgrowth. These bacteria produce large amounts of sulfur compounds that cause a pungent odor.
The tricky part: Periodontitis is often painless and goes unnoticed for a long time until teeth become loose. Without treatment, it can even lead to tooth loss.

2. Tonsillitis and tonsil stones

Chronic inflammation of the tonsils (tonsillitis) and so-called tonsil stones (tonsilloliths) are also a common source of bad breath.
Tonsil stones are small, yellowish deposits in the hollows of the tonsils, consisting of dead cells, bacteria, and food debris. They emit an extremely unpleasant odor and can often only be removed through professional removal.

3. Chronic sinusitis

When the sinuses are persistently inflamed, purulent secretions drain into the throat. This secretion contains bacteria and protein breakdown products, which cause breath to smell strongly. The smell is often strongest in the morning, as the secretions accumulate overnight.

4. Gastrointestinal diseases

The stomach plays an ambivalent role in bad breath. Many people believe that bad breath primarily comes from the stomach, but this is rarely the case. However, it can occur with certain conditions:

  • Gastroesophageal reflux disease (GERD) : Stomach acid rises into the esophagus, causing not only heartburn but also sour breath.

  • Inflammation of the stomach lining (gastritis) or stomach ulcers caused by Helicobacter pylori : Studies show that this infection is associated with halitosis in some patients.

  • Stomach cancer : In rare cases, a tumor can cause changes in metabolism that affect breath odor.

5. Diabetes mellitus

Poorly controlled diabetes can lead to ketoacidosis , a life-threatening metabolic disorder. This produces ketone bodies that are excreted in the breath. The result is a very characteristic fruity-sweet or acetone-like odor .
Anyone who notices this smell in themselves or others should seek medical help immediately.

6. Renal insufficiency

When kidney function is impaired, waste products such as urea accumulate in the blood. These are partially excreted through the breath and lead to a urine-like or ammonia-like odor . This condition, also called fetor uraemicus , often occurs in advanced kidney failure.

7. Liver diseases

A severely damaged liver can no longer adequately break down toxins. In such cases, a typical sweetish, musty odor known as fetor hepaticus can develop. This occurs primarily in cases of liver cirrhosis or acute liver failure and is often a warning sign of impending hepatic encephalopathy.

8. Respiratory diseases

Lung diseases such as bronchiectasis , lung abscesses , or chronic bronchitis can cause a strong, foul breath odor due to bacterial decomposition in the lung tissue. Because the secretions originate deep in the respiratory tract, they cannot be eliminated through oral hygiene.

9. Metabolic diseases

Rare metabolic disorders such as trimethylaminuria ("fish odor syndrome") result in certain waste products being excreted through breath and sweat. Amino acid metabolism disorders in newborns can also produce specific breath odors.

Diagnosis – How do you find the cause of bad breath?

The assessment usually begins with a dentist or ENT specialist. A typical procedure may include:

History : duration, intensity, accompanying symptoms such as dry mouth, pain, heartburn.

Mouth and throat examination : Check of teeth, gums, tongue and tonsils.

Odor test : Subjective assessment or technical measurement of sulfur compounds.

Laboratory tests : Blood tests to check for diabetes, kidney and liver function.

Imaging : Ultrasound, X-ray or endoscopy if internal causes are suspected.

Therapy – How do you treat bad breath caused by illness?

Treatment always depends on the underlying condition. Examples:

  • Periodontitis : Professional teeth cleaning, antibacterial rinses.

  • Tonsil stones : removal of the stones, tonsil surgery if necessary.

  • Reflux disease : dietary changes, acid blockers.

  • Diabetes : Optimizing blood sugar control.

  • Kidney or liver diseases : Specific internal medicine therapy, if necessary transplantation.

It's important to note that oral care products alone only mask the smell for a short time. Permanent improvement is only possible if the cause is treated. Learn more about treatment options for bad breath here.

Prevention – What you can do yourself

Although not all causes of bad breath can be avoided, the following measures can help reduce the risk:

  • Thorough oral hygiene (teeth, interdental spaces, tongue).

  • Drink enough to prevent dry mouth.

  • Low-sugar diet to reduce bacterial plaque formation.

  • Regular check-ups at the dentist.

  • Early diagnosis of heartburn, chronic cough, or unusual breath odor.

Conclusion

Strong, persistent bad breath is more than a cosmetic problem – it can be a serious warning sign of various diseases , from tooth and gum disease to gastrointestinal problems, diabetes, kidney or liver failure .
Anyone who suffers from bad breath despite careful oral care should definitely seek medical attention. If detected early, many underlying conditions can be treated effectively – and in most cases, bad breath disappears as well.

Disclaimer:This article is intended for general informational purposes about probiotics only and should not be considered medical advice. It is not a substitute for professional medical consultation, diagnosis, or treatment."