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In approximately 90% of the cases of genuine halitosis, the origin of the bad odor is in the mouth. Most of these cases are due to gum disease (gingivitis or periodontitis), followed by the presence of caries, oral cavity infections (viral or bacterial), the presence of candida, ulcers and to a lesser degree systemic diseases with oral involvement. The remaining 10% is attributed to side effects of diseases or medical treatments.

When the origin of bad odor is in the mouth, what is the cause?

1. Poor oral hygiene

Poor oral hygiene is a predominant factor in most of these cases. Failure to brush and floss regularly allows bacteria to accumulate and produce bad odor. Incorrect hygiene of fixed or removable dentures.

2. Dry mouth

During the night, saliva production decreases significantly, allowing foul-smelling gas-producing bacteria to multiply. This phenomenon is known as morning breath and can be corrected with good daily oral hygiene.

3. Age

With aging, the salivary glands produce less saliva, which increases the likelihood of cavities and other oral diseases.

4. Smoking and alcohol

Tobacco consumption is another factor that increases the risk of halitosis as well as alcohol.

5. Diet

Low-calorie diets and skipping meals may contribute to bad breath due to decreased saliva production and changes in metabolism. Also diets that vary pH.

6. Specific foods

In addition, certain foods such as onions and garlic can cause strong, persistent breath, although this is temporary and resolves after a few hours.

When the reason is not in the mouth, what is it?

1. Diseases and tooth decay

In this group of people, halitosis can be a consequence of periodontal diseases and tooth decay.

2. Infections

It can also be the result of ulcers, viral, bacterial or fungal infections. Dental abscesses.

3. Medical treatments

Cancer treatments such as radiotherapy and chemotherapy can also have halitosis as a side effect.

4. Other diseases

Sometimes, bad breath can be a symptom of digestive diseases (reflux, vomiting, gastric ulcers…) respiratory (such as sinusitis) or systemic, such as poorly controlled diabetes mellitus, incipient kidney disease or liver dysfunction…


Halitosis can be an indication of our oral and general health. If you suspect the presence of halitosis, it is advisable to see your doctor or dentist – we are here to help you maintain optimal oral health!

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