Few things are more disruptive in everyday life than a dry mouth combined with unpleasant bad breath. Many sufferers find the feeling of dry mouth unpleasant, distressing, and restrictive. It's even more distressing when it also leads to bad breath – a taboo subject that can severely impair social interactions and self-esteem. However, these symptoms are rarely merely cosmetic problems. They are often the expression of a complex interplay between saliva production, the oral microbiome, and systemic factors.
In this article, we explain how dry mouth develops, why it often leads to bad breath, how the microbiome suffers as a result, and why the targeted use of probiotics is a promising therapeutic approach.
What does a dry mouth actually mean?
In medical terms, xerostomia refers to the subjective sensation of a dry mouth. This is often accompanied by an objective reduction in saliva flow (hyposalivation). However, the dry mouth sensation can also occur without a measurable reduction in saliva production.
Saliva plays a central role in oral health. It flushes away food debris, neutralizes acids, moistens the mucous membranes, and contains antibacterial substances that support the balance of the oral flora. A lack of saliva therefore has far-reaching consequences – it alters the environment in the mouth, thus promoting tooth decay, inflammation, bad breath, and an unpleasant feeling of dryness.
Causes of dry mouth
Dry mouth can have many causes. The most common are:
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Medications : Many medications, such as antidepressants, antihistamines, antihypertensives or diuretics, reduce saliva production.
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Systemic diseases : Autoimmune diseases such as Sjögren's syndrome or diabetes mellitus can lead to dry mouth.
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Dehydration and fluid deficiency : If you don’t drink enough fluids, your mouth will also dry out.
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Psychological factors : Stress, anxiety and nervousness activate the sympathetic nervous system, which inhibits saliva production.
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Radiotherapy in the head and neck area : Radiation can cause permanent damage to salivary glands.
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Aging processes : With age, the amount of saliva often decreases.
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Bad habits : Smoking, excessive alcohol consumption and mouth breathing dry out the mucous membranes.
Each of these causes negatively impacts saliva volume and quality. Less saliva means less effective oral cleansing and a changed environment for microorganisms.
Bad breath – a common symptom of dry mouth
A dry mouth is one of the main causes of bad breath (halitosis). Without sufficient saliva, bacteria can multiply unhindered. Anaerobic bacteria, in particular, which thrive in a lack of oxygen, produce volatile sulfur compounds (VSCs) such as hydrogen sulfide or methyl mercaptan – the main causes of bad breath.
Bad breath often originates in the back of the tongue, in gum pockets, or other hard-to-reach areas of the mouth where bacteria can easily colonize. A dry mouth creates an ideal environment for these odor-causing bacteria, as the cleansing and antibacterial effect of saliva is reduced.
The oral microbiome – a complex ecosystem
The mouth is home to one of the most diverse and complex microbiomes in our body. Over 700 different species of bacteria colonize the oral cavity. This microbiome is crucial for oral health.
Under normal conditions, the microbiome maintains a delicate balance. It ensures that harmful bacteria are kept in check and supports the immune system. Some bacteria are directly involved in maintaining the oral mucosa, while others help neutralize acids.
When this balance is disturbed, it is referred to as dysbiosis. Dysbiosis in the oral cavity can be triggered by various factors, including dry mouth, poor oral hygiene, antibiotic use, or illness.
How dry mouth affects the microbiome
Reduced saliva flow fundamentally changes the conditions for microorganisms in the mouth. Saliva's protective functions—including removing food debris, flushing out microbes, and providing antibacterial substances such as lysozyme or lactoferrin—are lost.
This can lead to an overgrowth of pathogenic germs. Particularly problematic are bacteria such as Porphyromonas gingivalis , Fusobacterium nucleatum , and various anaerobic species that promote inflammation and gum problems.
Studies show that in cases of dry mouth, the oral microbiome is less diverse and more susceptible to pathogenic changes. Dysbiosis not only contributes to caries and periodontitis but also exacerbates bad breath.
The role of probiotics in oral health
Probiotics are live microorganisms that, when administered in sufficient quantities, have health benefits. While they were long known primarily for their role in gut health, they are increasingly gaining attention in oral medicine.
There are now various probiotic strains specifically for the mouth that demonstrate positive effects. These include Streptococcus salivarius M18 and K12, Lactobacillus reuteri , and Lactobacillus brevis .
These probiotic bacteria can work in several ways:
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Restoring microbial balance : They eliminate harmful germs and promote a healthy microbiome.
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Production of antimicrobial substances : Bacteriocins inhibit pathogenic bacteria.
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Reduction of inflammation : Probiotics can modulate the immune response and reduce inflammation in the mouth.
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Stimulation of saliva production : Some studies suggest that certain probiotics can stimulate salivary gland function.
Scientific studies on probiotics for dry mouth and bad breath
Numerous studies support the benefits of oral probiotics for symptoms of dry mouth and halitosis. In clinical trials, probiotics have significantly reduced the sulfur odor and improved the microbiological composition of the oral cavity.
A study with Streptococcus salivarius M18, for example, showed that regular intake of lozenges reduced colonization with pathogenic bacteria and stabilized the oral flora. Saliva production was also increased in some subjects.
Further studies show that probiotics can reduce the incidence of gingivitis and caries – typical consequences of a disturbed oral environment caused by dry mouth.
Practical tips to support the microbiome in cases of dry mouth
In addition to the targeted use of probiotics, the following measures also help to strengthen the oral microbiome and alleviate symptoms:
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Drink enough to promote saliva production.
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Oral hygiene with microbiome-friendly products that do not contain harsh chemicals.
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Regular tongue cleaning to reduce bacterial plaque on the surface of the tongue.
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Avoid mouthwashes containing alcohol , as they can dry out and disrupt the microbiome.
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Avoid smoking and excessive alcohol consumption , which have a negative effect on the oral environment.
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Stress reduction , as stress reduces saliva secretion and weakens the immune system.
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Regular dental check-ups to detect diseases early.
How are probiotics used?
Oral probiotics are available in the form of lozenges, capsules, mouth sprays, or yogurts. For oral health, specially formulated products are available that release the probiotic bacteria directly into the mouth.
