What Is the Oral Microbiome?

What is the oral microbiome, exactly?

The oral microbiome is the collection of bacteria, fungi, viruses and other microbes that live throughout your mouth, including on your teeth, gums, tongue, cheeks and in your saliva. After the gut, the mouth houses the body’s second most diverse microbial community, with more than 700 bacterial species detected in the oral cavity. Like your gut microbiome, your oral microbiome is unique to you, shaped by factors such as genetics, diet, oral hygiene and lifestyle, so no two people’s are exactly alike.

What does the oral microbiome do?

Your oral microbiome does far more than sit in your mouth. Its main roles include:

• Protecting your mouth: A balanced microbial community helps keep disease-promoting bacteria in check
• Starting early digestion: Saliva helps start digestion, while oral microbes take part in early chemical processes in the mouth, such as nitrate conversion
• Maintaining pH balance: A balanced oral microbiome helps neutralise acids and prevent the mouth from staying too acidic, which helps protect tooth enamel
• Supporting wider health: Because the mouth connects to the digestive tract and bloodstream, oral microbiome imbalance has been linked with health beyond the mouth, including cardiovascular and gut-related pathways

When these functions work smoothly, your mouth stays healthy and the effects reach further than you might expect.

Where does the oral microbiome live?

Your oral microbiome lives all over your mouth, but different areas host different communities. The surfaces of your teeth, the gum line, your tongue, the roof of your mouth and your saliva each support their own mix of microbes suited to that environment. This is why oral health is not just about your teeth: the whole mouth is a connected ecosystem shaped by factors like pH, saliva, oxygen levels and available nutrients. The mouth is also the entry point to the digestive tract, so oral microbes can interact with the gut and wider body, although the relationship is complex.

What is a healthy oral microbiome?

A healthy oral microbiome is balanced and diverse, with a wide range of beneficial microbes helping keep disease-promoting bacteria in check and supporting a more stable oral pH. In this balanced state, your mouth is better able to support fresh breath, healthy gums and protected teeth. When the balance shifts, known as oral dysbiosis, disease-promoting bacteria can become more dominant, increasing the risk of problems like bad breath, gum disease and tooth decay.

→ 7 Signs of an Unhealthy Oral Microbiome (and What They Mean)

How does the oral microbiome form and change?

Your oral microbiome begins forming shortly after birth and develops as you grow. Birth, feeding, tooth eruption, diet and oral hygiene all help shape it over time. It can also continue to shift throughout life in response to what you eat and drink, how you care for your teeth, smoking, medications, stress and changes in saliva. This is why your mouth’s microbial balance can change with your habits, for better or worse.

Why does the oral microbiome matter for your health?

The oral microbiome matters because its balance affects more than your mouth. A healthy oral microbiome supports fresh breath, strong teeth and healthy gums, while oral dysbiosis has been linked with wider health concerns, including cardiovascular and neurological conditions. These links are complex and do not mean the oral microbiome is the sole cause, but they show why oral health is part of overall health.

→ How to Improve Your Oral Microbiome: The Complete Guide

How do you know what your oral microbiome looks like?

The only way to know your own oral microbiome is to test it, because everyone's is different. An oral microbiome test analyses a sample to show which microbes are present and how balanced your mouth is, giving you a clearer picture of your oral health as a starting point rather than guesswork.

→ Explore the Oral Microbiome Test
→ What Causes an Unhealthy Oral Microbiome?
→ The Link Between Gum Health and Heart Health
→ Oral-Gut Axis: How Oral Health Affects Your Gut