Can Your Mouth Bacteria Cause Hearing Loss?

Sam Westreich, PhD

“Your mouth microbiome might be threatening your hearing!” “What?”

Despite what you may have seen in childhood cartoons, your head is not hollow. We cannot shine a flashlight into one ear and out the other — and no matter how hard you take a drag on a cigarette, you won’t get smoke wafting out through your ears.

But there may be some connection between the bacteria in our mouth, and the health of our ears. And it comes down to our spit — and our oral hygiene habits.
“Sorry, I can’t hear you, my mouth is full.”Photo by Diana Polekhina on Unsplash

Interestingly, there are two different theories about how oral bacteria may impact our hearing. They aren’t exclusionary — just because one is correct, the other may still also be true.

The first theory involves blood infections.

The second theory involves saliva in the air.

Let’s take a look!

“Such a bad infection, it made him deaf”

The first theory for the interplay between oral bacteria and hearing ability has an important intermediate step to recognize: widespread infection.

This theory puts forth that, when someone doesn’t have good oral hygiene, the bacteria can proliferate and can lead to periodontal diseases and abscesses, giving them easy access to the bloodstream.

Once bacteria are in the bloodstream, they trigger widespread inflammation, as the immune system goes on high alert to stomp out the invaders. This inflammation helps fight off the invading bacteria, but it also reduces blood flow to many areas, including to the inner ear.

Inside our inner ear (also known as the cochlea), tiny hair cells detect vibrations, converting them into signals that are passed to the brain for interpretation. If those super-sensitive hairs are damaged, we lose hearing. And reduced blood circulation can damage the cells around these hairs that sense noise.

So the disease progression looks like:

Bad oral health -> bacteria enter bloodstream -> inflammation -> hearing loss

Interestingly, while each of these steps has been shown in scientific papers, I haven’t seen any papers that link them all together.

Oral microbiota in human systematic diseases — Oral bacteria are, in some cases, able to break through the barriers and enter the bloodstream, where they can cause a host of issues, including inflammation.

A risk scoring system for predicting Streptococcus suis hearing loss: A 13-year retrospective cohort study — We also see that inflammation (in this case caused by bacterial meningitis) can lead to hearing loss.

But the full link doesn’t appear to be widely published. Is bacterial infection from oral bacteria (periodontitis) significant enough to cause hearing loss?

The question may still be unanswered, but you probably don’t want to find the answer out yourself.

“Don’t spit in the air, you’ll make me go deaf”

A common childhood disease is otitis media with effusion (OME), a complex name for the accumulation of fluid in the middle ear. It’s not specifically linked with a certain bacteria infecting the ear, since there’s not a ton of inflammation, but it is a serious condition. It can lead to significant hearing loss, which is bad for younger children because this is at the period where they need to learn the most.

OME is often treated surgically, with insertion of tubes to drain the fluid. Ideally, we’d like to find the cause behind OME, to take preventative actions so we don’t need to intervene with surgery on young children.

Examination of the fluid in OME reveals there is often (although not always) the presence of bacterial DNA. The DNA matches a few different bacteria, including Streptococcus pneumoniae, Haemophilus influenzae, Fusobacterium nucleatum, Treponema denticola, and Moraxella catarrhalis.

How could these bacteria get into the middle ear?

One leading theory: saliva and the oral microbiome! All of these bacteria can be found in the mouth and nose. F. nucleatum and T. denticola, in particular, are anaerobic (oxygen-hating) and tend to be found in the upper nose of young children.

So are these children managing to get spit into their ears?

Possibly, but the more likely route is through a connection called the Eustachian tube. This tube connects the middle ear with the nasal passage. It’s important for helping to equalize the pressure in the middle ear, and also helping to drain any fluid. It may be the highway that bacteria take in young children to get into the middle ear where they cause fluid buildup.

OME was previously treated with antibiotics, but current experiments are focusing more on probiotics, providing good bacteria to out-compete the pathogenic bacteria typically associated with OME.
See that Eustachian tube going down? That connects to the nose — and could let bacteria up into the ear.Wikipedia

Should I be worried about oral bacteria causing ear problems?

What’s the takeaway here? As an everyday individual, how much concern should I have about the bacteria in my mouth leading to any ear problems?

For most of us who keep up on our oral health, we don’t have much to fear. The main threat for adults is if bacteria start getting into our bloodstream through lesions or advanced gum disease, causing a strong immune response that leads to other nasty secondary effects on the rest of our bodies.

Keep your mouth clean and tidy enough to avoid letting the happy oral bacteria into the bloodstream? You shouldn’t get blood infections, and thus keep your cochlear hairs safe.

Otitis media with effusion (OME) is likely caused by mouth and nose bacteria migrating up to the ear, but it’s more common in children. The best recommended treatments for preventing OME include vaccinating against viral diseases like influenza, and breast feeding infants to encourage a more robust, preventative microbiome.

It’s fascinating to see how connected our different systems are, how imbalances in our microbiome can spill over to cause issues in other areas. Our oral microbiome is fine inside our mouth, but can cause issues in other parts of our body if the bacteria break out.

A place for everything, and everything in its place — including our bacterial partners!

Enjoyed the story? Consider sharing it on Twitter — you can tag me @swestreich with your thoughts.

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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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