Our nose does more than help us smell—it may also be a hidden gateway into the brain. A recent study from Griffith University has uncovered that certain bacteria can travel directly from the nose into the brain, possibly triggering changes linked to Alzheimer’s disease. This finding sheds new light on how infections might play a role in the development of this serious condition.
The study, led by Professor James St John and published in Scientific Reports, focused on a type of bacteria called Chlamydia pneumoniae. This bacteria is usually known for causing respiratory infections, but the researchers discovered it can also sneak into the brain through the olfactory nerve—the nerve responsible for our sense of smell.
Unlike most areas of the body, this nerve is directly exposed to the outside air and provides a shortcut into the brain, bypassing the blood-brain barrier that normally protects the brain from harmful invaders.
Using mice in their experiments, the scientists showed that the bacteria entered the brain through the olfactory nerve and triggered a reaction. The brain’s response was to deposit amyloid beta protein—one of the key markers found in the brains of people with Alzheimer’s disease.
These sticky proteins can build up and form plaques, which are believed to interfere with brain function and lead to memory loss and other symptoms of Alzheimer’s.
The researchers also pointed out a surprising everyday risk: nose picking and plucking nose hairs. These common habits can damage the inside lining of the nose, making it easier for harmful bacteria to enter the body—and possibly the brain.
The team warns that damaging the nasal lining may increase the chances of bacteria making their way into the central nervous system.
Another interesting part of the study involves the sense of smell. Loss of smell is often one of the first signs of Alzheimer’s disease, sometimes appearing years before other symptoms.
Because of this, the researchers suggest that regular smell tests from around age 60 could help detect early signs of the disease. If a person starts to lose their sense of smell, it could be a clue that something is changing in the brain.
While the current study was done in mice, the team is already planning the next stage of research to confirm whether the same infection pathway exists in humans. If confirmed, it could lead to new ways of detecting, preventing, and possibly even treating Alzheimer’s disease by targeting infections that enter through the nose.
In the meantime, there are simple steps people can take to protect their nasal lining and reduce risk. Avoid picking your nose or plucking nose hairs, as both can harm the sensitive tissue inside the nose. Keeping this area healthy may help limit how many bacteria can reach the brain.
This research offers a fascinating look at the connection between our sense of smell, infections, and brain health. It opens the door to new ideas for early detection of Alzheimer’s and highlights the importance of taking care of even the smallest parts of our body—like the inside of our nose—for long-term brain health.
If you care about Alzheimer’s, please read studies about Vitamin D deficiency linked to Alzheimer’s, vascular dementia, and Oral cannabis extract may help reduce Alzheimer’s symptoms.
For more information about brain health, please see recent studies about Vitamin B9 deficiency linked to higher dementia risk, and results showing flavonoid-rich foods could improve survival in Parkinson’s disease.
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