There is a credible link between picking your nose and increasing the risk of developing dementia, according to a recent study. Picking your nose can sometimes damage international tissue, meaning bacteria have a clear path to the brain, which responds to the presence of bacteria in ways that resemble signs of Alzheimer's disease.

As many as 9 out of 10 people may pick their nose, with experts warning that picking your nose and plucking your nose hair is "not a good idea" because of the potential damage it does to protective nose tissue.

So far, the supporting evidence is based on mice rather than humans, but the findings could better our understanding of how Alzheimer's begins, which remains an enigma. Tests with a bacteria called Chlamydia pneumonia, which can infect humans, cause pneumonia, and has been found in most human brains affected by late on-set dementia, were run by a team of researchers led by scientists from Griffith University in Australia last year.

According to an article in ScienceAlert, the tests showed that the bacteria could travel up mice's olfactory nerve - joining the nasal cavity and the brain - and when there was damage to the nasal epithelium - the thin tissue along the roof of the nasal cavity - nerve infections got worse. This led to the mouse brains depositing more of the amyloid-beta protein.

This leads to a protein that is released in response to infections. Clumps of this protein are also found in hefty concentrations in people with Alzheimer's disease. Neuroscientist James St John from Griffith University said: "We're the first to show that Chlamydia pneumonia can go directly up the nose and into the brain where it can set off pathologies that look like Alzheimer's disease... the evidence is potentially scary for humans as well as mice."

The scientists were surprised by the speed at which C. pneumoniae took hold in the central nervous system of the mice, with infection happening within 24 to 72 hours. It is believed that bacteria and viruses see the nose as a quick route to the brain. St John continued: "We need to do this study in humans and confirm whether the same pathway operates in the same way. It's research that has been proposed by many people, but not yet completed. What we do know is that these same bacteria are present in humans, but we haven't worked out how they get there."