Researchers are investigating a "potentially scary" link between nose picking and Alzheimer's disease.

Dirty fingers introduce bacteria into the nose, resulting in infections that could lead to crusting, tissue damage and nosebleeds and now scientists are testing the theory that trauma to the nasal lining may transmit germs to the brain, possibly resulting in inflammation and amyloid plaques being formed, in line with the progressive neurodegenerative condition. Researchers have never been able to pinpoint the exact cause of Alezheimer's which gradually impairs various brain function such as memory, thinking, reasoning and judgment, and some have shifted their focus to the crucial nose-brain axis, the pathway between the nasal cavity and central nervous system.

The brain's smelling-processing centers are among the first areas damaged by Alzheimer's, so researchers have used smell tests as a non-invasive form of screening for the disease's risk. A 2022 study conducted by researchers at Griffith University in Australia found that nose picking can lead to Clamydia pneumoniae, which is bacteria causing respiratory tract infections into the olfactory nerve in the noses of mice that then travel to the brain, resulting in cells depositing amyloid beta protein. The fragments cling together to form sticky plaques, which disrupt cell communication and can result in brain cell death, memory loss and dementia.

“We’re the first to show that Chlamydia pneumoniae can go directly up the nose and into the brain, where it can set off pathologies that look like Alzheimer’s disease,” neuroscientist James St John said in the study, which was published in Scientific Reports. “We saw this happen in a mouse model, and the evidence is potentially scary for humans as well.”

An estimated 90% of the population is reported to pick their nose, with some doing so several times a day, according to data shared by the National Library of Medicine.