Here’s another good reason for keeping your hands clean and your fingers out of your nose: Alzheimer’s disease. A recent review published in the journal Biomolecules claims the habit of nose-picking could introduce pathogens into the brain that may trigger neuroinflammation that can lead to Alzheimer’s disease. The authors of the study suggest that viral, bacterial, and fungal pathogens enter the brain through the nose and olfactory system.

Picking your nose may introduce these pathogens to the olfactory system by contamination of hands with soil and feces, said the researchers, and this can cause inflammation in the brain. According to USA TODAY, beta-amyloid, a protein believed to be a factor in causing Alzheimer’s disease, may be produced by the brain in response to these pathogens.

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Heather M. Snyder, vice president of medical and scientific relations at the Alzheimer’s Association, said that the report reflected previous studies, but added that the scientists suggested, but did not prove, that the pathogens can enter the brain through the nose and could be linked to the development of dementia or Alzheimer’s.

“Alzheimer’s is a complex disease with many contributing factors,” she said. “There are likely multiple causes that contribute to the underlying biology of the disease. Increasingly, we know that the immune system plays an important role in the underling biology of Alzheimer’s.”

The researchers from Western Sydney University in Australia say that that the olfactory system in the roof of the nasal cavity has a direct path to the areas of the brain in which Alzheimer’s wreaks havoc. They point out that in recent years, research has suggested that neuroinflammation may play a partial role in the development of the disease. They say that nose-picking could indirectly lead to brain inflammation by pushing pathogens into the brain or pulling stuff out of our nose that affects the microbiome balance of the brain, says ScienceAlert.

In 2022, another study linked nose-picking with Alzheimer’s although this one focused on mice. It showed that damage to the tissue lining the nasal cavity could increase the risk of infection, leading to a response in the brain like that is seen in Alzheimer’s patients. The latest research reveals that some viruses are found regularly in the brains of people suffering from Alzheimer’s disease, and that the first signs of the disease are often spotted in the olfactory bulb, the part of the brain that detects smells.

While scientists are still a long way from a definitive conclusion that picking your nose increases the risk of Alzheimer’s, the indications are there, and may illuminate effective treatment. The researchers noted that understanding the potential role of olfactory pathogen entry may open the doors for new avenues of prevention as well.

“Among the entry routes, the improvement of hand hygiene might be an easy prevention step, as learned from the COVID-19 epidemic,” they wrote.