People who frequently pick their noses may be at a higher risk of developing Alzheimer's disease, according to a review of dozens of published studies.

While scientists cannot accurately pinpoint what causes Alzheimer’s disease, in the brains of patients, they have observed a buildup of a protein called tau, which is associated with the body’s immune response.

But recent studies have pointed to the role of neuroinflammation, at least partially in its pathogenesis.

In the new study, researchers at the Western Sydney University in Australia "hypothesised that neuroinflammation in Alzheimer’s may be partially caused by viral, bacterial and fungal pathogens entering the brain via the nose and the olfactory system."

Chronic nose-picking, medically known as rhinotillexomania, introduces germs into the sensitive nasal cavity that cause inflammation in the brain, which has been linked to the onset of Alzheimer’s disease.

In the paper, published in the journal Biomolecules, the team supported this theory, suggesting that shifts in the nasal environment caused by an overgrowth of germs could be the source of chronic, mild brain infections.

The researchers said that such infections can exist seemingly without symptoms. Still, they may cause inflammation and leave behind harmful plaques of protein that contribute to the development of neurodegenerative diseases, including Alzheimer’s.

"One of the lessons learned from COVID is the value of hand hygiene through frequent hand washing and the use of hand sanitisers, and we suggest these routine hygienic procedures be mandatory procedures for the incurable nose-picker," the researchers wrote in the paper.