A study published in 2022 revealed a tenuous but plausible link between picking your nose and increasing the risk of developing dementia.

In cases where picking at your nose damages internal tissues, critical species of bacteria have a clearer path to the brain, which responds to their presence in ways that resemble signs of Alzheimer's disease.

https://www.sciencealert.com/mouse-study-suggests-surprising-link-between-alzheimers-and-nose-picking