Many people pick their nose out of habit, boredom, or irritation. While the behavior is commonly discouraged for hygiene reasons, media reports in recent years have suggested that nose picking may increase the risk of Alzheimer’s disease or dementia.
These claims originate from scientific studies conducted in mouse models, not humans. A careful review of the research shows that while the findings raise biologically plausible questions, they do not establish that nose picking causes Alzheimer’s disease in people.
Recent health news outlets have revisited the 2022 mouse study because of ongoing interest in how everyday behaviors might affect long-term brain health. Multiple media reports in late 2025 highlighted the original findings and discussed the possible biological mechanisms in mice that could connect nasal exposure to Chlamydia pneumoniae with Alzheimer’s-like changes in the brain. However, scientists continue to emphasize that the study’s results are based on a mouse model and do not demonstrate causation in humans.
The most widely cited research was published in Scientific Reports in 2022. The study investigated whether a respiratory bacterium could access the brain through the nasal route. [1]
The study was conducted entirely in mice.
Researchers focused on Chlamydia pneumoniae, a bacterium known to cause respiratory infections in humans.
The bacterium was introduced into the nasal cavity of mice under laboratory conditions.
Some mice had mild damage to the nasal lining, simulating reduced barrier protection.
Researchers tracked whether the bacteria could travel from the nose into the brain.
Chlamydia pneumoniae was able to move from the nasal cavity to the brain via the olfactory nerve pathway.
Once in the brain, infected mice showed increased production of amyloid beta protein.
Amyloid beta is the protein associated with plaque formation in Alzheimer’s disease.
The researchers observed that amyloid beta accumulation occurred rapidly, within days of infection. This timeline is very different from Alzheimer’s disease in humans, which develops over many years.
The olfactory nerve is responsible for the sense of smell and has a unique anatomical feature.
Olfactory nerve endings are located in the upper nasal cavity.
These nerve fibers pass through the cribriform plate, a thin bone at the base of the skull.
This creates a direct connection between the nasal cavity and the brain.
In experimental models, this pathway can allow certain pathogens to bypass the blood brain barrier. However, the presence of this pathway does not mean that everyday nasal contact or behaviors routinely lead to brain infection in humans.
The 2022 study did not directly examine nose picking as a behavior.
The connection arose because:
Nose picking can cause small injuries to the nasal lining.
Damaged nasal tissue may reduce local defense mechanisms.
The mouse study showed that bacteria entered the brain more easily when the nasal lining was compromised.
This led to media headlines linking nose picking to Alzheimer’s disease. The study itself did not measure behavioral habits, frequency of nose picking, or long term cognitive outcomes.
The 2022 findings are consistent with earlier research but also differ in important ways.
In 2008, a study suggested that C. pneumoniae infection may cause late-onset Alzheimer’s disease. [3]
A similar study in 2010 linked C. pneumoniae infection to Alzheimer’s pathogenesis, revealing a correlation between C. pneumoniae with amyloid deposits, and neurofibrillary tangles together in the brain. [4]
These studies suggested an association, not a cause and effect relationship.
Results were inconsistent across research groups.
Focus on infection related mechanisms in Alzheimer’s disease
Interest in amyloid beta as a biological response
Exploration of inflammation and immune activation in the brain
Earlier studies examined human brain tissue, often postmortem.
The 2022 study used live mice, allowing direct observation of bacterial movement.
The rapid amyloid response in mice does not match the slow progression of Alzheimer’s disease in humans.
At present, there is no direct evidence that nose picking increases the risk of Alzheimer’s disease or dementia in humans.
The findings discussed come from controlled experiments in mice, where bacteria were deliberately introduced into the nasal cavity. Human exposure patterns, immune responses, and disease development differ significantly.
Researchers have not shown that Chlamydia pneumoniae or similar microbes routinely enter the human brain through the olfactory nerve during normal activities such as nose picking. Long term human studies linking nasal injury to Alzheimer’s disease are lacking.
Alzheimer’s disease is a multifactorial condition, influenced by age, genetics, vascular health, metabolic disorders, and lifestyle factors. No single habit has been proven to independently cause the disease.
The current evidence remains hypothesis generating, not causal.
While nose picking has not been proven to cause Alzheimer’s disease, medical professionals discourage the habit for established health reasons.
Frequent nose picking can:
Damage the delicate lining of the nasal cavity
Increase the risk of nosebleeds
Introduce bacteria and viruses from the hands into the nose
Spread germs to nearby surfaces and other people
Worsen nasal irritation and inflammation
The nose serves as a natural filter for airborne particles. Repeated injury to its lining can weaken this protective function.
If nasal discomfort or blockage leads to nose picking, safer options are available.
These include:
Using saline nasal sprays or drops to keep nasal passages moist
Gently blowing the nose with clean tissue
Using a clean cotton swab only at the outer edge of the nostrils
Drinking adequate fluids to reduce nasal dryness
Managing allergies or chronic congestion with medical advice
Persistent nasal bleeding, pain, or crusting should be evaluated by an ear, nose, and throat specialist.
Loss of smell is recognized as an early symptom in Alzheimer’s disease and other neurodegenerative conditions.
Smell testing is sometimes used in research to identify early brain changes.
Smell loss reflects involvement of brain pathways rather than nasal infection alone.
This does not mean that nasal injury causes dementia but highlights the close relationship between the olfactory system and brain health.
The studies were conducted in mouse models, not humans.
The olfactory nerve pathway is biologically plausible but not proven as a disease route in everyday human behavior.
The findings do not show that nose picking causes Alzheimer’s disease.
Media headlines may overstate risk by implying causation where none has been established.
Carey, R. M., et al. “Chlamydia pneumoniae infection induces Alzheimer’s disease like pathology in mouse brain.” Scientific Reports. 2022.
https://www.nature.com/articles/s41598-022-06749-9
McRae, M. “Mouse study suggests nose picking has a surprising link with Alzheimer’s.” ScienceAlert. 2022.
https://www.sciencealert.com/mouse-study-suggests-nose-picking-has-a-surprising-link-with-alzheimers
Balin, Brian J., Christine J. Hammond, Christopher S. Little, Susan T. Hingley, Denah M. Appelt, Judith A. Whittum-Hudson, and Alan P. Hudson. “Immunohistological Detection of Chlamydia pneumoniae in the Alzheimer’s Disease Brain.” BMC Neuroscience 11 (2010): 121. https://doi.org/10.1186/1471-2202-11-121. Accessed December 15, 2025.
Balin, B. J. “Chlamydophila Pneumoniae and the Etiology of Late-Onset Alzheimer’s Disease.” Journal of Alzheimer’s Disease 13 (2008): article details. https://doi.org/10.3233/JAD-2008-13403. Accessed December 15, 2025.
