Theory Links Alzheimer's to Nose Infections
A mathematician who lost her father to Alzheimer's has shared a theory that the disease could begin in the nose.
Updated on Nov. 3, 2026 in Alzheimer’s
Professor Hannah Fry shared a theory that Alzheimer's could start in the nose, citing research in which chlamydia pneumonia placed in mouse noses reached the brain within 72 hours. The theory was discussed in her New Scientist column and an Instagram video.
Why it matters
The olfactory nerves pass through tiny holes in the skull behind the eyes and nose, offering a possible route for infections to reach the brain. Alzheimer's is the most common cause of dementia in the UK, according to the NHS, so a clearer understanding of how the disease starts could shape future research.
The theory draws on a mouse study in which chlamydia pneumonia placed in the nose reached the brain within 72 hours, producing plaques and inflammation resembling Alzheimer's. Whether the same process occurs in people has not been established by the findings reported so far.
The players
Hannah Fry
Hannah Fry is a British mathematician and broadcaster who appeared on Celebrity Traitors and shared the theory in her New Scientist column.
The details
Fry described research in which researchers squirted chlamydia pneumonia up the noses of mice and tracked its spread. In a separate study, metal fragments were found in the brains of stray dogs living in heavily polluted Mexican cities, each surrounded by plaques and inflammation. A study of young children and adults in polluted areas reportedly found the same pattern.
Timeline
2025: Fry's father died of Alzheimer's.
November 3, 2026: Article published on the nose-Alzheimer's theory.
Health Landscape
The theory extends research on the olfactory nerves, which pass through small openings in the skull behind the eyes and nose and offer a direct route from the nasal cavity to the brain. It proposes that airborne infections and pollution particles could follow that route toward the neurodegeneration seen in Alzheimer's.
For people concerned about memory changes, the theory does not yet change recommended care or screening. Anyone with questions about Alzheimer's symptoms or support should speak with a doctor or specialist.
The takeaway
The theory is a hypothesis drawn from animal and observational studies, not an established cause of Alzheimer's. Readers should treat it as an open research question while the disease's origins remain under study.
Further reading
Explore more on Alzheimer's for background on how the disease is studied and treated.
More information
Find support and information from the Alzheimer's Society.
