Scientists may have uncovered exactly why we are more prone to falling ill when the temperature drops – and it’s all to do with your nose.
Up until now, it was widely believed that illnesses become more common in the colder temperatures because people spend more time indoors, breathing in built-up air which can’t circulate properly.
But a new study now suggests a previously unidentified immune response inside your nose fights off viruses which cause respiratory infections – only it can’t operate fully when it’s cold.
That’s because the nose, mouth and throat are the main ways for viruses to get into the body, which are usually either inhaled or spread via the hands.
Researchers from Boston’s Mass Eye and Ear hospital and the Northeastern University have subsequently concluded there is a “biological root cause for the seasonal variation” in these viral infections seen every year – particularly throughout the Covid pandemic.
It all began in 2018, when a study from Northeastern University found that the nose reacts when bacteria is inhaled.
The cells at the front detect the bacteria, then release billions of tiny fluid-filled sacs into the mucus to attack the imposters.
Antibacterial proteins then move to the back of the airway to protect other cells against the intruder.
The new study, published in The Journal of Allergy and Clinical Immunology, built on these findings by testing the same mechanisms but with viruses.
The scientists were particularly interested in the most common upper respiratory infections – Covid, and the two rhinoviruses which cause the common cold.
They found that the nose did respond slightly differently to the virus, but they were still effective in fighting it off – until they were exposed to cold.
Healthy people were exposed to 4.4ºC for 15 minutes, meaning the temperature in the nose fell to around 5ºC.
The number of virus fighting sac released dropped by nearly 42% in the cold.
The researchers are hoping they find similar outcomes with other diseases in the future.
These findings could also help reduce our susceptibility to the common cold, as scientists are looking into how to strengthen the nose’s immune response, for instance, through a nasal spray which increases fluid-filled sacs.
