- New research has found that cold temperatures lower immunity in the nose and make us more susceptible to viruses.
- A drop in nasal tissue temperature of just 5° C reduced immune response by almost half.
- The findings help explain why we’re more prone to catching colds and flu during winter.
- Vitamin C and hand washing measures can help protect us from common colds.
The average American adult experiences
For years, it’s been thought that cold and flu viruses are rife during winter because chillier temperatures drive everyone indoors. And, being in close proximity to a group allows viruses to transfer from one person to another more easily.
But now new research published this month from a team at Massachusetts Eye and Ear hospital and Northeastern University suggests there may be biological reasons that we are at significantly increased risk of getting sick when temperatures drop.
Virus particles enter the nose in two ways: through inhalation or direct touch.
“The nose is one of the first points of contact between the outside world and inside the body,” stated Dr Benjamin Bleier, director of Otolaryngology Translational Research at Mass. Eye and Ear, and a co-author of the study published in The Journal of Allergy and Clinical Immunology.
After virus particles make their way in, the cells in our nasal cavities swiftly activate to start expelling them. However, the new study findings indicate that colder temperatures significantly impair this immune response.
Let’s go back a few steps to better understand what happens when a virus enters the nasal cavity.
In 2018, Bleier and a team of scientists from Mass. Eye and Ear and Northeastern University found that when nasal cells at the front of the nose detect bacteria, it prompts the release of billions of tiny sacs filled with fluid.
Known as ‘extracellular vesicles’ (EVs), these sacs quickly move into the mucus to “surround and attack the bacteria before they have a chance to infect the cells,” Bleier explained to Healthline.
Basically these EVs attempt to kill the bacteria before they can start to cause a major infection in the body.
From here, the researchers were encouraged to investigate further to see what happens when viruses enter the nose.
Bleier explained: “This led our team to look at whether this same response happened for some of the viruses that cause common upper respiratory infections, like the common cold.”
They learned that, in the case of three common cold viruses, the EVs are released and respond in the same way: surrounding and attacking the virus particles in the mucus.
“These vesicles contained molecules (called microRNA), which then killed the viruses,” Bleier explained. This means the EVs were “effectively mopping up the viruses before they could bind to the nasal cells and initiate an infection.”
In addition, the EVs also acted as ‘decoys’ — causing the virus particles to attach to the EVs rather than nasal cells.
But the investigations didn’t end there. Bleier and his team hypothesized that because colds and flu are more common in winter, this nasal immune response may be impacted by cold air.
So, they exposed nasal tissues to temperatures of 39.9° F or 4.4° C — and found that doing so led to about 9° F or 5° C decrease in tissue temperature, with major consequences for the immune system.
“This drop significantly reduced this innate immune response in the nose,” Bleier explained.
The number of EVs that were released decreased by over 40%, while their quality was also severely compromised.
“This reduced response can make the virus more able to both stick to and infect the nasal cells,” revealed Bleier. From there, “they can divide and cause infection.”
Bleier and his team believe the recent findings are significant.
“To our knowledge, this study is the first to offer a biological explanation for why people are more likely to develop upper respiratory infections like cold, flu, and COVID-19 in colder temperatures,” he stated.
Unlike some other viruses, cold-related symptoms typically occur in one area: the nose.
The most predominant signs of a cold, shared Dr. Edward Kuan, a specialist in otolaryngology-head and neck surgery, rhinology, at UCI Health in California, are:
- Stuffy and runny nose
- Postnasal drip
The latter, he told Healthline, may also lead to a sore throat and cough. Furthermore, he added, some patients “can have more systemic symptoms, such as mild fever or fatigue.”
While nobody is immune to cold or flu germs, there are some individuals whose bodies are less able to defend against them. As such, they may experience more severe symptoms or complications.
Kuan revealed that these groups include:
- Young children, as their immune systems are still developing
- People who live or work in highly populated or dense settings
- Individuals with decreased immune system function
- Cancer patients
- Those who have undergone transplants
Dr. Abeer Siddiqi, a board-certified allergist and clinical immunologist at Houston ENT and Allergy, told Healthline that getting enough vitamin C may help bolster our nasal defenses.
She stated that this nutrient has been shown to enhance our mucus membranes (the primary nasal tissue) as well as overall immunity.
Vitamin C acts as a powerful micronutrient, antioxidant, and cofactor (or ‘helper’) for our body’s enzymes, she revealed. And these enzymes are crucial as they “assist in optimal functioning of [our] innate immune cells, including white blood cells.”
Siddiqi continued that, in general, “vitamin C will help support immunity in every part of the body that has a dense network of immune cells and tissues.”
The nutrient is readily available in various foods such as oranges, broccoli, and red peppers.
Aside from vitamin C, Siddiqi said basic hygiene measures can also protect you from getting sick. These include:
- Hand washing
- Hand sanitizing
- Wearing a high-quality face mask (especially in crowded spaces)
- Covering your mouth while sneezing or coughing
- Isolating when sick
The new research is crucial in better understanding how our bodies react to viruses in different environments — and exploring potential treatments.
“We hope our findings can lead to therapeutic approaches to bolster the innate immune response inside the nose or increase the number of extracellular vesicles, such as through a nasal spray,” stated Bleier.
In the meantime, measures such as taking vitamin C or wearing a mask in crowded spaces can help defend your nose — and keep it warm on chillier days.