Why Do You Get Sick in Winter? Science Finally Knows

Advertising Disclosure: When you buy something by clicking links on our site, we may earn a small commission, but it never affects the products or services we recommend.

Woman with a cold
aslysun / Shutterstock.com

Everybody knows that colds, flu and other similar illnesses spike during the winter months. Now, science has figured out why this happens.

An immune response unrecognized until a few years ago that takes place inside the nose and wards off bacteria may not work as well against viruses in colder temperatures, according to researchers at Harvard Medical School and Northeastern University.

Their findings were published recently in the Journal of Allergy and Clinical Immunology, a medical journal of the American Academy of Allergy, Asthma, and Immunology.

Many disease-causing pathogens enter the body through the nose. Cells near the front of the nose that detect the presence of such pathogens release billions of fluid-filled sacs — called extracellular vesicles — into the mucus of the nose. The vesicles then go on to attack the pathogens.

However, cold air might interfere with this immune response. Researchers took healthy volunteers from a room where the temperature was 74 degrees Fahrenheit to an environment where the temperature was about 40 degrees.

After about 15 minutes, the temperature inside the noses of volunteers fell by about 9 degrees. When this same lower temperature was applied to nasal tissue samples, it was found that the number of secreted extracellular vesicles dropped by almost 42% after the exposure to colder air.

In a summary of the study findings, Benjamin Bleier — Harvard Medical School associate professor of otolaryngology head and neck surgery at Mass Eye and Ear and senior author of the study — says:

“Conventionally, it was thought that cold and flu season occurred in cooler months because people are stuck indoors more where airborne viruses could spread more easily. Our study, however, points to a biological root cause for the seasonal variation in upper respiratory viral infections we see each year, most recently demonstrated throughout the COVID-19 pandemic.”

The researchers say this discovery might lead to better ways to strengthen the nose’s immune response during colder times of the year.

For example, a nasal spray could be used to boost the number of extracellular vesicles in the nose, or possibly to increase the number of binding receptors inside the vesicles.

For tips on staying healthy this winter, check out “3 Flu Shots Recommended for Seniors.”

Get smarter with your money!

Want the best money-news and tips to help you make more and spend less? Then sign up for the free Money Talks Newsletter to receive daily updates of personal finance news and advice, delivered straight to your inbox. Sign up for our free newsletter today.