Your mom was right — you can get sick by being outside in the cold. Chillier temperatures reduce the body’s ability to fight off viruses. That’s according to a new study published in the Journal of Allergy and Clinical Immunology.
Most viruses that cause the common cold (respiratory tract infection) are inhaled through the nose, where they bind to receptors, then replicate and spread throughout the body, explains Benjamin Bleier, MD, FACS, an associate professor at Harvard Medical School and one of the lead authors of the study.
“We breathe in about 10,000 liters of air a day. So you can imagine that we're constantly exposed to large volumes of these viruses and bacteria and other things in the environment. So our nose really has to work hard to protect our body from getting infected.”
He says that when the front of the nose detects pathogens, it triggers an alarm response. The nose is lined with cells that release “vesicles” into the nasal mucus. Vesicles attack the bacteria before they can infect the body.
In the study, Bleier found that a drop of 5 degrees Celsius (9 degrees Fahrenheit) meant a 50% reduction in vesicles. “What that meant is when we looked to see how much virus was growing in the cells, it was about double. … Just that … 15-minute exposure to cold air where you get a drop of about 5 degrees is enough to cut our immune defenses in half.”
The bottom line: We need to keep our noses warm.
Bleier says (COVID-driven) masks help here: “We assumed the masks were working because they were preventing us from actually inhaling the viruses. And I think they do a very good job of that. But also, it seems like maybe they're keeping this little blanket of warm air in front of our nose and at least limit that decline in temperature. So I think the masks may be doing more things than we ever thought, actually.”