Cold weather doesn’t make kids sick — viruses do.

We grew up hearing the same warning: “Put your hat on, or you’ll catch a cold.” Even today, I still hear it as winter approaches. But physiologically, cold air does not create illness. Viruses do.

Respiratory symptoms — runny nose, congestion, cough, and fever — occur only after a pathogen has already entered the body and triggered an immune response. Feeling cold or uncomfortable is not an illness. It simply means the body is thermoregulating — working to maintain core body temperature, which is a normal and healthy process.

 

Why We See More Illness in Winter:

We often blame the temperature, but the real drivers of winter illness are environmental and behavioral changes that occur when it gets cold.

 

What Actually Drives Viral Spread:

-Increased indoor crowding (schools, daycares, indoor play spaces, stores, family gatherings)

-Reduced ventilation (windows closed, shared air for long periods)

-Dry heated indoor air that causes the mucosal lining of the nose and throat to lose moisture, making it easier for viruses to enter

-Less sunlight, which may reduce vitamin D production — and vitamin D plays a regulatory role in immune function

-More face-to-face respiratory exchange (talking closely, sharing utensils, coughing in small spaces)

This combination — reduced airflow, shared air, and dry airways — is what increases viral exposure and transmission. Not cold, fresh outdoor air.

 

“But Doesn’t Cold Weather Weaken the Immune System?”

This is the question I hear the most. And it makes sense why: when someone is shivering or tense, it appears their body is under strain. But physiologically, feeling cold is not the same as immunosuppression.

When exposed to cold air — especially when underdressed — the body activates a thermoregulatory response:

-Blood flow is redirected toward vital organs

-Blood flow to the skin and extremities decreases (peripheral vasoconstriction)

-Muscles may contract to generate heat (shivering)

-Movement may slow to conserve energy

This process is protective—not harmful. It does not generate illness. It simply conserves heat.

 

What actually weakens immune function long-term is:

-chronic stress

-persistent inflammatory load

-inadequate sleep

-dehydration

-nutritional deficiency

-lack of movement

-high viral exposure indoors

Those are biological stressors. A winter breeze is not.

 

Case Study 1 — Jørgensen et al. (2020–2022): Real-World Preschool Observation in Northern Europe

Jørgensen and colleagues followed two preschool groups over the winter season from 2020 to 2022:

-One group spent most of their time indoors

-The other group spent structured time outdoors daily, including during cold weather

-Both groups had similar ages, vaccination status, and socioeconomic backgrounds

-Researchers tracked respiratory symptoms and absentee rates throughout the season.

The key finding was that the outdoor group had fewer respiratory sick days overall. Illness still occurred — but it did not spread as widely. The difference was not the temperature; it was the ventilation.

Children outdoors consistently breathed fresh, moving air.

Children indoors inhaled recirculated air, where viruses remained suspended and transmissible for longer periods.

 

Case Study 2 — Foxman et al. (2015, Yale University): Laboratory Study on Airway Cells at Low Temperatures

A 2015 study by Foxman et al. is often misinterpreted as evidence that cold air weakens immunity. The researchers examined isolated mouse airway epithelial cells kept at lower temperatures in a laboratory setting. These cells showed a slightly slower response to viral particles when compared to cells at warmer temperatures.

However, the researchers explicitly cautioned that these conditions do not reflect real-world human physiology, especially when people are clothed, moving, breathing fresh air, and supported by normal hormonal and metabolic regulation.

Furthermore, observational studies of outdoor “forest school” children in Nordic countries found no increase in illness among those spending several hours outside daily — even near freezing temperatures — as long as clothing and movement were adequate. Again, the cold itself was not the problem. The level of viral exposure was.

 

What Proper Clothing Actually Does:

-Clothing does not block viruses. What it does is allow the body to regulate naturally:

-Maintains stable core temperature

-Preserves circulation and movement

-Allows healthy lung expansion and deep breathing

-Supports metabolic efficiency and muscle activity

-Reduces discomfort that might limit physical activity

A hat helps retain heat. Gloves allow continued exploration. A scarf protects sensitive skin and helps moderate the temperature of inhaled air. These support comfort, mobility, and regulation — not viral defense.

Read our blog on:  how to dress for winter 

Reminder:

This article is not medical advice. Always consult your pediatrician or primary care provider — especially if your child has:

-asthma or reactive airways

-autoimmune or inflammatory conditions

-cardiac issues

-chronic illness

-history of respiratory complications

Cold air and poor air quality are not the same thing. If pollution levels or smoke advisories are high, medical guidance should be followed. Children who are sick, febrile, or fatigued should rest indoors and recover.

Nature supports immune health — but it does not replace medicine.