Does cold weather make you ill?

As temperatures drop in the UK's first real cold snap of winter, people are bracing for a wave of colds and coughs. "The cold weather will most probably push up colds and other respiratory viruses this week," virologist Professor Steve Griffin of Leeds University told the i news site.

Does cold weather actually make us ill?

No, cold weather doesn't directly cause illness. But it certainly creates conditions for viruses to thrive. Chillier weather drives more people indoors, giving viruses a better chance to spread in close quarters. Plus, when temperatures drop, we are more likely to keep our windows closed, reducing ventilation and further encouraging the spread of seasonal sniffles.

So cold temperatures have nothing to do with it?

It turns out there's a bit more to it than that. Colder temperatures do weaken our immune response, according to a ground-breaking 2022 study published in The Journal of Allergy and Clinical Immunology. The study examined an immune response in the nose that causes the cells lining the nasal cavity to release loads of virus-fighting particles, called extracellular vesicles (EVs). The researchers found that, when cold weather causes temperatures inside the nose to drop – from 37 degrees Celsius to 32 degrees Celsius, in their study – the release of EVs slows, and so does their antiviral response.

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"We found this drop significantly reduced this innate immune response in the nose, decreasing not only the quantity of extracellular vesicles that swarmed the virus but the quality of them," study lead Professor Benjamin Bleier from Harvard Medical School told Medical News Today. "This reduced response can make the virus more able both to stick to and infect the nasal cells, where they can then divide and cause the infection."

What else could be making us feel under the weather? 

Keeping our windows and doors shut to keep the warmth in and heating costs down probably isn't making us feel great, either. Doing all this can worsen indoor air quality, John Durant, a Tufts University professor who studies indoor air quality, told The Guardian. When heating systems are turned on, they can release allergens, dust and mould into the air, adding to pollutants already present, such as cleaning-product chemicals and cooking fumes. Without regular fresh air, these particles can cause irritation.

On top of that, warm indoor air tends to dehydrate us. "I think it’s fair to say that you’re kind of bombarding yourself with a mixture of environmental insults simultaneously when you heat your air, close your windows, dehydrate yourself and expose yourself to what’s present in your air ducts," said Durant.

How can we stay healthy during the winter?

To lower your chances of catching a cold or flu, wash your hands frequently with soap and water, especially after touching surfaces or shared items. Hand sanitiser is also effective. And, as bacteria and viruses often enter through the mouth, eyes, and nose, avoid touching your face as much as possible.

"Aside from practising good hygiene, the maintenance of a strong immune system is crucial for long-term protection," GP Dr Donald Grant told The Mirror. To help boost the immune system, "aim to get around seven to nine hours of sleep each night, eat well-balanced, nutritional meals and manage water intake."