Ask Glenn

Why do you feel hot when you have a cold?

Because your body turns up the heat on purpose to help fight off the nasties. After all, it’s a virus – not cold weather – that causes the cold in the first place.

Don’t you catch a cold because you ‘catch a chill’?

Not really. If you think about it, plenty of people complain of ‘summer colds’, and you can get cold all the time in the winter without necessarily coming down with a cold.

Boy with temperature

But you do get them more often in winter, so how do you explain that?

‘Catching a cold’ results from a combination of dropping your body temperature and inhaling or swallowing droplets of water containing certain types of virus. The main ones that cause colds are called adenoviruses and rhinoviruses. In winter, the cold weather can cause your core body temperature to drop if you don’t wrap up in warm clothes. This makes you less able to fight off infection, but you still have to get the viruses from somewhere in the first place.

So where do they come from?

Well, the other thing that happens in cold weather is that people cluster together indoors more often than they do in summer. This gives more chances for the viruses to spread as you breathe in virus-laden water droplets that are sneezed, coughed, or simply breathed out by other people. Once these droplets are breathed in, the nasties settle in the lining of your nose, throat, or lungs and start to multiply. Your immune system can usually fight them off after a day or two, and all you get is a bit tired and snotty. But some nastier viruses (especially the ones that make it to your lungs) can last for weeks, and make you very ill.

So how does getting hotter help?

Getting hotter, or developing a fever, is one of your body’s natural responses to infection. This is because the kind of bacteria and viruses that infect us have evolved over millions of years to work best at the normal human body temperature of 37°C. This is because the proteins they use to make copies of themselves only work at this temperature. Raise the temperature by just one or two degrees, and these proteins unfold and break apart, and the bacteria or virus stops multiplying and dies.

So fevers are healthy?

Well, usually they’re a sign of infection by viruses or bacteria, but also that the body is trying to fight them off. So generally speaking you should let them do their thing, rather than try and cool off with ice packs or wet towels. Problems only come if they go on too long, or your body temperature gets so high that your body’s own proteins stop working, too. This happens at body temperatures of 40°C or over, but this hardly ever occurs with colds, only with nastier diseases like pneumonia.

So if colds make you hot, why call them ‘colds’?

That probably started when people associated them with cold weather. Plus you can’t tell someone you have the ‘hots’, or they might think you fancy them!

What about ‘the snots’?

Well, that certainly is more descriptive...