Why your cheeks go rosy in the cold and what else happens to your body when it's freezing outside; Ever wondered why your cheeks go red?
We all shiver in the cold, but what actually happens to our bodies when thetemperature drops below freezing?
Most people probably know that our core body temperature is 37 degrees Celsius. Any changes to this temperature, either above or below, could signal medical concerns and in some cases, a threat to life.
Our body temperature is regulated by a part of the brain called the hypothalamus, which acts like a kind of human thermostat.
There are several measures the body can take to try to combat cold, some more extreme and serious than others.
Here's what they are and why they happen.
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Cheeks flushing or vasoconstriction take place when your blood vessels narrow to reduce blood flow near the body's surface. Sometimes the blood vessels dilate and burst, which causes redness.
This can also numb your hands.
Cold and dry air can cause difficulty for your lungs. Your nose wants to moisturise, but it can overcompensate and cause it to run.
Shivering caused by cold or oscillatory muscular activity, to use the medical term, usually occurs when your core body temperature has dropped about a degree below its normal temperature.
As a result your muscles contract and expand in speedy bursts, while your jaw muscles might begin to cause your teeth to chatter, in a bid to produce heat, which helps to raise body temperature.
Moving to the more serious effects of cold, shivering can also be a sign of hypothermia.
Other symptoms include cold and pale skin, slurred speech, fast breathing, tiredness and confusion.
Hypothermia sets in when the body temperature falls below 35 degrees Celsius.
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Frostbite, brought on in freezing temperatures, can affect any part of your body, but the extremities, such as the hands, feet, ears, nose and lips, are most likely to be affected.
It is a direct reaction to the cold as the body responds by narrowing the blood vessels and slows down blood flow to the extremities so flow to the vital organs can be increased.
Although colds and flu are caused by viruses, not cold weather, there are more of them about in winter and there is evidence that our immune systems don't work so well if we are cold, making us more susceptible to these infections which can be very serious indeed.
Cold weather changes how the body controls the flow of blood around it and causes a number of other changes. It has been known for some years that cold weather can cause our blood pressure to rise. In people at risk, this can bring on a stroke or heart attack: both of which are seen more often in winter.
Pneumonia (severe lung infection) is seen more commonly in cold weather in patients at risk. Again this may be due to changes in the body's ability to fight off infections.
Professor Hamish Laing, executive medical director and CIO of ABM University Health Board, said some people were obviously more susceptible to cold weather than others.
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He said: "The elderly, pregnant, people with chronic conditions and the very young are most at risk in cold weather."
Falls are also more common in the elderly when it is cold. This may be due to changes in their blood pressure. Of course, if it is icy, then that is another reason
Finally, there is some evidence that cold weather can affect adversely people who already have depression and dementia. The way this happens is not well understood.
The critical message is that people who are vulnerable to cold should try and stay warm even if that does mean having the heating on more over the coming days. Keeping active is also important, moving around inside the home rather than sitting down all the time.
Warm food and drinks can also help and wearing lots of thin layers helps to trap the heat better than one thick woolly jumper. Lots of heat is lost through the scalp, especially if you have little hair, and so wearing a hat can help reduce heat-loss.
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