Obviously, diseases like the cold and flu are cause by viruses, so weather alone wouldn’t cause it. So why do we get runny nose, sneezing, and other symptoms when we go out in the cold without a jacket?
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moving from extreme temperatures (hot to freezing or vice versa) is jarring to the nerves. Runny nose occurs because of dry air. Vasodilation may also cause these
Imagine your nose and sinuses are a little water balloon you carry around with you. If you put a water balloon in the freezer for 45 minutes, then take it out to let it come to room temp a lot of things would happen. You would notice that the water in the balloon begins to turn to slush (stuffy nose), or that the balloon might spring a leak (drippy nose). Your body and your sinuses are very dynamic environments that are highly affected by temperature and humidity changes.
Your body needs to stay a consistent temperature to prevent you from dying. Too high and you cook, too low and your chemistry can’t happen anymore. All the parts of you that are exposed to the temperature outside act as buffers, to prevent the temperature at your core from changing too much.
Your nose’s main job is to warm up and humidify the air as if enters your body, to prevent your lungs from getting too cold or drying out. The main way it does that is by increasing the blood flow to capillaries, which allows for heat to be transferred from your bloodstream to the air entering your body. That also causes water to filter out though, which makes for a runny nose. As your nose gets runny, the snot triggers the sensitive hairs in your nose, which cause a sneeze thinking that something is entering your body.
As for other symptoms, it has to do with how your body senses temperature. You have a sensor in your brain that tells it if you’re too cold or too hot. If you’re too cold, your brain amps up your metabolism, and forces your muscles to contract rapidly to turn glucose into heat. That’s called shivering. When you have an infection, your immune system highjacks the sensor, turning up the thermostat, in an attempt to kill the germs, which makes your brain think you’re too cold, and triggers the same shivering.
I once had a pulmonologist say that there are pathogens suspended in your mucus. When cold air dries the mucus out the pathogens come in direct contact with your tissues and enter your blood stream. I’ve not seen literature on this, though
Cold air can lower your immune system. A virus you were exposed to but would have fought off and not noticed in warm weather, can make you sick in the cold when your immune system is less active. Lack of sunlight in the winter months in general can also lower your immune system response.
You won’t find this in literature, but humour me. You have only so much energy in the body. A lot of that goes to cell restoration, metabolism, heating the body etc. Part of that goes to immune defence. When you expose yourself to the cold, more of your available energy needs to be spent on heating yourself, so less is available for immune response. Therefore your immune system is somewhat less effective.
“The lowering of your body temperature creates the conditions needed for a virus or bacteria to battle your immune system”
> Obviously, diseases like the cold and flu are cause by viruses, so weather alone wouldn’t cause it. So why do we get runny nose, sneezing, and other symptoms when we go out in the cold without a jacket?
Ok, I think there are 2 different things here:
1. Many viruses survive better in cold, dry air. So they spread better in winter .
2. Cold air irritated the sensitive membranes in your nose, causing your nose to run even if you’re not sick.
3. Cold reduces the blood flow to those same membranes, lowering immune response.
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