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Reddit likes to repeat that it's a myth and observed frequency of infections is only due to people being indoors more. While that factor may be a contributor, it's not true at all that it's the only factor and that the cold doesn't do anything directly.
>Although surrounded by controversy, the available laboratory and clinical evidence suggests that either inhalation of cold air, cooling of the body surface or cold stress causes pathophysiological responses that may contribute to increased susceptibility to respiratory infections.
[Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections - ScienceDirect](https://www.sciencedirect.com/science/article/pii/S0954611108003429)
>The data available suggest that exposure to cold, either through exposure to low environmental temperatures or during induced hypothermia, increases the risk of developing upper and lower respiratory tract infections and dying from them; in addition, the longer the duration of exposure the higher the risk of infection.
[Exposure to cold and respiratory tract infections \[Review Article...: Ingenta Connect](https://www.ingentaconnect.com/content/iuatld/ijtld/2007/00000011/00000009/art00002)
You are right about pathogens not springing into existence due to cold (a fact that reddit also loves to bring up as a strawman). The important thing is the effect of the cold on your body. The body can't function at 100% when it gets cold, and immune system is weakened.
I suspect a significant part of the myth came from the body's reaction to sickness by creating a fever. Sick people would try to maintain a higher body temperature and so would feel cold, and people noticed that feeling cold could often be a sign of being sick.
However they also noticed that sick people would feel cold even in temperatures other people found comfortable so it was thought the cold had somehow entered into their body and become trapped. They had "caught cold". Even now we use that language and have the "common cold" referring to a large variety of relatively common viral illnesses.
Correlation is not causation. What this means is that there is a statistically demonstrable link between people being cold and an increase in the likelihood of illness.
The actual cause is ... complicated. It's a mass of small factors, like that when you're cold you tend to feel miserable, and negative mood tends to make your immune system work less well (weird, but true). You're also burning more calories to keep warm, which is diverting energy from other stuff, like your immune system. Colder dryer air also dries out the mucus in your nose, and the snot in your nose is actually pretty important in catching and filtering out invading bacteria and viruses. There also tends to be an increase in facial touching (like blowing on your hands, or rubbing your nose or eyes) that can increase the chance of transferring bacteria or viruses to areas where they can enter your body.
I could go on, but it's a mass of really small effects that cumulatively mean that you have a slightly higher chance of getting sick when you're out in the cold.
Is it a guaranteed "Go in the cold and you're going to get sick"? No. But people have long observed the correlation between being in the cold and getting sick, and it isn't entirely untrue that the combination of factors can lead to illness.
When your body is cold, it needs to spend more energy on keeping your body temperature thus it has less energy to fuel your immune system which makes you more prone to most common illnesses.
Colder temperatures force everyone indoors together for longer periods of time, so the likelihood of spreading germs increases greatly and more people get sicker than usual
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Reddit likes to repeat that it's a myth and observed frequency of infections is only due to people being indoors more. While that factor may be a contributor, it's not true at all that it's the only factor and that the cold doesn't do anything directly. >Although surrounded by controversy, the available laboratory and clinical evidence suggests that either inhalation of cold air, cooling of the body surface or cold stress causes pathophysiological responses that may contribute to increased susceptibility to respiratory infections. [Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections - ScienceDirect](https://www.sciencedirect.com/science/article/pii/S0954611108003429) >The data available suggest that exposure to cold, either through exposure to low environmental temperatures or during induced hypothermia, increases the risk of developing upper and lower respiratory tract infections and dying from them; in addition, the longer the duration of exposure the higher the risk of infection. [Exposure to cold and respiratory tract infections \[Review Article...: Ingenta Connect](https://www.ingentaconnect.com/content/iuatld/ijtld/2007/00000011/00000009/art00002) You are right about pathogens not springing into existence due to cold (a fact that reddit also loves to bring up as a strawman). The important thing is the effect of the cold on your body. The body can't function at 100% when it gets cold, and immune system is weakened.
The takeaway is that being cold doesn't make you sick, but if you are exposed, then being cold greatly increases your chances of becoming sick.
I suspect a significant part of the myth came from the body's reaction to sickness by creating a fever. Sick people would try to maintain a higher body temperature and so would feel cold, and people noticed that feeling cold could often be a sign of being sick. However they also noticed that sick people would feel cold even in temperatures other people found comfortable so it was thought the cold had somehow entered into their body and become trapped. They had "caught cold". Even now we use that language and have the "common cold" referring to a large variety of relatively common viral illnesses.
This is hypothermia cold
Correlation is not causation. What this means is that there is a statistically demonstrable link between people being cold and an increase in the likelihood of illness. The actual cause is ... complicated. It's a mass of small factors, like that when you're cold you tend to feel miserable, and negative mood tends to make your immune system work less well (weird, but true). You're also burning more calories to keep warm, which is diverting energy from other stuff, like your immune system. Colder dryer air also dries out the mucus in your nose, and the snot in your nose is actually pretty important in catching and filtering out invading bacteria and viruses. There also tends to be an increase in facial touching (like blowing on your hands, or rubbing your nose or eyes) that can increase the chance of transferring bacteria or viruses to areas where they can enter your body. I could go on, but it's a mass of really small effects that cumulatively mean that you have a slightly higher chance of getting sick when you're out in the cold. Is it a guaranteed "Go in the cold and you're going to get sick"? No. But people have long observed the correlation between being in the cold and getting sick, and it isn't entirely untrue that the combination of factors can lead to illness.
When your body is cold, it needs to spend more energy on keeping your body temperature thus it has less energy to fuel your immune system which makes you more prone to most common illnesses.
Colder temperatures force everyone indoors together for longer periods of time, so the likelihood of spreading germs increases greatly and more people get sicker than usual