system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we get sick when its' cold? Does it have to do with the temperature or some other factors?
gpt
This question always gets answered with the received wisdom that goes something like. 'It's not because of the cold, it's because we spend more time in the warm indoors with other people....' well that's not actually true, it IS because of the cold AS WELL. 

When we're cold, our bodies restrict blood flow to our extremities, including our nose, to protect the vital organs. Less blood flow means less white blood cells reaching the nasal passages so infections which start there are less likely to be fought off in the early stages and so they're more likely to get bad enough for us to notice them.