Why do I have cold feet but warm armpits?

We received this question from Molatelo. Chris Smith asked physiologist Sam Virtue to strip down the science for us.

Sam - Okay. So this is the rooted in the fact that our bodies control our core body temperature extremely tightly. If you go a couple of degrees higher or a couple of degrees lower than 37 degrees as your core temperature you're in big trouble. But note I keep using the word 'core', that's because whilst your core which will be things like your heart and brain will stay at 37, things like your fingers and toes can cool down much much more because they're not critical for life, and so our body will even sacrifice them and you can lose toes and fingers from frostbite. So in winter if we go out in a cold environment what our body does is it tries to protect our core temperature by constricting the blood vessels that go to our fingers and our toes to keep more of that warmth inside.

Obviously though, we’re humans and we like to be in a temperature where we don't have to use energy to just make heat so we wrap up really warm. Now the body can constrict its blood vessels in seconds using the nervous system, but when you put loads of clothes on you actually have to actively take them off or put them on if you want to change the temperatures. So if you suddenly move from a very cold environment to a slightly warmer one or you start doing some exercise, your body goes from being too cold, to too hot and so it starts to kick in processes to lose heat so it doesn't become too hot - hypothermic. And that includes releasing all the blood into your freezing cold feet but a bit like when you turn a kettle on it doesn't instantly boil, it takes a little while for that hot blood to warm your warm your toes back up, but you’ll be sweating.