My Nose is Running when I'm the Only One That Should be Running!

Just imagine (I know its a stretch right now), that you are running outside on a cold day. Your body doesn't want to breathe in cold air to your lungs, so your nose tries its best to warm the air first, before sending it to the lungs. Tiny blood vessels inside your nostrils dilate, helping to warm up that air. While the dilation does help warm the air, it also increases mucus production! Isn't that nice ;)