Why Do I Blush at the Start of a Speech?

The mechanics of how a blush happens are straightforward. Underneath the skin of your face and neck is a lacework of tiny blood vessels called capillaries, which dilate under the influence of adrenaline to allow more blood and oxygen to flow. And a blush isn’t something you can fake. Unlike most human expressions, you can’t force a blush to appear on your face. (Or, sadly, demand that your capillaries shrink back to size.) (Read the full story)