Why does shame turn cheeks red?

For the human body, shame is a stressful situation. Under stress, adrenaline is produced. It is a hormone that comes into play, taking an active part in the "fight or flight" decision. Being worried, we get into a defensive position, as if defending ourselves. 

 

Adrenaline prepares the body to cope with danger: it intensifies the heartbeat, speeds up breathing, increases pupils to get as much visual information as possible. Circulation increases, blood vessels dilate. The skin on the face is the first to turn red, since it is thinner than the rest of the body.