Red, blue, white: There is a frightening story behind the colored stripes at the hairdresser. The history of barber's posts goes back far into the Middle Ages.
Bloodletting was a common treatment to cure illnesses from sore throats to the plague. In 1163, Pope Alexander III banned the clergy to carry out the intervention. The practice became too low-threshold for the clergy as they were needed for other more complex tasks. This is how the barber post we know today came into being.