During the Middle Ages a new category of medical practitioner emerged. The Pope had banned the clergy from performing bloodletting (although they were welcome to receive it), and physicians were discouraged by the fact that feudal lords could have them executed in cases of malpractice. So bloodletting and other minor procedures moved into the hands of barber-surgeons. More craftsmen than medics, they established their own guilds and competed for respectability with apothecaries and physicians. They advertised with a symbol that endures to this day -- a red and white striped pole. The pole represents the stick patients would grab while being phlebotomized; the white stripes represent the bandages and the red stripes, the blood.
-- Douglas Starr