The origin of the red and white barber pole is associated with the service of bloodletting and was historically a representation of bloody bandages wrapped around a pole. During medieval times, barbers performed surgery on customers, as well as tooth extractions. The original pole had a brass wash basin at the top (representing the vessel in which leeches were kept) and bottom (representing the basin that received the blood). The pole itself represents the staff that the patient gripped during the procedure to encourage blood flow.
Others opine that the red, white and blue format in the United States may be an homage to the colours of the flag.
At the Council of Tours in 1163, the clergy was banned from the practice of surgery. From then, physicians were clearly separated from the surgeons and barbers. Later, the role of the barbers was defined by the College de Saint Come et Saint Damien, established by Jean Pitard in Paris circa 1210, as academic surgeons of the long robe and barber surgeons of the short robe.
After the formation of the United Barber Surgeon’s Company in England, a statute required the barber to use a blue and white pole and the surgeon to use a red pole. In France, surgeons used a red pole with a basin attached to identify their offices. Blue often appears on poles in the United States, possibly as an homage to its national colours. Another more fanciful interpretation of these barber pole colours is that red represents arterial blood, blue is symbolic of venous blood, and white depicts the bandage.
via Barber’s pole