In the Middle Ages, hair was not the only thing that barbers cut. They also performed surgery, tooth extractions, and bloodletting.
French authorities drew a fine distinction between academic surgeons (surgeons of the long robe) and barber surgeons (surgeons of the short robe), but the latter were sufficiently accepted by the fourteenth century to have their own guild, and in 1505 they were admitted to the faculty of the University of Paris.
As an indication of their medical importance, Harry Perelman points out that Ambroise Pare, "The father of modern surgery and the greatest surgeon of the Renaissance," began as a barber surgeon.
The barber pole as a symbol of the profession is a legacy of bloodletting.
The barber surgeon's necessities for that curious custom were a staff for the patient to grasp (so the veins on the arm would stand out sharply), a basin to hold leeches and catch blood, and a copious supply of linen bandages.
After the operation was completed, the bandages would be hung on the staff and sometimes placed outside as advertisement.
Twirled by the wind, they would form a red lamp; white spiral pattern that was later adopted for painted poles. The earliest poles were surmounted by a leech basin, which in time was transformed into a ball.
One Interpretation of the colors of the barber pole was that red represented the blood, blue the veins, and white the bandages. These colors have been retained by the modern Barber-Stylist.