So What causes headaches? It is stress. Stress causes the muscle to be in contraction. Muscle under contraction reduces the efficiency of the blood flow. Not only does this causes headaches, sometimes even serious disease would result. Most of the headaches (not all) are caused by contraction of two muscles. Levator Scampula and Trapezius
These two muscle are closely related to the head. Massaging of these two muscle can relax them, and naturally increase the efficiency of the blood flow to the head, and thus reduce the headaches or even make them disappear.