Cupping is a treatment technique designed to stimulate the flow of blood and Qi within the superficial muscle layers. It is used for sore muscles, tension, neck pain, and for treating the common cold by breaking up phlegm in the chest and releasing stagnation. It involves the application of glass cups with heat to create suction, thereby pulling heat or toxins out of the body while stimulating local blood circulation. They may be moved over an affected area or left in place. The use of cups can cause redness and bruising which is considered part of the healing process.