Cupping is a therapy whereby a suction is created with glass cups and attached on to the body, usually the area of the back. The cups can be attached to specific acupoints and left in place or they can be dragged across a skin surface that has been oiled. The suction creates a local congestion that stimulates the acupoints. Dragging the cups across an oiled surface releases the muscle layer and relieves muscular tightness and pain. It can have a releasing and relaxing effect similar to a deep tissue massage. Cupping warms and promotes the free flow of chi and blood in the meridians and diminishes swelling and pain. It is most often used for back pain. It can also help gastrointestinal disorders and lung problems, such as cough and asthma.