Cupping is an Chinese medicine technique that involves heating a small glass bowl or cup and then attaching it to naked flesh. The heat difference creates a vacuum which causes the skin to be pulled into it. This causes capillaries close to the surface of the skin to break and ultimately bruising. It is believed by practitioners that this somehow increases blood flow to the area and therefore stimulates healing. It was popularised during the 2016 Olympics by swimmer Michael Phelps who displayed visible cupping marks on his torso during the Games. Another famous advocate for cupping is Gwyneth Paltrow
Wet cupping first involves breaking or cutting the skin before the cup is placed over the wound. The suction causes profuse bleeding and is supposed to be drawing undisclosed 'toxins' from the body.
Though cupping is mostly harmless and any bruising will clear after a few days, the practice can increase the chances of infection and burning and could lead to permanent scarring if repeated too often.