Originally Cupping involved putting an animal horn on the body and creating a vacuum by orally sucking the air out. This in turn, bought toxic blood to the surface of the skin. Over time, other instruments were used glass cups. Cupping is not painful, however it can leave reddish patches on the skin, like circular bruises. Although these marks resemble bruises, the muscles have not been traumatised in any way. The redness on the skin indicates that there has been movement in the circulation of blood under and around the cups.