Cupping therapy does leave round marks on your skin. These are not bruises as they do not indicate damage being done to the tissue. Rather, stagnant blood has been drawn to the surface to make way for oxygenated, nutrient rich blood. This is how healing occurs. Within that new blood are healing factors that correct trauma sustained by the tissue. The stagnant blood makes its way to your lymphatic system where it should eventually be eliminated from your body. It is important to drink water after a cupping session to make sure you properly flush the toxins trapped in that stagnant blood. These marks are the only side effect one should expect from a cupping session. They should not hurt, neither during or after, and they usually go away within 1-2 weeks.