It's a common misconception, however, the marks left by the cups are not bruises. Bruising is caused by impact trauma leading to breakage of capillaries and a reactionary rush of fluids to the damaged location from the tissue injury. There is no compression in cup therapy. The marks if you do happen to get any are a positive stress on the body. The broken capillaries are the blood vessels stuck in the tissue which is lifted by the suction of the cups. They will heal. The body rushes blood to the specific area to jump start heal the area worked. The marks will last 3-5 days depending on the pigment of your skin. the fairer the skin the longer the marks will last. The darker the marks the more tension that area.