While cupping is considered relatively safe (especially air cupping, which does not include the risk of fire and heat), it can cause some swelling and bruising on the skin. As the skin under a cup is drawn up, the blood vessels at the surface of the skin expand. This may result in small, circular bruises on the areas where the cups were applied. These bruises are usually painless, however, and disappear within a few days of treatment.
In addition, there are several instances where cupping should not be performed. Patients with inflamed skin; cases of high fever or convulsions; and patients who bleed easily, are not suitable candidates for cupping. Pregnant women should not have cupping on their stomach or lower back. If the cups are being moved, they should not cross bony areas, such as the ridges of the spine or the shoulder blades.