Nipple torture is a popular form of breast torture. Nipple clamps (a type of sex toy) are often used. When they are attached to erect nipples they pinch them and restrict the blood flow. When they are removed, further pain may be caused by the return of normal blood flow.
In order to protect the breasts from damage, breast torture must be carried out within certain limits. For instance, a reduction in blood circulation can occur in bound breasts which may be problematic if the breasts are tied for a long period of time.