Medicinal leeches are now making a comeback in microsurgery. They provide an effective means to reduce blood coagulation, relieve venous pressure from pooling blood, and in reconstructive surgery to stimulate circulation in reattachment operations for organs with critical blood flow, such as eye lids, fingers, and ears. The therapeutic effect is not from the blood taken in the meal, but from the continued and steady bleeding from the wound left after the leech has detached. The most common complication from leech treatment is prolonged bleeding, which can easily be treated, although allergic reactions and bacterial infections may also occur. Devices called “mechanical leeches” have been developed which dispense heparin and perform the same function as medicinal leeches, but they are not yet commercially available.