Gangrene follows necrosis (cell death), and is the decay of tissue, which then becomes black and/or green and malodorous. It is usually caused by frostbite, infection, ischemia (reduced blood supply), or thrombosis (blocked blood vessels). It is often associated with diabetes and long-term smoking. This condition is most common in the lower extremities. Treatment for gangrene is antibiotics and revascularization (restoration of blood flow), which can halt necrosis and allow healing. Other treatments include excision of the affected tissue and amputation.