Gangrene is the death of human cells or tissues caused by a blockage of blood supply to a wound. If gangrenous tissue isn't removed, the affected limb eventually begins to rot. And if bloodless tissue should become infected by poisonous bacteria such as clostridium , results can be fatal. Young blowfly maggots are implanted directly onto a wound, where they eat dead flesh, clean out dead skin, and kill harmful bacteria that need injured tissue to survive. Once maggots reach their fill of dead and dying flesh, they're removed from the wound and new maggots are applied.
Blood can then flow throughout the tissue, promoting the growth of new flesh.
Maggots may not be the only healing creepy critters to have earned a foul rap. For 2,500 years, doctors have used blood-sucking leeches for bloodletting. In 1994, a woman's scalp was ripped off when her hair was yanked into moving machinery. Doctors performing micro-surgery at the University of Southern California reattached the scalp, but one area swelled with congested blood. They applied leeches, one at a time for eight days, to suck up stagnant blood.