Medicine: Fighting Frostbite

To most Americans, frostbite may seem like a remote risk. Yet as more and more people venture outdoors in winter—skiing, hiking, mountain climbing—it has become an increasingly common health hazard.

Fingers, toes or the nose and cheeks usually become vulnerable first. As the body tries to conserve heat for vital internal organs in bitter cold, it reduces the flow of warming blood to the extremities. Eventually, if the temperature in the tissue drops low enough, tiny ice crystals begin to form in the watery spaces between the cells. Expanding outward in all directions, the ice ruptures cell membranes and kills the tissue,...