FROSBITE

Frostbite is the damage to tissues from freezing ;The blood vessels contract and cause loss of oxygen to the affected body parts.And results formation of ice crystals within cells, rupturing the cells and leading to cell death.
It most commonly affects areas that are further away from the body core and have less blood flow. These include your feet, hands, nose, and ears.

There are three degrees of cold injury: frostnip, superficial frostbite, and deep frostbite.

The affected skin may be slightly flushed. The skin changes to white or grayish yellow as the frostbite develops. Pain is sometimes felt early but subsides later. Often there is NO pain; the part being frostbitten simply feels intensely cold and numb.

In superficial frostbite, there will be an area that looks white or grayish and the surface skin will feel hard but the underlying tissue will be soft. With deeper involvement, large blisters appear on the surface, as well as in underlying tissue, and the affected area is hard, cold and insensitive. Destruction of the entire thickness of the skin will necessitate skin grafting and will constitute a medical emergency, because gangrene may result from loss of blood supply to the injured part.