What is frostbite?

Our core body temperature is 36°C or 98°F. To maintain this temperature, our blood transports warmth all over the body. But, prolonged exposure to cold temperature can decrease our body's core temperature. Hence, in order to maintain the core temperature, our brain constricts the blood vessels of our limbs. It diverts the blood vessels to the vital organs to maintain the core temperature. As our limbs don't get sufficient warmth, they started to freeze, giving us frostbite.

                   Frostbite progresses in 3 stages. 
1. Frostnip - Our surface of the skin freezes. 
2. Superficial frostbite - often ice crystals formed in our skin. 
3. Deep frostbite - The underlying tissues, vessels, bones etc., freezes and permanently damaged.