Skin without cold damage is normal (1). Frostnip (2) is mild frostbite that irritates the skin, causing redness, prickling and a cold feeling followed by numbness. Frostnip doesn't permanently damage the skin and can be treated with first-aid measures. With superficial frostbite (3), your skin feels warm, a sign of serious skin involvement. A fluid-filled blister may appear within 24 hours after rewarming the skin. With deep frostbite (4), you may experience numbness. Joints or muscles may no longer work. Large blisters may form a day or two after rewarming. Afterward, the area turns black and hard as the tissue dies.