Frostnip and frostbite are injuries caused by freezing of the skin and underlying tissues, most commonly the fingers, toes, nose, and ears. Frostnip causes the skin to turn pale, cold, and numb; there may also be tingling.
Frostnip does not cause permanent damage, but it may develop into frostbite if exposure to cold continues. In frostbite, the affected area becomes white, cold, and hard; it may then become red and swollen.
When rewarmed, mildly affected tissues become red, swollen, and sore. In more severe cases, blisters develop and the area becomes very painful. Severe frostbite may lead to gangrene (tissue death) or longer-term problems, such as persistent pain or loss of sensation.