Signs and symptoms of frostbite include:

• At first, cold skin and a prickling feeling
• Numbness
• Red, white, bluish-white or grayish-yellow skin
• Hard or waxy-looking skin
• Clumsiness due to joint and muscle stiffness
• Blistering after rewarming, in severe cases

Frostbite is most common on the fingers, toes, nose, ears, cheeks and chin. Because of skin numbness, you may not realize you have frostbite until someone else points it out.

Frostbite occurs in several stages:

• Frostnip. Frostnip is a mild form of frostbite. Continued exposure leads to numbness in the affected area. As your skin warms, you may feel pain and tingling. Frostnip doesn't permanently damage the skin.
• Superficial frostbite. Superficial frostbite appears as reddened skin that turns white or pale. Your skin may begin to feel warm — a sign of serious skin involvement. If you treat frostbite with rewarming at this stage, the surface of your skin may appear mottled. And you may notice stinging, burning and swelling. A fluid-filled blister may appear 12 to 36 hours after rewarming the skin.
• Deep (severe) frostbite. As frostbite progresses, it affects all layers of the skin, including the tissues that lie below. Your skin turns white or bluish gray and you may experience numbness, losing all sensation of cold, pain or discomfort in the affected area. Joints or muscles may no longer work. Large blisters form 24 to 48 hours after rewarming. Afterward, the area turns black and hard as the tissue dies.

Frostbite occurs when skin and underlying tissues freeze. The most common cause of frostbite is exposure to cold-weather conditions. But it can also be caused by direct contact with ice, frozen metal or very cold liquids.

Specific conditions that lead to frostbite include:

• Wearing clothing that isn't suitable for the conditions you're in — for example, it doesn't protect against cold, windy or wet weather or it's too tight.
• Staying out in the cold and wind too long. Risk increases as air temperature falls below 5 F (minus 15 C), even with low wind speeds. In wind chill of minus 16.6 F (minus 27 C), frostbite can occur on exposed skin in less than 30 minutes.
• Touching materials such as ice, cold packs or frozen metal.

The following factors increase the risk of frostbite:

• Medical conditions that affect your ability to feel or respond to cold, such as dehydration, excessive sweating, exhaustion, diabetes and poor blood flow in your limbs
• Alcohol or drug abuse
• Smoking
• Fear, panic or mental illness, if it inhibits good judgment or hampers your ability to respond to cold
• Previous frostbite or cold injury
• Being an infant or older adult, both of whom may have a harder time producing and retaining body heat
• Being at high altitude, which reduces the oxygen supply to your skin

Complications of frostbite include:

• Increased sensitivity to cold
• Increased risk of developing frostbite again
• Long-term numbness in the affected area
• Excessive sweating (hyperhidrosis)
• Changes in skin color
• Changes in or loss of nails
• Joint stiffness (frostbite arthritis)
• Growth defects in children, if frostbite damages a bone's growth plate
• Infection
• Tetanus
• Gangrene — decay and death of tissue resulting from an interruption of blood flow to the affected area — which can result in amputation
• Hypothermia