Frostbite

Key takeaways

• First signs: redness or pain in the skin
• Later signs: skin that is white or grayish-yellow, unusually firm or waxy, or numb
• Most useful single change: Get into a warm place as soon as possible.
• Commonest mistake: Rubbing or massaging the area.
• See a doctor if any of the signs under "When to get help" below apply to you.

Why it matters

It can cause permanent damage, and numb skin can be burned easily during rewarming.

The numbers, in one place

Published figures for Frostbite

Measure	Figure
First signs	redness or pain in the skin
Later signs	skin that is white or grayish-yellow, unusually firm or waxy, or numb
Higher risk	people with poor circulation and people who are not dressed for the cold
Often occurs with	hypothermia, which should be treated first

What helps

• Get into a warm place as soon as possible
• Put the affected area in warm, not hot, water
• Warm the area with body heat, for example fingers in an armpit
• Cover exposed skin with hats, scarves, mittens and water-resistant boots

What to avoid

• Rubbing or massaging the area
• Using a heating pad, heat lamp, fireplace or radiator to warm numb skin
• Walking on frostbitten feet or toes unless absolutely necessary

In depth

In the cold, your body protects its core by narrowing the blood vessels in your hands, feet and face. This keeps vital organs warm but leaves the extremities short of warm blood. If the skin and tissues get cold enough, ice crystals form in and around the cells. The ice damages cell walls directly, and the narrowed, sluggish blood vessels can develop tiny clots that cut off circulation. Much of the lasting damage comes from this loss of blood flow.

Frostbite develops in stages. The mildest form, often called frostnip, causes numbness and redness that recover completely with warming. Superficial frostbite involves the skin and may produce clear blisters after rewarming. Deep frostbite reaches the tissues underneath, and blisters may be filled with blood, a sign of more serious damage. In the most severe cases, tissue dies and turns dark and hard over the following days and weeks.

The full extent of damage is often not clear at first. Skin that looks bad on day one may recover more than expected, and areas that look fine may turn out to be worse. For this reason, doctors often wait for affected areas to declare themselves before considering surgery. Fast access to medical care after severe frostbite matters, because some treatments that help restore blood flow work best when given early.

Signs and symptoms

• Pins and needles, then numbness, in fingers, toes, ears, nose or cheeks
• Skin that feels hard, stiff or wooden to the touch
• Clumsiness in the hands that makes simple tasks difficult
• Throbbing or burning pain as the area rewarms
• Blisters appearing a day or so after rewarming
• Skin that turns dark blue or black in the days after injury

Causes and risk factors

• Exposure to temperatures below freezing, especially with wind
• Wet gloves, socks or boots, which pull heat from skin
• Tight boots, rings or clothing that restrict blood flow
• Touching cold metal or spilling fuel on skin in freezing conditions
• Smoking and conditions that reduce circulation, such as diabetes and peripheral artery disease
• Alcohol or drugs that impair judgment about cold
• Previous frostbite in the same area

How it is checked

Frostbite is diagnosed by examining the affected areas, usually after they have been rewarmed. Doctors look at color, sensation, whether blisters form, and what kind of fluid they contain. They also check for hypothermia and other injuries, which take priority. Photos taken over time help track how the tissue is changing.

For severe frostbite, specialists may order imaging tests that show blood flow in the fingers or toes, such as a bone scan. These help predict which tissue is likely to survive and guide decisions about medicines and, later, surgery. People with severe frostbite are often transferred to a burn center or another hospital with experience in cold injuries.

Related topics

• The Evidence on Burns and Scalds, Without the Hype (Emergency Care)
• The Evidence on Blood Clots, Without the Hype (Blood Health)
• What the Guidance Really Says About Feet and Diabetes (Foot Health)
• The Evidence on Diabetic Foot Care, Without the Hype (Diabetes)

Where to go next

• Frostbite for Beginners: Where to Start
• Answers to the Common Questions on Frostbite
• Weather Safety: The Complete Guide
• Wildfire Smoke: What Published Guidance Supports
• Hurricane Preparedness and Emergency Kits: Sorting the Evidence From the Noise

When to get help

Get medical care for any skin that stays numb, white or grayish-yellow, or that blisters after rewarming. Call 911 if there are also signs of hypothermia, such as confusion, slurred speech or a temperature below 95°F.

Where this comes from

• CDC — Preventing Frostbite
• American Red Cross — Winter Storm Safety

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.