Conditions · Emergency medicine and toxicology
Frostbite !
Freezing of skin and deeper tissue, most often of fingers, toes, ears and nose. Severe frostbite can kill tissue and end in amputation.
Updated 2026-11-01
Structures involved
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- Skin
- Dorsal hand arteries
- Digital arteries
- Digital nerves
- Distal phalanx, index finger
- Distal phalanx, middle finger
- Big toe
- Toe arteries
- Auricle
- Nasal cartilages
Why it happens
- Hypoxia, ischemia and reperfusion injury
- Thermal injury: burns, hyperthermia and hypothermia
- Causes of cell injury
- Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous
- Hypothermia and cold injury
- Skin blood flow
What it is
A cold injury in which tissue actually freezes, usually in the fingers, toes, ears, nose and cheeks. Ice crystals and blocked small vessels damage cells; after rewarming, swelling, blisters and, in deep injury, black dead tissue appear. Frostnip is the mild form with no tissue loss; non-freezing cold injuries such as trench foot are different.
Who gets it
Common in cold countries, among mountaineers, soldiers, homeless people and outdoor workers. In Colombia it is uncommon and seen mainly in climbers on high peaks and glaciers (Sierra Nevada del Cocuy, Nevado del Ruiz, Sierra Nevada de Santa Marta) and in people exposed in high páramo; it is relevant for travellers and mountain rescue teams.
Causes
- Exposure of skin to temperatures below freezing, worsened by wind and wet clothing
- Contact with very cold metal or volatile liquids
- Tight boots, gloves or rings that reduce blood flow
- High altitude, where hypoxia, dehydration and exhaustion add to the cold
Risk factors
- Alcohol or drug intoxication and mental illness
- Homelessness, inadequate clothing and immobility
- Smoking, diabetes, peripheral artery disease and Raynaud phenomenon
- Previous frostbite
- Hypothermia, dehydration and exhaustion
Pathophysiology
Cold first causes vasoconstriction of skin vessels to preserve core temperature. As tissue freezes, ice crystals form between cells, draw out water and damage membranes. On rewarming, damaged endothelium, platelet clumping and microthrombi block small vessels (reperfusion injury), so ischaemia and necrosis continue after the tissue is warm. Thawing followed by refreezing causes the worst damage.
Classification
- Frostnip: pale, numb skin that recovers fully on warming
- Superficial frostbite (first and second degree): redness and swelling, then clear blisters
- Deep frostbite (third and fourth degree): blood-filled blisters, hard grey-blue skin, necrosis of muscle and bone
- Severity is often graded after rewarming by how far the lesion extends along the finger or toe
Symptoms and signs
- Cold, numb, clumsy fingers or toes
- Pale, waxy or grey-white skin that feels hard to touch
- After rewarming: intense throbbing pain, redness and swelling
- Clear blisters (superficial) or blood-filled blisters (deep)
- Over days to weeks, a dry black shell (eschar) over dead tissue
Diagnosis
- Clinical
- Exposure history, examination before and after rewarming, assessment for hypothermia and other injuries. The final extent of tissue loss often becomes clear only after weeks.
- Tests
- Blood count, electrolytes, creatine kinase and kidney function in severe cases; screening for alcohol or other intoxication when relevant.
- Imaging
- Technetium bone scan or angiography in deep frostbite to show vessels and tissue without blood flow, which guides the use of clot-dissolving drugs and later amputation level.
Differential diagnosis
- Frostnip
- Non-freezing cold injury (trench foot, chilblains)
- Raynaud phenomenon
- Acute limb ischaemia from embolism or thrombosis
- Chemical burn from cold liquids or gases
Goal of treatment
Treat hypothermia first, rewarm the tissue quickly once there is no risk of refreezing, restore blood flow and delay amputation until the line of dead tissue is clear.
Treatment
- Acute
- Treat hypothermia and remove wet clothing and rings. Do not rub the area or use dry heat. Rapid rewarming in a warm circulating water bath only when refreezing can be avoided; pain relief during rewarming.
- Medical
- Analgesics and anti-inflammatory drugs, tetanus prophylaxis, elevation and gentle dressings; clear blisters may be drained and blood-filled blisters are left intact. In deep frostbite seen early, specialised centres use intravenous thrombolytics or a prostacyclin analogue to reduce amputations.
- Surgical
- Amputation or debridement usually delayed for weeks until the dead tissue is clearly demarcated, unless infection or wet gangrene forces earlier surgery; fasciotomy for compartment syndrome.
- Rehabilitation
- Physical and occupational therapy; footwear and prosthetic support after amputation.
Complications
- Gangrene and amputation of fingers, toes or limbs
- Wound infection
- Chronic pain, cold sensitivity and numbness
- Joint stiffness and growth plate damage in children
- Compartment syndrome and rhabdomyolysis in severe injury
Prognosis
Superficial frostbite heals without tissue loss. Deep frostbite often ends in some amputation, but early rewarming and early thrombolysis reduce the extent. Many people have long-term cold sensitivity.
Prevention
- Layered, dry clothing, insulated gloves, socks and hats; avoid tight boots
- Avoid alcohol and smoking in the cold; keep hydrated and fed
- Check fingers, toes and faces of companions regularly at altitude
- Descend or seek shelter early in bad weather
Test yourself
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How should frostbitten tissue be rewarmed?
Rapidly in warm circulating water once refreezing can be prevented; never by rubbing or with dry heat such as fires or heaters.
Why should tissue not be thawed in the field if it may refreeze?
Thawing followed by refreezing causes more tissue destruction than staying frozen until definitive rewarming.
Which blisters suggest deep frostbite?
Blood-filled (haemorrhagic) blisters, a sign of injury to deeper vessels; clear blisters suggest superficial injury.
Why is amputation usually delayed in frostbite?
Because the true limit of dead tissue takes weeks to declare itself; early surgery may remove tissue that would have survived.
Related conditions
- Accidental hypothermia
- Raynaud phenomenon
- Peripheral artery disease
- Acute limb ischaemia
- Acute compartment syndrome
- Burns (thermal, chemical, electrical; inhalation injury)
- Rhabdomyolysis
- Tetanus
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Frostbite (MedlinePlus, US National Library of Medicine, 2026).
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