The short version
- Rewarm frostbite in water at 37 to 39 °C (98.6 to 102.2 °F) for about 30 minutes, until the tissue is soft and pliable, a strong recommendation in the 2024 Wilderness Medical Society guidelines[2][1].
- Do not thaw if it could refreeze. Refreezing triggers more clotting and cell damage[2].
- Never rub frostbitten skin; air dry, use dry bulky dressings and give ibuprofen[2].
- Deep frostbite needs hospital care fast: clot-dissolving tPA is suggested within 24 hours and iloprost up to 72 hours[2].
Frostbite stages: superficial or deep
| Degree[2] | What you see | Outlook |
|---|---|---|
| First | Redness and numbness | No tissue death; damage usually not permanent |
| Second | Blisters with milky fluid | Possible lasting numbness and cold sensitivity |
| Third | Blue-grey skin, later a hard black scab | Long-term ulcers possible |
| Fourth | Hard, colorless tissue; muscle, tendon or bone frozen | Tissue turns black and can separate over months |
In the field, as the 2025 guideline summary notes, the simpler two-tier split is favored: superficial (first and second degree, little or no tissue loss) and deep (third and fourth, tissue loss expected)[2]. That split was created by William Mills, an Anchorage orthopedic surgeon whose 1960 and 1961 papers were the first clinical studies of rapid warming in warm water[3].
Who gets frostbite on the water
| Group, July 2023 to June 2024[4] | Frostbite |
|---|---|
| US Navy, active duty | Most common cold injury: 20 cases, 66.7% of Navy cold injuries |
| US Army, active duty | 125 cases, 45.5% of Army cold injuries |
| US Air Force, active duty | 47 cases, 67.1% |
The 2024 guidelines set frostbite risk at anything below 0 °C, with risk rising below −15 °C[2]. On a winter deck, spray and wind add to that cold exposure. Wet cold above freezing causes a different injury: trench foot[5].
Frostbite treatment on board, step by step
- Treat hypothermia and serious injuries first[2]; see cold water immersion survival.
- Decide: thaw now or not. If the part could refreeze before reaching shelter, do not thaw it; protect it and get the person out of the cold[2].
- Rapid rewarming: water at 37 to 39 °C for about 30 minutes, until the tissue is red and pliable[2].
- If a warm bath is impossible, let it thaw passively[2].
- Never rub. Air dry, then apply dry, bulky dressings and raise the limb[2].
- Ibuprofen, pain relief, fluids and tetanus cover are all in the guideline list[2].
- Blisters: clear ones may be drained; leave blood-filled blisters intact[2].
The 24-hour clock for deep frostbite
For severe frostbite, the guidelines suggest tPA within 24 hours of injury, and iloprost up to 72 hours, ideally as soon as possible[2]. Early tPA at a community hospital before transfer may reduce amputation[2]. Hard, grey or blood-blistered fingers at sea mean a medevac decision now, not at the next port call.
Prevention for winter crews
| Measure | Why |
|---|---|
| Keep blood flowing | Good nutrition and oxygenation, and no alcohol, interfering drugs or tight clothing[2] |
| Keep moving | Exercise is recommended to promote blood flow to the hands and feet[2] |
| Protect from the cold | One of the three main prevention strategies in the guidelines[2] |
| Warm water ready | Rapid rewarming needs a container and a thermometer to hold 37 to 39 °C[2] |
For Alaska operations, see Alaska fishing vessel medical compliance and commercial fishing vessel medical requirements.
Discovery Health MD writes cold-weather medical plans for winter fleets: maritime medical consulting for the frostbite and hypothermia protocol, and ship medical chest management for the thermometers, dressings and drugs behind it. Book a physician review of your winter crew plan.
Common questions
What is the best treatment for frostbite?
Rapid rewarming in water at 37 to 39 °C for about 30 minutes, if there is no risk of refreezing[2].
Should you rub frostbite?
No. The guidelines say never rub; air dry instead[2].
What are the stages of frostbite?
First to fourth degree, grouped in the field as superficial or deep[2].
Should you pop frostbite blisters?
Clear blisters may be drained; blood-filled blisters should be left intact[2].
When does frostbite need a hospital?
Deep frostbite needs fast transfer: tPA is suggested within 24 hours and iloprost up to 72 hours[2].
At what temperature does frostbite start?
The 2024 guidelines place risk below 0 °C, rising below −15 °C[2].
Is frostbite the same as trench foot?
No. Frostbite is freezing of tissue; trench foot needs moisture and happens above freezing[5].
