The body’s natural response to cold exposure is to conserve heat by constricting blood vessels in the extremities (peripheral vasoconstriction), prioritizing the core organs. When moving to a warmer environment, the goal is to reverse this heat loss intentionally and gradually to avoid complications. A rapid, intense application of heat can cause a sudden rush of cold blood from the limbs back to the core, leading to an abrupt drop in internal temperature, known as “afterdrop.” Therefore, the rewarming process must be a measured series of actions designed to stop the immediate heat drain and slowly raise the core temperature back to its normal range.
Immediate Environmental Changes
The first step in safe rewarming is to eliminate the sources of continued heat loss. This begins with seeking a warm, dry, and sheltered location away from wind and cold surfaces. Moving to this protected environment prevents the body from expending metabolic energy on shivering and struggling against the elements.
Removing all wet clothing is necessary because water conducts heat away from the body about 25 times faster than still air. Damp material rapidly draws heat through evaporation and conduction, and changing into dry clothes stops this massive heat drain. If dry clothing is unavailable, wrapping the person in a dry blanket or towel creates an insulating layer.
If the person is only mildly cold and not severely hypothermic, gentle, non-strenuous movement can help by stimulating circulation and generating metabolic heat. This activity should be controlled and stopped before it causes sweating, since moisture from sweat would then evaporate and cool the body again.
Internal Core Temperature Boosts
Once the immediate environment is controlled, the body can generate heat internally through ingestion. Consuming warm, non-caffeinated, and non-alcoholic liquids is recommended for conscious individuals. Warm drinks, such as broth or herbal tea, provide a direct source of heat and help reduce shivering, which is a significant energy drain.
Alcohol must be avoided because it causes vasodilation, widening peripheral blood vessels and drawing warm blood away from the core to the skin, accelerating heat loss. Caffeine should also be avoided as it can act as a diuretic, contributing to dehydration and interfering with temperature regulation. Providing high-energy foods, particularly simple sugars or fats, gives the body the fuel needed to power metabolic processes and generate internal heat.
Safe External Warming Methods
After stopping heat loss and providing internal fuel, external heat should be applied strategically and gradually. Passive methods, such as dry blankets, sleeping bags, or specialized warming blankets, trap the body’s own heat and are effective for mild cold exposure. If another person is available, skin-to-skin contact wrapped inside a blanket can safely transfer body heat.
For more active warming, heat sources must be applied only to areas where major arteries run close to the skin’s surface: the neck, armpits, and groin. Applying warm (not hot) water bottles, chemical heat packs, or heating pads to these areas helps warm the core blood supply directly. These external heat sources must be covered with a cloth or blanket and never placed directly on bare skin to prevent burns, as cold-numbed skin may not register dangerous heat levels.
Warm water immersion can be used, but the water must be warm, not hot. When using a bath or shower, the trunk of the body should be warmed first to avoid the afterdrop phenomenon caused by a sudden influx of cold blood from the extremities. Rapidly immersing the entire body in hot water is dangerous and can lead to shock or a sudden drop in core temperature.
Recognizing Serious Cold Exposure
It is important to know when self-warming methods are insufficient and immediate medical help is necessary. Signs of moderate hypothermia include the stopping of shivering, slurred speech, confusion, and poor coordination. As the condition progresses, a person may become disoriented, drowsy, or lose consciousness.
Signs of frostbite (the freezing of tissue) include a lack of feeling in the affected area, and skin that appears waxy, white, or grayish-blue. The tissue may feel hard to the touch. If severe cold exposure is suspected, emergency services must be called immediately.
While waiting for medical assistance, a severely cold person should be handled gently to prevent cardiac arrhythmias. Avoid rubbing any cold or frostbitten areas, as this can cause severe tissue damage. Do not attempt to rewarm severely hypothermic individuals with intense heat, such as a fireplace or very hot water, as this can cause dangerous core temperature fluctuations and burns.