What happens when a body gets cold?

September 28, 2025 •

3 min read

When exposed to cold temperatures, the human body loses heat faster than it produces it, triggering a complex series of physiological responses. The body's immediate goal is to conserve heat and protect vital organs, but prolonged exposure can lead to serious conditions like hypothermia and frostbite. Understanding what happens when a body gets cold is crucial for recognizing the signs of danger and seeking help.

Quick Summary

The body's initial response to cold is to conserve heat by constricting blood vessels, causing shivering, and redirecting blood flow to the core. As core temperature drops, organ functions slow down, leading to confusion, slurred speech, and eventually unconsciousness, a medical emergency known as hypothermia. This article details the stages and risks involved.

Key Points

Initial Reaction: When a body gets cold, it begins to shiver and constrict peripheral blood vessels to conserve heat for vital organs, primarily the heart and brain.
Hypothermia Stages: Hypothermia progresses from mild symptoms like shivering and confusion to severe stages where shivering stops, and vital organs fail.
Localized Injuries: Prolonged exposure can lead to localized injuries such as frostbite (freezing tissue) and trench foot (damage from cold, wet conditions).
Affected Organs: As core temperature drops, the heart, nervous system, and brain functions are significantly impaired, which can lead to cardiac arrest and confusion.
First Aid Focus: First aid for hypothermia involves gentle handling, moving the person to warmth, removing wet clothing, and applying gradual heat to the core areas.
Prevention is Key: Effective prevention strategies include dressing in layers with moisture-wicking fabrics, staying active, and avoiding alcohol and caffeine in the cold.

The Body's Initial Response to Cold

When temperatures drop, the hypothalamus, the body's thermostat, triggers responses to conserve heat. The most noticeable is shivering, generating heat through muscle contractions. Peripheral vasoconstriction also occurs, narrowing blood vessels in extremities like hands and feet to maintain warm blood around vital organs. These are part of thermoregulation, the body's effort to keep its core temperature stable.

How Thermoregulation Works

Thermoregulation, managed by the hypothalamus, counters heat loss, which happens through radiation, conduction, convection, and evaporation. Vasoconstriction minimizes radiation heat loss, and shivering increases heat production.

The Dangers of Prolonged Cold Exposure: Hypothermia

If the body loses heat faster than it can produce it, core temperature falls below 95°F (35°C), leading to hypothermia, a medical emergency with three stages.

The Stages of Hypothermia

Mild Hypothermia (95°F to 89.6°F): Characterized by shivering, confusion, increased heart rate, and pale skin.
Moderate Hypothermia (89.6°F to 82.4°F): Shivering typically stops, and symptoms include slurred speech, impaired mental function, and slowed heart rate.
Severe Hypothermia (below 82.4°F): Most bodily systems fail, leading to unconsciousness, very slow or absent pulse, and potential cardiac arrest without immediate medical care.

Localized Injuries: Frostbite and Trench Foot

Cold can also cause localized damage.

Frostbite

Frostbite is freezing of skin and tissue, often affecting extremities due to reduced blood flow. Symptoms include numbness and pale skin, potentially leading to permanent damage.

Trench Foot

Trench foot results from prolonged exposure to cold, wet conditions, causing constricted blood vessels and tissue damage.

The Effect on Internal Organs

Dropping core temperature compromises vital organs like the heart, nervous system, and brain. This can cause dangerous heart rhythms, impaired judgment, and confusion.

A Comparison of Cold-Related Injuries


Feature	Hypothermia	Frostbite	Trench Foot
Body Part Affected	Whole body, specifically core temperature	Exposed skin and underlying tissue (e.g., fingers, toes, nose)	Feet (due to prolonged cold and wet exposure)
Temperature	Core temperature below 95°F (35°C)	Temperatures below freezing (0°F or -18°C) are high risk	Temperatures above freezing (up to 60°F) in wet conditions
Key Symptoms	Shivering, confusion, slurred speech, weak pulse, drowsiness	Numbness, pale/waxy skin, hardness	Redness, tingling, swelling, blistering
Mechanism	Loss of core body heat faster than it can be produced	Freezing of body tissues	Restricted blood flow due to wet, cold conditions
Severity	Can be fatal if untreated	Permanent tissue damage possible	Nerve and tissue damage, possibly gangrene

How to Prevent Cold-Related Illnesses

Preventing cold-related issues involves dressing in layers with appropriate materials, protecting extremities, staying hydrated, eating high-energy food, and avoiding alcohol and caffeine. Taking breaks indoors and seeking shelter from wind are also important.

Conclusion

When a body gets cold, it activates protective responses, but prolonged exposure can lead to serious conditions like hypothermia and frostbite. Recognizing symptoms and providing first aid is crucial. Taking preventative measures can help protect against dangerous effects. For more detailed medical guidance on treatment, consult official health resources such as the Centers for Disease Control and Prevention's winter weather safety page.

First Aid for Hypothermia

For someone with hypothermia, act quickly and gently: move them to a warm place, remove wet clothing, cover them with dry materials, and warm their core (chest, neck, groin). Offer warm, sweet, non-alcoholic drinks if conscious. Call 911 immediately and perform CPR if needed.

Seeking Professional Medical Help

Severe cold-related conditions require professional medical care. Medical interventions can include rewarming techniques and supportive care. Resuscitation efforts can be successful even in severe cases.

Frequently Asked Questions

The very first physiological response is peripheral vasoconstriction, where your blood vessels constrict to reduce blood flow to your extremities and conserve heat in your core. Shortly after, shivering begins to generate heat through muscle activity.

Shivering is an initial, positive sign that your body's heat-generating systems are still active and fighting the cold. It is a warning sign to get warmer, but if it stops, especially as the person's condition worsens, it can indicate a more serious stage of hypothermia.

Hypothermia is a systemic condition where the entire body's core temperature drops dangerously low, affecting all vital organs. Frostbite is a localized injury where body tissue, typically on the extremities, freezes.

You should not rub or vigorously massage a person with hypothermia, as this can force cold blood from the extremities back towards the heart, lungs, and brain. This rapid cooling of the core can trigger cardiac arrest, a phenomenon known as "afterdrop".

Alcohol can dangerously interfere with your body's response to cold. It causes blood vessels to dilate (vasodilation), making you feel warmer initially, but this actually accelerates heat loss. It also impairs judgment and can reduce the body's shivering response.

Both the very young and the very old are more vulnerable. Infants have a larger surface area to body mass ratio, while older adults may have a slower metabolism, less muscle mass, or chronic health conditions that impair thermoregulation.

In cases of severe hypothermia, handle the person gently and immediately call for emergency medical help. If trained, begin CPR and continue warming efforts, as victims who appear lifeless can sometimes be successfully resuscitated.