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First Aid & Emergencies

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Cold Exposure: Ways the Body Loses Heat - Topic Overview

The body loses heat through:

  • Evaporation of water from your skin if it is wet (sweating). If your clothing is wet, you will also lose some body heat through evaporation and through respiration (breathing) when the body temperature is higher than 99°F (37°C). During intense exercise, the body loses 85% of its heat through sweating.
  • Radiation (similar to heat leaving a woodstove). This normal process of heat moving away from the body usually occurs in air temperatures lower than 68°F (20°C). The body loses 65% of its heat through radiation.
  • Conduction (such as heat loss from sleeping on the cold ground). Heat is lost in air temperatures lower than 68°F (20°C). The body loses about 2% of its heat through air conduction. However, water causes more heat loss from the body than air does, so heat can be lost from the body very quickly when it is placed in cold water.
  • Convection (similar to sitting in front of a fan or having the wind blow on you). The body loses 10% to 15% of its heat through convection.

Heat loss through evaporation and respiration increases in dry, windy weather conditions.

Recommended Related to First Aid

Understanding Frostbite -- the Basics

Frostbite refers to the freezing of body tissue (usually skin) that results when the blood vessels contract, reducing blood flow and oxygen to the affected body parts. Normal sensation is lost, and color changes also occur in these tissues. Frostbite is most likely to affect body parts that are farther away from the body core and, therefore, have less blood flow. These include your feet, toes, hands, fingers, nose, and ears. There are three degrees of cold injury: frostnip, superficial...

Read the Understanding Frostbite -- the Basics article > >

Wet clothing greatly increases heat loss through conduction and evaporation.

Heat loss in cold, wet weather increases the risk for hypothermia and cold injury. Heat loss can occur in warm temperatures through conduction. Swimming or sitting in cool or cold water can cause the body to lose heat very quickly and increase the risk for hypothermia.

Hypothermia can occur quickly (within a few hours) or gradually over days and weeks depending on a person's age, overall health, and environmental conditions.

    WebMD Medical Reference from Healthwise

    Last Updated: November 14, 2014
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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