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November 24, 2009
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Heat Stroke

Medical Author: Melissa Conrad Stoppler, MD
Medical Editors: William C. Shiel, Jr., MD, FACP, FACR, Dennis Lee, MD

Doctor to Patient

How to Recognize a Heat–Related Illness

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Jay W. Marks, MD

Avoid Heat Emergencies, Keep HydratedDuring a heat wave, it's important to know and be able to recognize the signs and symptoms of a heat-related illness. There are different types of heat-related illnesses, ranging from those that cause temporary discomfort to the generally fatal condition known as heat stroke. In all heat-related illnesses, the symptoms appear when a person is exposed to extreme temperatures.

The following checklist can help you recognize the symptoms of heat-related illnesses:

  1. Heat Rash: Heat rash is a skin irritation caused by excessive sweating during hot, humid weather. It can occur at any age but is most common in young children. Heat rash looks like a red cluster of pimples or small blisters.
  1. Heat cramps: A person who has been exercising or participating in other types of strenuous activity in the heat may develop painful muscle spasms in the arms, legs, or abdomen referred to as heat rash. The body temperature is usually normal, and the skin will feel moist and cool, but sweaty.


Doctor to Patient

What is heat stroke?

Heat stroke is a form of hyperthermia, an abnormally elevated body temperature with accompanying physical and neurological symptoms. Unlike heat cramps and heat exhaustion, two forms of hyperthermia that are less severe, heat stroke is a true medical emergency that can be fatal if not properly and promptly treated.

The body normally generates heat as a result of metabolism, and is usually able to dissipate the heat by either radiation of heat through the skin or by evaporation of sweat. However, in extreme heat, high humidity, or vigorous exertion under the sun, the body may not be able to dissipate the heat and the body temperature rises, sometimes up to 106°F (41.1°C) or higher. Another cause of heat stroke is dehydration. A dehydrated person may not be able to sweat fast enough to dissipate heat, which causes the body temperature to rise.

Those most susceptible to heart strokes include:

  • infants,

  • the elderly (often with associated heart diseases, lung diseases, kidney diseases, or who are taking medications that make them vulnerable to heat strokes),

  • athletes, and

  • outdoor workers physically exerting themselves under the sun.

What are heat stroke symptoms?

Symptoms of heat stroke can sometimes mimic those of heart attack or other conditions. Sometimes a person experiences symptoms of heat exhaustion before progressing to heat strokes.

Symptoms of heat exhaustion include:

However, some individuals can develop symptoms of heat stroke suddenly and rapidly without warning.

Different people may have different symptoms and signs of heat stroke. But common symptoms and signs of heat stroke include:

  • high body temperature

  • the absence of sweating, with hot red or flushed dry skin

  • rapid pulse

  • difficulty breathing

  • strange behavior

  • hallucinations

  • confusion

  • agitation

  • disorientation

  • seizure

  • coma


Next: How do you treat a heat stroke victim? »

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Heat Stroke

What is dehydration?

The majority of the body is made up of water, with up to 75% of the body's weight due to H2O. Most of the water is found within the cells of the body (intracellular space). The rest is found in what is referred to as the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Total body water = intracellular space + intravascular space + interstitial space

Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water in the body. We lose water routinely when:

  • we breathe and humidified air leaves the body;
  • we sweat to cool the body; and
  • we urinate or have a bowel movement to rid the body of waste products.

In a normal day, a person has to drink a significant amount...

Read the Dehydration article »










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