Sweat evaporates from the skin to cool the body. If this personal cooling system does not work right or fails to work, heat exhaustion or a heat stroke can occur.

Heat exhaustion is a warning that the body is getting too hot. With a heat stroke, body organs start to overheat. They will stop working if they get hot enough. If it is not treated, a heat stroke can result in death.

Signs & Symptoms 

For a Heat Stroke

These signs and symptoms can occur suddenly with little warning:

  • Very high temperature (104ºF or higher).
  • Hot, dry, red skin. No sweating.
  • Deep breathing and fast pulse. Then shallow breathing and weak pulse.
  • Confusion. Hallucinations.
  • Convulsions.
  • Loss of consciousness.

  • For Heat Exhaustion
    Normal, low, or only slightly elevated body temperature.

    Cool, clammy, pale skin. Sweating.
    Dry mouth. Thirst.
    Fatigue. Weakness. Feeling dizzy.
    Nausea. Vomiting can occur.
    Muscle cramps.
    Weak or rapid pulse.


    Anything that keeps the body's natural cooling system from working right can lead to heat exhaustion and heat stroke. This includes:

  • Extreme heat and humidity.
  • Being in places without fans or air conditioners during hot, humid weather.
  • Not being able to get to public air-conditioned places. Waiting for a bus or other type of public transportation in hot, humid weather.
  • Overdressing.
  • Changes in the skin due to aging.
  • Poor circulation. Heart, lung, and/or kidney disease.
  • Not being able to sweat due to medicines, such as water pills and some used for mental illnesses.
  • Alcohol or drug use.
  • Any illness that causes weakness, fever, vomiting, or diarrhea.

  • Treatment

    A heat stroke is a medical emergency. Heat exhaustion may respond to self-care measures. If not, medical care is needed.

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