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Heat Exhaustion

Heat exhaustion is a heat-related illness that may occur after you've been exposed to high temperatures for several days and have developed dehydration, which is an inadequate or imbalanced replacement of the fluids and electrolytes you've lost through excessive perspiration.

There are two types of heat exhaustion:

Water depletion. Signs include excessive thirst, weakness, headache, and even loss of consciousness.
Salt depletion. Signs include nausea and vomiting, frequent muscle cramps, and dizziness.

Although heat exhaustion isn't as serious as another heat-related illness -- heat stroke -- it isn't something to be taken lightly. Without proper intervention, heat exhaustion can progress to heat stroke, which can damage the brain and other vital organs, and even cause death.

Symptoms of Heat Exhaustion

The most common signs and symptoms of heat exhaustion include:

confusion
dark-colored urine (which indicates dehydration)
dizziness
fainting
fatigue
headache
muscle cramps
nausea
pale skin
profuse sweating
rapid heartbeat

Treatment for Heat Exhaustion

If you or anyone else has symptoms of heat exhaustion, it's essential to immediately get out of the heat and rest, preferably in an air-conditioned environment. If you can't get inside, try to find the nearest cool and shady place.

Other recommended strategies include:

Drink plenty of non-caffeinated and non-alcoholic beverages.
Remove any tight or unnecessary clothing.
Take a cool shower, bath, or sponge bath.
Apply other active cooling measures such as fans or ice towels.

If such measures fail to provide relief within 30 minutes, contact a doctor because untreated heat exhaustion can progress to heat stroke.

After you've recovered from heat exhaustion, you'll probably be more sensitive to high temperatures during the following week. So it's best to avoid hot weather and heavy exercise until your doctor tells you that it's safe to resume your normal activities.

Risk Factors for Heat Exhaustion

Heat exhaustion is strongly related to the heat index, which is a measurement of how hot you feel when the effects of relative humidity and air temperature are combined. A relative humidity of 60% or more hampers sweat evaporation, which hinders your body's ability to cool itself.

The risk of heat-related illness dramatically increases when the heat index climbs to 90 degrees or more. So it's important -- especially during heat waves -- to pay attention to the reported heat index, and also to remember that the heat index is even higher when you are standing in full sunshine.

If you live in an urban area, you may be especially prone to develop heat exhaustion during a prolonged heat wave, particularly if there are stagnant atmospheric conditions and poor air quality. In what is known as the "heat island effect," asphalt and concrete store heat during the day and only gradually release it at night, resulting in higher nighttime temperatures.

Other risk factors associated with heat-related illness include:

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