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Summer Dangers: Heat and the Body

Heat Index
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Heat and the Body
Staying Safe


How Heat Affects The Body

Human bodies dissipate heat by varying the rate and depth of blood circulation, and by losing water through the skin and sweat glands. When blood is heated above 98.6°F, the heart begins to pump more blood and the blood is circulated closer to the skin's surface so excess heat drains off into the atmosphere. At the same time, water diffuses through the skin as perspiration. The skin handles about 90% of the body's heat dissipating function. Sweating, by itself, does nothing to cool the body unless the water is removed by evaporation. High relative humidity hinders evaporation and reduces the cooling effects of perspiration.

Heat Disorders

Heat disorders generally result from a reduction or collapse of the body's ability to shed heat by circulatory changes and sweating, or a chemical imbalance caused by too much sweating. If the temperature of a body's inner core begins to rise, then heat related illnesses may develop. Ranging in severity, heat disorders share one common feature: the individual has been overexposed or over-exerted for his or her age and physical condition in the existing thermal environment. Those most at risk for heat disorders include the elderly, young, sick, or overweight.

What To Look For and Actions To Take:

Heat Disorder Symptoms First Aid
Sunburn Skin redness and pain, possible swelling, blisters, fever, and headache. Take a shower, using soap to remove oils that may block pores and prevent the body from cooling naturally. If blisters occur, apply dry, sterile dressings and get medical attention.
Heat Cramps* Painful spasms, usually in the leg and abdominal muscles. Heavy sweating. Get the person to a cooler place. Lightly stretch the affected muscle and replenish fluids with water. Do not give liquids with alcohol or caffeine as they can make the condition worse.
Heat Exhaustion Cool, moist, pale, or flushed skin. Heavy sweating. Headache, nausea, dizziness, weakness, and exhaustion. Get the victim to lie down in a cool place. Loosen clothing. Apply cool, wet clothes. Fan or move the victim to an air-conditioned place. Give sips of water. If nausea occurs, discontinue. If vomiting occurs, seek immediate medical attention.
Heat Stroke
(Sun Stroke)
High body temperature. Hot, red skin which may be dry or moist. Rapid, strong pulse. Changes in consciousness. Vomiting. Victim will likely not sweat. Heat stroke is a life-threatening condition. Call 911 immediately. Delay may be fatal. Carefully move victim to a cooler environment. If needed, continue rapid cooling by applying ice or cold packs wrapped in a cloth to the wrists, ankles, groin or armpits. Use extreme caution. Remove clothing. Use fans and/or air conditioners.

  *Heat Cramps are often an early sign that the body is having trouble with the heat.

Additional Information

American Red Cross
National Institutes of Health - Hyperthermia is the U.S. government's official web portal to all federal, state and local government web resources and services.