Heat exhaustion is a serious illness caused by too much heat. It is often brought on by overexertion or profuse sweating in a hot, humid, poorly ventilated environment.

During prolonged heat waves, the very young and the very old are also often at risk, even if they are not active.

If heat exhaustion is recognized and treated promptly, the effects can easily be reversed.

• Poor circulation, inefficient sweat glands, and other changes in skin condition brought on by the normal aging process
• Recent or recurrent illness accompanied by a fever
• Drugs and medications that increase heat production by the body or affect the body's ability to regulate its temperature. These can include diuretics, laxatives, antihistamines, amphetamines, and anti-depressants
• Living in a home without air conditioning or fans, excessive drinking of alcohol, overdressing, or excessive overeating

You cannot control the weather, but you can take these four steps to reduce your risk of heat exhaustion:

• During the spring and early summer months, acclimate your body to the increasing heat by gradually spending more time outdoors.
• Drink nonalcoholic fluids at regular intervals, whether you feel thirsty or not. When you are in the heat, drinking one half cup to one cup of fluids every 15 to 20 minutes will help keep you properly hydrated.
• Avoid being outdoors during the hottest part of the day. If you like to run or play sports, schedule your workouts in the early morning hours or after sunset. If you do not have air conditioning or cannot get to a place that is air conditioned, stay on the lowest floor and keep the shades drawn and a fan running.
• If you must be outside, wear lightweight, light-colored clothing. Eat light. Frequent small meals are better than a single heavy one.

Signs and symptoms of heat exhaustion include:

• Feeling weak, faint, or dizzy, with an accompanying headache or nausea
• Cold, clammy skin with ashen pallor
• Dry tongue and thirst
• Severe muscle fatigue
• Loss of appetite
• Profuse sweating
• Physical collapse, with muscle fatigue and sometimes cramping

The two basic steps in treating heat exhaustion are to replenish the body's lost fluids and to cool the body's temperature.

• Move the person into a cool place out of the sun.
• Loosen any tight-fitting clothing and remove any extra layers of clothing.

Offer the person fluids, such as water, fruit or vegetable juices, or sports drinks. Do not offer drinks that contain alcohol or caffeine. Encourage the person to drink about one half glass of fluid every 15 to 20 minutes.

Help the person cool off by sponging him or her with cool water, or by applying cool, wet cloths, such as towels or sheets.

In most cases, the person will begin to feel better within 30 minutes. If symptoms do not clear up or if the person begins to lose consciousness, call for emergency medical assistance.