Heat afflicts people of all ages. However, the severity of the reaction tends to increase with age - heat cramps in a 17-year-old may be heat exhaustion in a 40-year-old and heat stroke in a person over 60.

During periods of high temperatures and/or humidity, or while one is exposed to high interior temperatures, activity should be reduced as much as possible. When this cannot be done, emphasis should be placed on frequent rest periods and ample fluid intake.Thirst is a poor indicator of dehydration and there is not a warning sign for salt depletion. As a result, water intake during high temperature exposure must be forced. Studies have shown that even when adequate fluids are available, men will dehydrate by one to two quarts during exercise in high temperatures.

Food normally supplies enough salt. The use of salt tablets or solutions of commercial athletic drinks is usually not necessary. Rarely do people lose electrolytes (minerals such as sodium or magnesium). Moreover, commercial athletic drinks and salt tablets may increase thirst or cause severe nausea.

Acclimatization is another method of preventing heat-related illnesses. Everyone, regardless of physical condition, requires some time to acclimate to increased temperatures. The better one's physical condition, the less time necessary for acclimatization.

Other considerations to be taken during periods of high temperatures include decreasing physical activity during periods of highest daily temperature, alternating work and rest periods during the day and providing protection from direct sun exposure.

Types of heat-related emergencies

* Heat edema. Heat edema is exhibited in swelling of the feet and ankles. It usually presents no serious problem and requires no first aid or medical attention. However, these signs should not be confused with those of other more serious health problems, such as congestive heart failure.

* Heat syncope. This problem is usually self-correcting. The act of fainting and being placed in a lying-down position usually brings the return of consciousness. If no nausea and/or vomiting occurs, water can be given. Move the victim to a cooler environment, such as an air-conditioned building. Prolonged standing is usually the culprit in these cases.

* Heat exhaustion. This emergency has profuse sweating, along with nausea and perhaps vomiting. Headache, dizziness and profound fatigue may also be present. The victim's body temperature may rise above normal. Move the victim to a cooler environment and apply cool, moist towels to the body - especially to the head, neck, armpits.

* Heat cramps. Heat cramps result from the same fluid and electrolyte depletion that causes heat exhaustion. They can be very painful. Resting and stretching the affected muscle will help relieve the cramp. Moving to a cooler environment is also suggested.

* Heatstroke. The least common but most serious of the heat emergencies is heatstroke. This is a medical emergency and is associated with a 50 percent death rate. It happens when the thermoregulatory mechanisms of the body are overwhelmed and don't function.

Other signs and symptoms of heatstroke include: Hot, flushed skin - often dry; rapid breathing; loss of bowel and bladder control; rapid, weak pulse.

Treat the heatstroke victim with rapid cooling by whatever means is available. Avoid direct contact with ice to the skin, since frostbite can result. Covering the victim with wet blankets or towels will start the cooling process.

A person's medical conditions can contribute to having heatstroke. The very young and very old are at greatest risk. Heart disease increases the risk since the heart must increase output to skin and sweat glands as a result of the heat.