How to Recognize a Heat-Related Illness

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Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Jay W. Marks, MD

During a heat wave, it's important to know and be able to recognize the signs and symptoms of a heat-related illness. There are different types of heat-related illnesses, ranging from those that cause temporary discomfort to the generally fatal condition known as heat stroke. In all heat-related illnesses, the symptoms appear when a person is exposed to extreme temperatures.

The following checklist can help you recognize the symptoms of heat-related illnesses:

1. Heat Rash: Heat rash is a skin irritation caused by excessive sweating during hot, humid weather. It can occur at any age but is most common in young children. Heat rash looks like a red cluster of pimples or small blisters.

2. Heat cramps: A person who has been exercising or participating in other types of strenuous activity in the heat may develop painful muscle spasms in the arms, legs, or abdomen referred to as heat cramps. The body temperature is usually normal, and the skin will feel moist and cool, but sweaty.

3. Heat syncope: Someone who experiences heat syncope (fainting) will experience the sudden onset of dizziness or fainting after exposure to high temperatures, particularly after exercising in the heat. As with heat cramps, the skin is pale and sweaty but remains cool. The pulse may be weakened, and the heart rate is usually rapid. Body temperature is normal.

4. Heat exhaustion: Heat exhaustion is a warning that the body is getting too hot. Those most prone to heat exhaustion include elderly people, people with high blood pressure, and people working or exercising in a hot environment. A person with heat exhaustion may be thirsty, giddy, weak, uncoordinated, nauseous, and sweating profusely. As with heat syncope and heat cramps, the body temperature is usually normal in heat exhaustion. The heart rate (pulse rate) is normal or elevated. The skin is usually cold and clammy.

5. Heat stroke: Heat stroke is a serious, life-threatening condition that occurs when the body loses its ability to control its temperature. Victims of heat stroke almost always die, so immediate medical attention is essential when problems first begin. In heat stroke, a person develops a fever that rapidly rises to dangerous levels within minutes. A person with heat stroke usually has a body temperature above 104 F (40 C), but the temperature may rise even higher. Other symptoms and signs of heat stroke may include confusion, combativeness, bizarre behavior, feeling faint, staggering, strong rapid pulse, dry flushed skin, and lack of sweating. Delirium or coma can also result from heat stroke.

While heat cramps, heat syncope, and heat exhaustion may all be present in mild degrees, you should always contact a doctor or seek emergency medical attention if the symptoms of these conditions are severe or worsen with time. Heat stroke is a true medical emergency. If a person has the symptoms of heat stroke, you should notify emergency services (911) immediately.