Heat exhaustion

DEFINITION

Heat exhaustion is a condition whose symptoms may include heavy sweating and a rapid pulse, a result of your body overheating. It’s one of three heat-related syndromes, with heat cramps being the mildest and heatstroke being the most severe.

Causes of heat exhaustion include exposure to high temperatures, particularly when combined with high humidity, and strenuous physical activity. Without prompt treatment, heat exhaustion can lead to heatstroke, a life-threatening condition. Fortunately, heat exhaustion is preventable.

CAUSES

Your body’s heat combined with environmental heat results in what’s called your core temperature — your body’s internal temperature. Your body needs to regulate the heat gain (and, in cold weather, heat loss) from the environment to maintain a core temperature that’s normal, approximately 98.6 F (37 C).

Your body’s failure to cool itself

In hot weather, your body cools itself mainly by sweating. The evaporation of your sweat regulates your body temperature. However, when you exercise strenuously or otherwise overexert in hot, humid weather, your body is less able to cool itself efficiently.

As a result, your body may develop heat cramps, the mildest form of heat-related illness. Signs and symptoms of heat cramps usually include heavy sweating, fatigue, thirst and muscle cramps. Prompt treatment usually prevents heat cramps from progressing to heat exhaustion.

You usually can treat heat cramps by drinking fluids or sports drinks containing electrolytes (Gatorade, Powerade, others), getting into cooler temperatures, such as an air-conditioned or shaded place, and resting.

Other causes

Besides hot weather and strenuous activity, other causes of heat exhaustion include:

• Dehydration, which reduces your body’s ability to sweat and maintain a normal temperature
• Alcohol use, which can affect your body’s ability to regulate your temperature
• Overdressing, particularly in clothes that don’t allow sweat to evaporate easily

SYMPTOMS

Signs and symptoms of heat exhaustion may develop suddenly or over time, especially with prolonged periods of exercise. Possible heat exhaustion signs and symptoms include:

• Cool, moist skin with goose bumps when in the heat
• Heavy sweating
• Faintness
• Dizziness
• Fatigue
• Weak, rapid pulse
• Low blood pressure upon standing
• Muscle cramps
• Nausea
• Headache

When to see a doctor

If you think you’re experiencing heat exhaustion:

• Stop all activity and rest
• Move to a cooler place
• Drink cool water or sports drinks

Contact your doctor if your signs or symptoms worsen or if they don’t improve within one hour. Seek immediate medical attention if your body temperature reaches 104 F (40 C) or higher.