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Understanding Heat-Related Illness -- the Basics

What Are Heat-Related Illnesses?

Prolonged or intense exposure to hot temperatures can cause heat-related illnesses, such as heat exhaustion, heat cramps, and heat stroke (also known as sun stroke). As your body works to cool itself under extreme or prolonged heat, blood rushes to the surface of your skin. As a result, less blood reaches your brain, muscles, and other organs. This can interfere with both your physical strength and your mental capacity, leading, in some cases, to serious danger.

By reducing excessive exposure to high temperatures and taking other precautionary steps, most heat-related illnesses can be avoided. Those who work in hot or humid environments -- such as manufacturing plants, bakeries, or construction sites during summer months -- are most at risk. However, even long, hot afternoons at the beach can pose problems if warning signs are ignored.

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With prompt treatment, most people recover completely from heat-related illness. However, heat stroke can be deadly if not properly managed.

What Causes Heat-Related Illnesses?

Heat-related illness can strike anyone. But chronic alcoholics, the elderly, the young, the obese, and individuals whose immune systems may be compromised are at greater risk, as are individuals taking certain drugs, such as antihistamines, antipsychotic medications, and cocaine. High humidity also increases the risk of heat illness because it interferes with the evaporation of sweat, your body's way of cooling itself.

Heat exhaustion, heat cramps, and heat stroke all occur when your body cannot cool itself adequately. But each is slightly different.

Heat exhaustion occurs when the body loses large amounts of water and salt through excessive sweating, particularly through hard physical labor or exercise. This loss of essential fluids can disturb circulation and interfere with brain function. Individuals who have heart, lung, or kidney problems or are on low-sodium diets may be particularly susceptible to heat exhaustion.

As in heat exhaustion, heat cramps can strike when the body loses excessive amounts of fluids and salt. This deficiency, accompanied by the loss of other essential nutrients such as potassium and magnesium, typically occurs during heavy exertion.

Heat stroke, the most serious of the heat-related illnesses, occurs when the body suffers from long, intense exposure to heat and loses its ability to cool itself. In prolonged, extreme heat, the part of the brain that normally regulates body temperature malfunctions. This decreases the body's ability to sweat and, therefore, cool down. Those who have certain medical conditions that decrease the body's ability to sweat -- such as scleroderma or cystic fibrosis -- may be at greater risk of developing heat stroke.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on March 28, 2014

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