1. Dehydration Slideshow: Symptoms, Tips to Stay Hydrated
2. Summer Skin Hazards Slideshow Pictures
3. Sun-Damaged Skin Slideshow Pictures

Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• Heat exhaustion facts
• What is heat exhaustion?
• What causes heat exhaustion?
• Who is at risk for heat exhaustion?
• What are the symptoms of heat exhaustion?
• When should a person seek medical care for heat exhaustion?
• How is heat exhaustion diagnosed?
• How is heat exhaustion treated?
• What are the complications of heat exhaustion?
• How can heat exhaustion be prevented?
• What is the prognosis for heat exhaustion?
• Patient Comments: Heat Exhaustion - Symptoms
• Patient Comments: Heat Exhaustion - Treatments
• Find a local Doctor in your town
• Heat Exhaustion Index

The body cools itself most efficiently by sweating and having that sweat evaporate. Should sweating be unable to meet the cooling demands of the body, heat-related illness can occur. This is a spectrum of conditions with minor symptoms such as prickly heat or heat rash, progressing to heat cramps, then heat exhaustion, and finally to heat stroke, a life-threatening medical condition.

The line between each diagnosis is not sharply drawn. Heat cramps describe involuntary spasm of the large muscles of the body, while heat exhaustion has more systemic complaints. These can include profuse sweating, weakness, nausea, vomiting, headaches, and muscle spasms. The affected individual may be a low grade fever. Heat stroke is a life-threatening situation where the body's cooling system fails. The body temperature spirals out of control usually greater than 106F (41C), sweating stops, and there are mental status changes like confusion, seizure, or coma.

Heat exhaustion occurs when a person exercises or works in a hot environment and sweating cannot dissipate the heat generated within the body. Often dehydration occurs because the person hasn't replaced the water lost by sweating.

Heat exhaustion occurs when a person exercises and works in a hot environment and the body cannot cool itself adequately. Dehydration occurs with water loss from excessive sweating, which causes muscle cramps, weakness, and nausea and vomiting. This makes it difficult to drink enough fluid to replenish the body's water supply, and the lack of body water impairs further sweating, evaporation and cooling.

Relative humidity is an important factor in developing heat exhaustion. If the humidity is too high, sweat on the skin cannot evaporate into the surrounding air and body temperature cooling fails.