Heat Illness


Heat illness is a spectrum of disorders due to environmental exposure to heat. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke. Heat illness can relate to many of the organs and systems including: brain, heart, kidneys, liver, etc.


A number of heat illnesses exist including:

  • Heat stroke - Defined by a body temperature of greater than 40 °C (104 °F) due to environmental heat exposure with lack of thermoregulation. Symptoms include dry skin, rapid, strong pulse and dizziness.
  • Heat exhaustion - Can be a precursor of heatstroke; the symptoms include heavy sweating, rapid breathing and a fast, weak pulse.
  • Heat syncope - Fainting or dizziness as a result of overheating.
  • Heat edema
  • Heat cramps - Muscle pains that happen during heavy exercise in hot weather.
  • Heat rash - Skin irritation from excessive sweating.
  • Heat tetany - Usually results from short periods of stress in intense heat. Symptoms may include hyperventilation, respiratory problems, numbness or tingling, or muscle spasms.


Prevention includes avoiding medications that can increase the risk of heat illness (e.g. antihypertensives, diuretics, and anticholinergics), gradual adjustment to heat, and sufficient fluids and electrolytes.


A 2016 U.S. government report said that climate change could result in "tens of thousands of additional premature deaths per year across the United States by the end of this century." Indeed, between 2014 and 2017, heat exposure deaths tripled in Arizona (76 deaths in 2014; 235 deaths in 2017) and increased fivefold in Nevada (29 deaths in 2014; 139 deaths in 2017).

Between 1999 and 2003, the US had a total of 3442 deaths from heat illness. Those who work outdoors are at particular risk for heat illness, though those who work in poorly-cooled spaces indoors are also at risk. Between 1992 and 2006, 423 workers died from heat illness in the US.

Exposure to environmental heat led to 37 work-related deaths. There were 2,830 nonfatal occupational injuries and illnesses involving days away from work as well, in 2015. Kansas had the highest heat related injury while on the job with a rate of 1.3 per 10,000 workers, while Texas had the most overall. Due to the much higher state population of Texas, their prevalence was only 0.4 per 10,000 or 4 per 100,000. Of the 37 deaths reported heat illnesses, 33 of the 37 occurred between the summer months of June through September. The most dangerous profession that was documented was transportation and material moving. Transportation and material moving accounted for 720 of the 2,830 reported nonfatal occupational injuries or 25.4 percent. After transportation and material moving, Production placed second followed by protective services, installation, maintenance, and repair and construction all in succession

Heat stroke is relatively common in sports. About 2 percent of sports-related deaths that occurred in the United States between 1980 and 2006 were caused by exertional heat stroke. Football in the United States has the highest rates. The month of August, which is associated with pre-season football camps across the country, accounts for 66.3% of exertion heat-related illness time-loss events. Heat illness is also not limited geographically and is widely distributed throughout the United States. An average of 5946 persons were treated annually in US hospital emergency departments (2 visits/ 100,00 population) with a hospitalization rate of 7.1%. Most commonly males are brought in 72.5% and persons 15–19 years of age 35.6% When taking into consideration all high school athletes, heat illness occurs at a rate of 1.2 per 100,000 kids. When comparing risk by sport, Football was 11.4 times more likely than all other sports combined to be exposed to an exertional heat illness.


Heat illness used to be blamed on a tropical fever named calenture.

See also

  • Occupational heat stress