Heat Exhaustion


Heat exhaustion occurs when the body becomes overheated, typically due to exposure to high temperatures and/or strenuous physical activity. It is characterized by symptoms such as heavy sweating and a rapid pulse. Heat exhaustion is part of a spectrum of heat-related illnesses, ranging from mild heat cramps to severe heatstroke.

The body overheats when it cannot effectively cool itself down, which commonly happens during exercise or physical exertion in hot and humid conditions. Factors contributing to heat illness include high temperatures, humidity, and inadequate fluid intake. When fluids lost through sweat are not adequately replaced, dehydration can occur, increasing the risk of heat exhaustion.

Symptoms of heat exhaustion include dizziness, headaches, nausea, and muscle cramps, among others. Treatment involves removing the individual from the heat, allowing for rest, and ensuring adequate fluid intake. Prompt treatment is crucial to prevent progression to heatstroke, a potentially life-threatening condition. However, with proper precautions, such as staying hydrated and avoiding excessive heat exposure, heat exhaustion is preventable.


Prior to the onset of heat exhaustion symptoms, an individual may experience a red rash (heat rash) or heat cramps. These discomforting muscle cramps can impact any muscle, although it they commonly occur in the arms or legs.

Generally, signs and symptoms of heat exhaustion can manifest gradually or suddenly, such as:

  • Dizziness, light-headedness, blurred vision, and headaches
  • Moist, cool skin that gets goosebumps in the heat
  • Faint, quick pulse
  • Prolonged perspiration
  • Weakness, exhaustion, or syncope, or fainting
  • Orthostatic hypotension, or low blood pressure upon standing
  • Fever, typically measured at 100 degrees F.
  • Nausea and vomiting

If signs of heat exhaustion persist despite an hour of hydration and rest, immediate medical attention is necessary. Seek prompt help if there is an inability to drink water or retain fluids, a fever exceeding 103 degrees Fahrenheit, difficulty speaking, standing, or walking, profuse sweating, or if confusion or loss of consciousness occurs.

If one suspect heat exhaustion, cease all activity, find a cooler environment, and hydrate with cool water or sports drinks.


The body’s core temperature, typically around 98.6 F (37 C), is maintained through a balance of internal heat production and environmental influences. In hot weather, sweating facilitates heat dissipation, but during strenuous activity or high humidity, this mechanism may be less effective, leading to heat cramps characterized by heavy sweating, fatigue, thirst, and muscle cramps. Prompt treatment involving hydration with electrolyte-rich fluids like Gatorade, seeking cooler environments, and rest can mitigate heat cramps and prevent progression to more severe heat-related illnesses such as heat exhaustion.

In addition to hot weather and strenuous activity, heat exhaustion can also be caused by:

  • Dehydration, as it reduces the body’s capacity to sweat and maintain a regular temperature.
  • Alcohol consumption, which can impede the body’s ability to regulate its temperature.
  • Overdressing, especially in garments that hinder sweat evaporation.

Risk factors

Heat exhaustion and various forms of heat-related illnesses, collectively known as hyperthermia, are more prevalent than commonly believed. Heat exhaustion, particularly induced by physical exertion, occurs frequently on days characterized by high temperatures and humidity. Several risk factors contribute to the likelihood of experiencing heat exhaustion:

  • Age: Infants, children under 4, and adults over 65 face an increased risk due to the underdeveloped temperature regulation mechanisms in children and the diminished control over temperature in older adults, influenced by factors like illness or medication.
  • Alcohol consumption: Excessive alcohol intake leads to dehydration, amplifying the susceptibility to heat exhaustion. Moreover, alcohol impairs the body’s ability to regulate temperature effectively.
  • Lifestyle choices: Engaging in strenuous physical activity in hot, humid conditions elevates the risk of heat-related ailments. This risk escalates further if heavy clothing or equipment is worn, especially among individuals unaccustomed to such environments.
  • Obesity: Carrying excess weight disrupts the body’s temperature regulation, retaining more heat and exacerbating the risk of heat-related illnesses.
  • Medications: Certain prescription drugs, such as diuretics, chemotherapy medications, and beta blockers, can induce vomiting, diarrhea, or dehydration, increasing susceptibility to heat exhaustion. Additionally, medications for conditions like hypertension, allergies, or psychiatric disorders may compromise the body’s hydration and heat response mechanisms.
  • Abrupt temperature shifts: Sudden exposure to high temperatures without acclimatization, such as traveling from a cold climate to a warm one or encountering early heat waves, heightens the vulnerability to heat-related illnesses as the body lacks adaptation time.
  • Weight and overall health: Individuals with excess weight or specific health conditions like diabetes or heart disease face an elevated risk of heat exhaustion, emphasizing the correlation between obesity and certain medical conditions with susceptibility to hyperthermia.