Medically Reviewed By William C. Lloyd III, MD, FACS
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What is heatstroke?

Heatstroke is the most severe form of heat illness, heat injury, or heat stress. Heat illness includes a continuum of conditions, with heat cramps being the mildest form. Heat exhaustion falls next in seriousness, followed by heatstroke. Left untreated, heat exhaustion can quickly turn into heatstroke. Heatstroke can also occur without any warning signs of heat exhaustion. Heatstroke is a medical emergency. It can cause organ damage and even death without immediate medical care.

Heat illness happens when the body is unable to cool itself adequately. Body temperature begins to rise. Without treatment measures to cool the body, body temperature can reach heatstroke levels within 10 to 15 minutes. In general, this means a core body temperature higher than 104 degrees Fahrenheit. This can lead to seizures, disorientation, and other life-threatening symptoms.

Anything that prevents your body from cooling can contribute to heatstroke. This includes environmental factors and personal factors, such as age, body composition, and medical conditions.

Heatstroke is a medical emergency. Seek immediate medical care (call 911) for any symptoms of heatstroke, then focus on first aid. Take steps to cool the body while waiting for emergency medical personnel: Go to shade or air conditioning, loosen or remove clothing, apply ice packs or cool water, and drink small sips of cool and clear fluids. If you are caring for someone with suspected heatstroke, only offer cool liquids if the person is alert enough to swallow without choking. Do not force liquids.

What are the symptoms of a heatstroke?

Recognizing the symptoms and signs of heatstroke can help save a life.

Common symptoms of heatstroke

The most common heatstroke symptoms include:

  • Body temperature of 104 degrees Fahrenheit or higher

  • Confusion, disorientation, or loss of consciousness

  • Dizziness, weakness, nausea, or severe headache

  • Rapid breathing and pulse

  • Flushed, hot, dry skin with a lack of sweat

  • Seizures

Heatstroke is a life-threatening medical emergency. Seek immediate medical care (call 911) if you, or someone you are with, have any symptoms of heatstroke.

What causes heatstroke?

Heatstroke occurs when the body can’t cool itself. Normally, the body reacts to becoming heated by starting to sweat. Sweat evaporates, which cools the skin. Anything that prevents this evaporation can overload the body’s ability to cool itself. This causes core body temperature to rise rapidly. Failing to replace moisture lost through sweating can cause dehydration, which worsens the situation.

What are the risk factors for heatstroke?

Several factors increase the risk of developing heatstroke including:

  • Age: Young children and elderly adults have a higher risk of developing heatstroke. People in these age groups can’t regulate body heat as well as healthy adults. These two groups are also more prone to dehydration.

  • Clothing and equipment: Wearing excess clothing during physical activity increases the risk of heatstroke. Dark colors, backpacks, heavy protective pads, and helmets also trap heat and hinder cooling.

  • Dehydration: Failing to replace fluids lost through sweat can keep your body from cooling properly. This can happen with even mild dehydration.

  • Environment: High air temperature, high humidity, low wind speed, and high sun exposure can hamper sweat evaporation.

  • Medical conditions: Chronic medical conditions, such as heart disease, can affect your body’s ability to cool down. Being obese also increases the risk because fat acts as insulation, making cooling more difficult. Fever, sickle cell trait, and poor physical conditioning can also contribute to heatstroke.

  • Medications: Certain medications can make it harder to stay hydrated or respond to heat. This includes alcohol, antidepressants, antihistamines, antipsychotic medicines, benzodiazepines, beta-blockers, diuretics, and stimulants.

Reducing your risk of heatstroke

Fortunately, heatstroke is preventable. It is also predictable because the risk is highest on hot, humid, sunny days. You may be able to lower your risk of heatstroke by:

  • Acclimating to physical activity in heat by increasing intensity and duration gradually over several weeks to allow your body to adjust

  • Avoiding alcohol and caffeine, which can contribute to dehydration, before (and during) physical activity

  • Drinking plenty of water or sports drinks with electrolytes before, during and after physical activity whether you feel thirsty or not

  • Scheduling outdoor activities during the morning or evening hours when it is coolest and rescheduling activities for extreme heat conditions

  • Taking frequent breaks and resting in shaded or air-conditioned areas

  • Using sunscreen and other sun protection to prevent sunburn, which affects your body’s ability to cool down

  • Wearing loose-fitting clothes that are lightweight and light-colored

  • Soaking yourself in water to help your body cool down if you must be out in hot weather

If you have a chronic medical condition or take medications that put you at risk, talk with your doctor about heatstroke. You will need to be vigilant for early signs of becoming overheated.

How is heatstroke treated?

Heatstroke treatment requires emergency medical care. It is not something you can manage at home.

For symptoms of heatstroke, call 911 for immediate medical assistance. Emergency personnel have the equipment necessary to rapidly cool the individual. They also stabilize the patient as much as possible to help prevent organ shutdown. A person with heatstroke also needs intravenous (IV) fluids to rapidly replenish lost electrolytes.

While you are waiting for help to arrive, you can give first aid to someone with heatstroke. The first step is to get them out of the heat by seeking shade or finding an air-conditioned indoor space. Then help them with the following strategies:

  • Lie down and elevate the feet.

  • Loosen or remove as much clothing as possible including backpacks, helmets, padding, and other protective equipment.

  • Sip small amounts of cool water or sports drinks if the person is alert enough to do so without choking.

  • Spray or put cool water on the skin or get the person into a cool bath.

  • Direct airflow over the skin using a fan.

  • Apply ice packs or towels soaked in cold water to the neck, armpits and groin.

What are the potential complications of heatstroke?

The longer core body temperature remains high, the higher the risk of complications from heatstroke. Heatstroke can be fatal without prompt treatment to lower body temperature. Serious complications are also possible, including shock, brain damage, and organ failure. In some cases, the organ damage is permanent.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Feb 10
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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