The Difference Between Heatstroke and Heat Exhaustion, and How to Treat Both

Learn how to spot the signs and stay safe in the heat
A person sits on a park bench with their hands on their hand while another person gives them water

Sultry summer days have you dreaming of fun in the sun. But those bright, sunny days can have a dark side. 

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“Heat illnesses can be very serious, and it’s important to recognize the symptoms,” says emergency physician Thomas Waters, MD. Dr. Waters shares what signs to watch for, and what you can do to prevent heat exhaustion and heatstroke.

Heatstroke vs. heat exhaustion: What’s the difference?

Heat exhaustion and heatstroke are types of heat-related illnesses. “People often talk about heat exhaustion and heatstroke as though they are separate things. But they exist on a spectrum from not-so-serious to significant emergency,” Dr. Waters says.

The spectrum of heat-related illnesses includes:

  • Heat rash: Also known as prickly heat, this red, stinging rash develops when you’re hot and sweaty. It’s most likely to show up in areas where sweat gets trapped, like inside your elbows and behind your knees.
  • Heat cramps: Painful muscle cramps can strike when you’re exercising in hot weather. They develop when you sweat so much that your body loses salts and fluids.
  • Heat exhaustion: More serious than heat rash or cramps, heat exhaustion occurs when your body can’t cool itself through sweating. Untreated, it can progress to heatstroke.
  • Heatstroke: Sometimes called sunstroke, heatstroke is the most severe heat-related illness. During heatstroke, your body temperature climbs quickly to dangerous levels. Often, people with heatstroke stop sweating. “The body’s mechanisms for dealing with heat are overwhelmed,” Dr. Waters says. “Without treatment, heatstroke can be deadly.”

Warning signs of heatstroke and heat exhaustion

Sweating is your body’s way of cooling itself down. But on hot, humid days, sweating might not be enough. That’s especially true if you’re working out or doing physical work in hot weather.

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Heat exhaustion and heatstroke both cause your body temperature to rise. That temperature spike goes hand in hand with several other symptoms.

Heat exhaustion symptoms

Here’s what to look for with regards to heat exhaustion:

  • High body temperature.
  • Rapid breathing and heart rate.
  • Muscle cramps.
  • Headache.
  • Dizziness or lightheadedness.
  • Pale skin.
  • Nausea and vomiting.
  • Weakness and fatigue.

Heatstroke symptoms

The main symptoms to be aware of for heatstroke are:

  • Confusion or agitation.
  • Hallucinations and an altered mental state.
  • Inability to sweat.
  • Dry, red skin.
  • Dizziness or fainting.
  • Slurred speech.
  • Very high body temperature (more than 105 degrees F).
  • Seizures.

Heatstroke risk factors

Anyone can experience heat illness in hot, humid conditions. But certain factors increase your risk:

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  • Age: The young and old are most vulnerable to heat exhaustion and heatstroke. “Babies, children and older adults are at greater risk,” Dr. Waters says.
  • Activity level: People working or exercising outside in the heat are more likely to develop heat-related illnesses.
  • Dehydration: If you’re dehydrated — from sweating a lot and not drinking enough to replace the lost fluids — you have a greater risk of developing heat illness. Drinking alcohol outside on a hot day can also increase the risk since it can contribute to dehydration.
  • Adaptation: Your body gets better at responding to heat over time. If you travel from a chilly winter climate to a tropical location, you might be at greater risk until your body adjusts to the heat. The same is true if you start a new workout routine in hot weather. “That’s why most states now have laws to make sure high school athletes gradually work up to doing strenuous exercise in hot weather,” Dr. Waters says. “It takes time for your body to acclimate to the heat.”

How to avoid heatstroke and heat exhaustion

Heat exhaustion and heatstroke are no joke. But even when it’s sweltering outside, there are ways to stay safe. “Heatstroke is preventable, as long as you make the right moves,” Dr. Waters says.

  • Drink up: Dehydration increases the risk of heat-related illness, so drink plenty of water when the mercury climbs.
  • Take five: Most cases of heat exhaustion and heatstroke occur when people are exercising or working outside in hot conditions. If possible, avoid intense exercise and long stretches of activity on steamy days. “Pay attention to the weather. If it’s hot, sunny or humid, take frequent breaks,” he says.
  • Chill out: If you notice signs of heat exhaustion, get to a cool area ASAP. “Ideally, get into the air conditioning, but at least into the shade,” Dr. Waters says.
  • Pay attention: “It’s important for parents, coaches, school staff and others to pay attention to what’s going on around them,” Dr. Waters says. People don’t always recognize the signs of heat illness in themselves. So if you notice symptoms in others, help them get to a cool, shady place. If symptoms get worse, seek medical attention.

Get cool: Heat exhaustion and heatstroke treatment

If you have any signs of heat exhaustion, get out of the heat as quickly as you can. Swig some water to rehydrate and take steps to bring down your body temperature. “To cool your body, apply ice packs to the neck, armpits and groin,” Dr. Waters says. “You can also squeeze a rag of cool water over yourself to help you cool down.”

If you continue to feel sick — or notice signs of heatstroke, especially neurologic symptoms such as confusion, stumbling or clumsiness — call 911. Emergency room doctors have several methods to cool your body quickly and will monitor you for complications of overheating, such as damage to organs. “Heatstroke is an emergency. It can become deadly very quickly,” Dr. Waters says.

If you’re battling heat, don’t try to be a hero. “Heatstroke isn’t something you can just push through, no matter how strong you are,” he adds. “The most important thing you can do is pay attention to the warning signs and listen to your body.”

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