Heat exhaustion and heatstroke are both heat-related illnesses that share similar symptoms. They can cause headaches, nausea, confusion, and dizziness.

Although people can manage heat exhaustion with home remedies, heatstroke is a medical emergency. If a person is showing signs of heatstroke, it is important to seek immediate medical attention.

Without treatment, heat exhaustion can develop into heatstroke. Some signs of heatstroke include a high temperature, changes in mental function, and loss of consciousness.

Read on to learn the difference between the symptoms of these two conditions and what to do if they develop.

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Heat-related illnesses exist on a spectrum.

The most minor form is heat exhaustion. However, if a person does not manage heat exhaustion, it can progress to heatstroke and become a life threatening medical emergency.

Heat exhaustion symptoms

At the milder end of the spectrum, heat exhaustion may cause the following symptoms:

  • a headache
  • nausea
  • dizziness and weakness
  • irritability
  • thirst
  • heavy sweating
  • a raised body temperature
  • reduced urination

Heatstroke symptoms

Heatstroke is the most serious form of heat-related illness.

It may cause a person to:

  • develop a temperature of 106°F or higher within 10–15 minutes
  • become confused
  • experience a change in their mental function or have slurred speech
  • lose consciousness
  • have hot, dry skin or sweat profusely
  • have a seizure

In severe cases, if it goes untreated, heatstroke can be fatal.

When the body is unable to cool itself properly, people can experience a heat-related illness such as heat exhaustion or heatstroke. This can be due to summertime temperatures being hotter and more humid than usual in a particular location.

Usually, the body can cool itself by sweating, but in this type of extreme heat, the body’s inbuilt cooling mechanism may not be sufficient for some people.

Some people have a higher risk of heat-related illness than others. Certain health conditions increase a person’s chances of developing heat exhaustion or heatstroke.

They include:

People with the highest risk of heat exhaustion or heatstroke include:

  • athletes
  • people who work outdoors
  • people with long-term medical conditions
  • infants and children
  • people aged 65 years and older
  • people from low-income households

Becoming dehydrated or sunburned and drinking too much alcohol can increase a person’s risk of developing heat exhaustion and heatstroke, as can being on medication.

A 2018 study in the Journal of Intensive Care looked at a range of suggested blood vessel cooling devices, medications, and therapies for the treatment of heatstroke, but the authors found insufficient evidence to confirm their effectiveness.

However, the Centers for Disease Control and Prevention (CDC) provide first aid recommendations for both heat exhaustion and heatstroke.

If a person has heat exhaustion, the CDC advises:

  • getting them out of the heat
  • giving them liquids to drink
  • removing any unnecessary clothing, including shoes and socks
  • cooling them with cold compresses or washing their head, face, and neck with cold water
  • encouraging them to sip cool water

If a person has heatstroke, it is important to call 911 or the local emergency number. Then, move the person into a cool, shaded area and remove their outer clothing. Ways to cool them quickly include:

  • giving them a cold water or ice bath, if possible
  • wetting their skin
  • applying cold wet cloths to their head, neck, armpits, and groin
  • soaking their clothing with cool water
  • circulating the air to help their body cool faster

Heatstroke is a medical emergency that eventually leads to multi-organ dysfunction. It is essential to call 911 and stay with the person until medical help arrives.

Hot weather and exercise increase a person’s risk of heat exhaustion and heatstroke. A person can take steps to avoid these serious illnesses. These steps include:

  • consuming more cold drinks, especially when active or exercising
  • wearing light-colored, loose clothing
  • staying out of the sun during the hottest hours of the day
  • avoiding drinking alcohol
  • avoiding intensive exercise

If a person is inside their home on a very hot day, they can stay cool by:

  • closing the curtains or blinds
  • closing the windows if it is hotter outside than inside
  • turning off electrical equipment and lights that get hot

Heatstroke is the most serious heat-related illness. If a person does not receive emergency medical treatment for heatstroke, they can experience serious complications.

Heat exhaustion also poses serious health risks. Without management, it can progress to heatstroke.

The most important thing to do if someone is showing signs of heat-related illness is help them cool their body as quickly as possible. The more time that passes before a person receives treatment, the higher their risk of serious complications and death.

A person with heat exhaustion can eventually develop heatstroke if their condition goes untreated. Although both are heat-related illnesses that share similar symptoms, heatstroke can be life threatening and requires immediate medical attention.

Athletes, people who work outdoors, individuals with other health conditions, children, and older people are at the highest risk of heat-related illness. First aid should involve cooling the body as quickly as possible and calling 911 if a person has symptoms of heatstroke.