Heat Exhaustion: Signs to Watch Out For, Prevention, and Treatment

Fact checked by Olga Sadouskaya, MD
Clinical Pharmacologist, Chief Medical Officer

Who doesn't love spending the day at the lake or hiking with friends on a summer's day?

Warm weather can be idyllic. However, climate change means many places are experiencing increasingly hotter summers and more frequent heat waves. If you're unprepared, scorching temperatures can put stress on your body and lead to heat illnesses like heat exhaustion.

In this article, we'll explore the causes, symptoms, and possible treatments for heat exhaustion in kids and adults. We'll also compare and contrast heat exhaustion and heatstroke, helping you to identify the signs before it's too late. Let's get started!

What is heat exhaustion?

Heat exhaustion is a common form of heat illness that occurs when your body overheats and is unable to cool down naturally. It's usually triggered by a combination of extreme heat, high humidity, and prolonged and vigorous exercise.

When your core body temperature rises, water and electrolytes get lost via excessive sweating.

If you don’t replace these fluids, your body loses the ability to cool down efficiently. This can lead to dehydration, low blood pressure, fatigue, headaches, muscle cramps, and weakness — which are all symptoms of heat exhaustion.

So, how do you know when heat exhaustion has become a problem?

Signs of heat exhaustion

While heat exhaustion isn't normally fatal, it's critical to identify it early. Doing so may save you or a loved one.

Common signs of heat exhaustion include:

  • A temperature of 98.6 F – 104 F (37 C – 40 C)
  • Excessive sweating
  • Fatigue and weakness
  • Thirst
  • Muscle cramps
  • A rapid, weak heartbeat
  • Cool, moist, and pale skin
  • "Prickly" skin
  • Low blood pressure
  • Dizziness and fainting
  • Headaches
  • Nausea
  • Dark yellow urine
  • Swollen feet or ankles from heat edema

In some people, heat exhaustion occurs within a short space of time. In others, symptoms develop over days. It's crucial to listen to your body, so you don't miss the early warning signs.

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What are the signs of heat exhaustion in kids?

Babies and young, active kids are particularly vulnerable during a heatwave. They can't regulate their temperature as quickly as adults, making them more likely to overheat.

The symptoms of heat exhaustion in kids are similar to those in adults, but they may not have the words to tell you how they feel. So, parents and caregivers need to take cues from the child's behavior.

Signs may include:

  • A fever
  • Increased irritability or tantrums
  • Fewer wet nappies
  • Pale, clammy skin
  • Goosebumps
  • Sleepiness
  • "Floppy" limbs

If you suspect your child has heat exhaustion, seek medical attention immediately to avoid complications.

What is the difference between heat exhaustion and heatstroke?

Heat exhaustion and heatstroke are often conflated. They're both forms of heat stress, and symptoms can overlap, which is why the two get confused. Generally speaking, they’re different stages of the same process, with heat exhaustion being the earlier and milder one. If you don't recognize the symptoms of heat exhaustion and treat it promptly, it can quickly lead to heatstroke — a more advanced and dangerous condition.

An older couple sitting in the shade to avoid heat exhaustion

So, how do you tell the difference between heat exhaustion and heatstroke?

Heatstroke — also known as hyperthermia — happens when your body temperature rises dangerously and uncontrollably. It triggers an inflammatory response and, if not treated in time, can cause complications like cellular damage and organ failure. It can even be fatal.

A high fever of 104 F–111.2 F, dry skin, vomiting, and nervous system dysfunction such as confusion and disorientation are all hallmarks of heatstroke. On the other hand, heat exhaustion is characterized by excessive sweating and damp, pale skin — and it doesn't change your mental state.

Other symptoms of heatstroke include:

  • Headaches
  • Dizziness, light-headedness, and fainting
  • Irritability
  • Delirium
  • Slurred speech
  • Seizures
  • Inability to sweat
  • A rapid, strong heartbeat
  • Rapid breathing
  • Shock
  • Loss of consciousness

Heatstroke typically requires hospitalization, while heat exhaustion can be treated at home in most cases.

What causes heat exhaustion?

The combination of extreme environmental temperatures and high humidity increases your risk of heat exhaustion.

Exercising outdoors and spending time in direct sunlight when the heat index is high is a recipe for heat exhaustion. The heat index refers to the combined effect of the outdoor air temperature and the humidity level. In other words, it's how hot it actually feels outside.

Other common triggers for heat exhaustion are:

  • A heatwave
  • Dehydration
  • Sunburn
  • Overexerting yourself in hot weather
  • Spending time in a stuffy, hot car
  • Being in a crowded environment with poor ventilation
  • Wearing tight, warm clothes in hot weather
  • Visiting a hot climate that you're not used to
  • Exposure to intense heat from bushfires
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Heat exhaustion can happen to anyone, but some people are more vulnerable. Factors that increase your risk of heat exhaustion include:

  • Age: Babies, children, and the elderly are more vulnerable to extreme heat.
  • Occupation: Athletes, firefighters, soldiers, farmers, and construction workers are at higher risk of heat exhaustion due to their strenuous jobs.
  • Underlying health conditions: Certain chronic health conditions make it more difficult for your body to adapt to heat. These include heart disease, respiratory illness, and diabetes.
  • Medication: Chronic medications like diuretics, laxatives, blood pressure medication, antihistamines, and beta-blockers may increase your risk of dehydration and overheating.

Knowing the causes and risk factors can help you protect yourself and your loved ones from heat exhaustion before the symptoms appear.

How to prevent heat exhaustion

Planning ahead during a heatwave and when traveling may help to prevent heat exhaustion before it starts.

Here are 8 lifestyle strategies to reduce your risk of developing heat exhaustion:

  1. Stay inside when the UV index is strongest. Seek refuge inside an air-conditioned room or building between the hours of 11 a.m. and 4 p.m.
  2. Take regular hydration breaks during the day. Aim to drink 2–3 liters of water per day – don't wait until you feel thirsty to hydrate. When exercising intensely or working outdoors, drink a cup of water or juice every half hour to support sweat production.
  3. Wear loose, lightweight clothes. Wearing loose clothing made from breathable fabrics allows your skin to release heat efficiently. It's particularly important to dress appropriately during strenuous exercise.
  4. Don't get sunburnt. Sunburn can trigger dehydration and heat exhaustion. Always wear a wide-brimmed hat outdoors and apply a broad-spectrum UVA/UVB sunscreen with an SPF of 30+ to your face and exposed skin.
  5. A man in the desert at risk of heat exhaustion
  6. Create shade. Take an umbrella with you to the beach or an outdoor event to block out the sun and keep you cool.
  7. Exercise with caution. The best way to prevent heat exhaustion while exercising is to stay well hydrated, rest frequently, and work out in an air-conditioned gym. Plan your exercise sessions during the coolest times of day – the early morning, late afternoon, or evening.
  8. Snack regularly. Eating nutrient-dense foods throughout the day improves hydration and helps to sustain your energy in the heat – fresh fruit, vegetables, and salads are ideal.
  9. Avoid enclosed spaces and hot cars. The temperature inside a poorly ventilated car can become dangerously high within minutes. Always ventilate your vehicle when driving on a hot day, park in the shade, and never leave children or pets in a hot car.

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Heat exhaustion treatment

If you suspect you have heat exhaustion, you must stop what you're doing immediately and rest. If you continue being active, you risk developing heatstroke.

Below are 4 action steps to help you stop heat exhaustion in its tracks.

1. Remove heavy clothing

Take off any tight, heavy clothes so sweat can evaporate and heat can radiate off your skin efficiently. Spritzing your skin with cool water and creating a breeze with an electric fan can help you cool down faster.

2. Go inside or seek deep shade

Getting out of the sun is essential to reverse heat exhaustion. An air-conditioned room or building is best. If this isn't possible, seek deep shade under a large tree or near a tall building.

Sit or lie down with your feet up in a cool area until you feel better.

3. Rehydrate immediately

Dehydration and heat exhaustion go hand in hand. Increasing your fluid intake with water, juice, smoothies, ice tea, coconut water, or sports drinks cools you down from the inside.

Take small, frequent sips to help you keep the liquids down.

When you feel the urge to go to the bathroom, this means your hydration level has recovered.

4. Apply cool water to your skin

Immersing your body in a cool bath or shower brings your body temperature down rapidly. You can also apply a wet washcloth or an ice pack to your pulse points, forehead, neck, back of your legs, and under your arms.

The sooner you can implement these strategies, the better!

Note: Please seek immediate medical attention if you don't feel better within 1 hour despite hydrating, resting, and cooling your body down.

In conclusion

Global temperatures are on the rise, so learning to identify the risks and warning signs of heat exhaustion and other forms of heat illness is vital.

The good news is the tips and strategies in this article will help you prevent and treat heat exhaustion so you can enjoy warm weather!

August 2, 2022