What is heatstroke?

Heatstroke is a life-threatening condition in which your body overheats and can no longer maintain a healthy temperature. You can avoid heatstroke by taking precautions in very hot weather.

Heatstroke occurs when your body temperature rises from its normal temperature to above 40°C. It can lead to serious organ damage or death if not treated urgently.

It is sometimes called hyperthermia.

What causes heatstroke?

Heatstroke is caused by your body not being able to cool down effectively. Sweat is your body's way to cool you down. Your body usually keeps its normal temperature through the evaporation of sweat and by moving more blood towards your skin.

What's the difference between heat exhaustion, heat stress and heatstroke?

Heat stress happens when your body gets too hot and needs to cool down. You might feel thirsty, tired, and sweaty.

Heat exhaustion is more serious. You feel very weak, dizzy, and might have a headache or nausea. Your skin may be clammy. To treat heat exhaustion, you need first aid that includes rest, fluids and a cool environment.

Heatstroke is the most serious. Your body isn't able to cool itself anymore, and your temperature becomes dangerously high. You might:

• stop sweating
• feel confused
• lose consciousness

What are the symptoms of heatstroke?

If you have heatstroke, you may experience:

• red, hot or dry skin
• a sudden rise in body temperature (above 40°C)
• no sweating or reduced sweating (though you may still be sweaty if you have been exercising)
• a dry, swollen tongue
• intense thirst
• seizures
• loss of consciousness

A person with heatstroke may also show unusual behaviours such as:

• slurred speech
• poor coordination
• aggressive or strange behaviour
• confusion

How do I know if I have heatstroke or heat exhaustion?

If you have heat exhaustion, you might have symptoms that are similar to heatstroke, but there are differences. In cases of heat exhaustion:

• Your body temperature will be normal or only slightly higher than usual.
• Your skin will be cool to touch, pale and clammy.
• Your body will continue to sweat, usually significantly.

To read more about the differences between heatstroke and heat exhaustion and the risks, read about hot weather risks and staying cool.

Why is heatstroke an emergency?

Heatstroke can lead to permanent disability and death. It may trigger sudden events such as a heart attack or stroke and can worsen existing medical conditions.

Heatstroke needs immediate first aid to lower your body temperature as quickly as possible.

Why might I get heatstroke?

Heatstroke happens after prolonged exposure to heat. It can occur when your body absorbs more heat than it can get rid of by sweating. Excessive sweating can also lead to dehydration if you are not drinking enough water to replace the fluid loss.

Your body will also try to cool down by redirecting blood flow to the skin, which means that your heart must work harder. This may lead to heart problems, especially if you have a heart condition.

You can get heatstroke indoors or outdoors. You can get heatstroke if you work or exercise in hot conditions without good air flow and if you don't drink enough water.

Am I at risk of heatstroke?

You are at higher risk if you have certain health issues, for example, if you:

• are affected by a chronic health condition or an infection
• take medicines or drugs that cause dryness or make you sweat less
• live with a chronic disease that affects how you sweat
• need to restrict your fluid intake (for example, due to a medical condition or fasting) and are unable to drink when you're thirsty

Some groups of people are also at higher risk, for example, people who are:

• very old or very young
• pregnant or breastfeeding
• living with overweight or obesity
• not physically fit
• homeless or isolated

Your work environment or living situation may put you at a higher risk of heatstroke. You are also more likely to suffer heat illnesses if you wear heavy, dark clothing on hot days.

What should I do if someone has heatstroke?

While you wait for the ambulance, try to cool the person down in any way you can:

• Give them sips of cool fluid if they are conscious.
• Lay them in a cool room or a shady place, and stay with them.
• Remove or loosen excess clothing.
• Sponge or spray them with cool water or cover them with wet towels or clothing and fan their damp skin.
• Place them in cool water or a cool shower if they are conscious.
• Place cold packs on their cheeks, palms and soles.

If they are unconscious, place them on their side with their mouth down and their chin up. You may need to do CPR.

Seek advice from a doctor before giving aspirin, ibuprofen or paracetamol to someone with heatstroke, as it will not help and can be harmful.

What should I do if I have heat exhaustion?

There are steps you can take to manage heat exhaustion and prevent symptoms of heatstroke getting worse.

• Find a cool place to rest.
• Drink cool water, a sports drink with electrolytes or an oral rehydration solution. Avoid caffeine and alcohol.
• Remove tight, heavy or excess clothing.
• Have a cool shower or use cold packs on your skin.
• Use a fan or air conditioning.

If you have heat exhaustion, it's a good idea to stay near someone, such as a friend or workmate, until you feel better.

How can I prevent heatstroke?

It's important to look after yourself and those around you in hot weather. Some things that you can do to stay safe in hot weather include:

• Drink plenty of water when it's hot, even if you're not thirsty. Avoid alcohol and hot or sugary drinks.
• Keep cool — try to avoid direct sun and wear lightweight, loose cotton clothing.
• Try not to be outside during the hotter parts of the day. If you do go out, try to go before 11am or after 5pm, wear a hat and take water.
• Be SunSmart — wear a hat, sunglasses, sunscreen and seek shade when you are outside.
• Keep your house cool — close windows and curtains during the day and keep them open at night. Use fans or air conditioning. If you don't have these at home, you can seek out places with air conditioning, such as public libraries and shopping centres.
• Take a cool bath or shower or sit with your feet in cool water to help you cool down.
• Have a plan — know who to call for help and ask your doctor what to do if you have any health conditions.

You can also take steps to prevent other people developing heatstroke:

• When it's hot, visit or phone friends, family and neighbours who are at risk to check that they're OK.
• Babies and young children are at a higher risk of developing heat-related illnesses. Keep children cool and give them lots of water to drink.
• Give babies under 6 months of age extra breastfeeds or formula feeds during hot weather. Do not give them water.
• Ensure pets have plenty of water and shade.
• Never leave children or animals alone in a car, even with the air conditioning on or windows open.

Resources and support

• Check the Bureau of Meteorology for warnings about hot weather.
• Visit the Australian Red Cross to learn more about heatstroke and heat exhaustion.
• For more information on staying well in hot weather, visit Beat the heat.
• Visit Pregnancy Birth and Baby to learn about dealing with hot weather during pregnancy and breastfeeding.
• Call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.