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The difference between heat exhaustion and heatstroke

Woman fans herself
Heat stroke is serious. Would you know how to spot the signs?

Queenslanders know better than most just how hot summers can be. When it’s scorching outside, we switch on the air conditioners, keep our water chilled with ice, and slip, slop, slap, seek and slide. But when the mercury soars to extreme levels, we can get more than just hot and sweaty – heatwaves can put our health in danger.

In Australia, major heatwaves cause more deaths than bushfires, cyclones, earthquakes, floods and severe storms combined. As heatwaves are projected to last longer and occur more often, extreme heat could put more people at risk of harm.

It’s important to know how to care for our health when we’re faced with extreme heat. We’ve explored the symptoms of heatstroke and other heat-related illnesses, how to treat them, and tips for staying safe during heatwaves.

What is heat-related illness and what causes it?

Heat-related illnesses include heat cramps, heat exhaustion and heatstroke. These conditions can occur when we are exposed to extreme heat and our body can no longer cool itself or function effectively.

So how does it happen? Our body’s natural defence against overheating is sweating. Sweat evaporates from our skin and helps to cool us down. But in some situations, our body can’t sweat enough to stay cool, or sweating alone won’t combat the conditions we’re facing. When our body temperature rises to dangerous levels, it can be fatal.

Some of the factors that contribute to heat-related illness include:

  • Heatwaves – three or more days of high maximum and minimum temperatures that are unusual for the location or time of year
  • Overexercising, particularly in hot conditions
  • Wearing heavy, tight clothing in hot environments
  • Lack of airflow, confined spaces, and crowded conditions, such as concerts and sporting events
  • Exposure to radiant heat from bushfires
  • Being in a parked car, particularly in hot conditions.

Heat-related illness can affect anyone, but those at greatest risk include:

  • Older people, particularly the frail and those living alone
  • Babies and young children
  • People with existing medical conditions, such as heart disease
  • People on certain medications, especially fluid tablets
  • People on fluid-restricted diets
  • People who use recreational drugs.

Symptoms and treatment for heat-related conditions

If you recognise the signs and symptoms of any heat-related illness, it’s important to take action. Spotting the signs early helps to lower the risk of heatstroke, a condition that can cause permanent organ damage and potentially death, if untreated.

Anyone with a heart condition, diabetes, kidney disease, high blood pressure, or following a low sodium or fluid-restricted diet should seek medical help right away if symptoms of heat-related illness are present.

What to look for What to do
Heat rash
  • Clusters of bumps that look like red pimples or small blisters, usually on the neck and upper chest
  • Most common in young children
  • Move to a cooler place
  • Keep the affected area dry
  • Dusting powder may increase comfort
  • Avoid using ointments and creams
Can lead to heat exhaustion without prompt treatment
  • Increased thirst
  • Dry mouth, lips and tongue
  • Dizzy, tired or irritable
  • Headaches
  • Bright or dark yellow urine
  • Less urine than usual
  • Drink small amounts of water regularly
  • Move to a cooler place
  • Seek medical attention if symptoms are severe
Heat cramps
Can be an early warning sign of heat exhaustion
  • Muscle pains and spasms, usually in the abdomen, arms or legs
  • Most common in people who sweat a lot during strenuous activity
  • Stop all strenuous activity
  • Rest in a cool, shaded place
  • Increase fluid intake with water, low sugar sports drink or diluted fruit juice
  • After the cramps subside, wait a few hours before exercising strenuously
  • Seek medical attention if cramps continue for more than one hour
Heat exhaustion
Can lead to heatstroke without prompt treatment
  • Heavy sweating
  • Heat cramps
  • Paleness
  • Weak or dizzy
  • Nausea or vomiting
  • Fast, weak pulse
  • Headache
  • Rest in a cool, shaded place
  • Have a cool shower or bath, or apply cool, wet towels to the body
  • Loosen tight clothing
  • If fully alert, sip water or suck ice chips
  • Seek medical attention immediately if symptoms are severe, get worse or don’t improve with treatment, or last longer than an hour
This is a medical emergency – call Triple Zero (000) immediately

As per heat exhaustion, plus:

  • Worsening mental condition
  • Slurred speech, poor coordination
  • Seizures or losing consciousness
  • Call Triple Zero (000) immediately – this is a life-threatening emergency
  • Follow directions of ambulance staff
  • Move to a cool, shaded place
  • Remove excess clothing
  • Immerse in water, spray with hose, or apply wet cloths and fan vigorously

Preventing heat-related illness

Heat-related illnesses can be prevented. It’s important to be prepared for extreme heat, especially if you have existing medical conditions.

Remember to:

  • Stay hydrated
  • Stay out of the heat as much as possible
  • Keep your space cool with circulating air
  • Wear weather-appropriate clothing and protect yourself from sun damage
  • Rest often and save strenuous activities for the cooler parts of the day
  • Monitor for signs of heat-related illness and act promptly
  • Check in on others, especially those who are older, sick or frail.

Babies and young children are more vulnerable to the effects of extreme heat, as they can’t adapt easily to changing temperatures. Take extra steps to care for young children during hot weather, and never leave anyone (including pets) unattended in a car.

More information

Dehydration – the condition all Queenslanders need to be aware of

Four things to add to your summer survival kit

Sun safety and skin cancer

Survive the heat – Better Health Victoria

Last updated: 10 November 2021