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Heat stress and heat-related illness

"When summer temperatures start to rise, it's important to know how to prevent heat stroke. Look out for those who are vulnerable to heat stress or heat stroke, such as the elderly, the very young and the sick, because it's more difficult for them to maintain a normal body temperature. Avoid sun exposure on hot days, drink plenty of fluids, limit physical activity and stay in cool, well-ventilated areas."

Dr Christine Bennett, Chair, Medical Advisory Panel, Bupa Australia.

What is heat stress or heat stroke? 

Heat stress occurs when your body is unable to cool itself enough to maintain a healthy temperature. Normally, the body cools itself by sweating, but sometimes sweating isn't enough and the body temperature keeps rising.

Over-exertion in hot weather, too long in the sun or bushfire exposure, and exercising or working in hot, poorly ventilated or confined areas can increase your risk of heat stress. Heat can also make an existing medical condition worse, for example heart disease.

Severe cases of heat stress can lead to heat stroke, which is a life-threatening medical emergency.

Generally, symptoms of heat stress include nausea, headaches and cramps, and a body temperature between 37 and 39°C.

Heat stroke is a more serious condition caused by a failure in your body's natural temperature regulation. Heat stroke has similar symptoms to heat stress but is more severe and the person may seem confused or aggressive, have a fit or lose consciousness. There may also be rapid pulse, headache, dizziness and dry, red skin. Body temperature will be over 40°C.

Heat stroke can cause the blood to thicken and organs to be damaged, which can rapidly lead to organ failure and death. It is a medical emergency.

Who's at risk? 

Anyone can suffer from heat-related illness, but those most at risk are:

  • people aged over 65, particularly those living alone or without air-conditioning
  • babies and young children
  • pregnant and nursing mothers
  • people who are physically unwell, especially with heart or lung disease or high blood pressure
  • people on medications for mental illness.

Elderly people are more prone to heat stress because their body may not adjust well to sudden temperature change. They are also more likely to have a chronic medical condition and be taking medication that may interfere with the body's ability to regulate temperature.

Heat waves kill more people than any other natural hazard experienced in Australia. In 2009, a two-week heat wave in South Australia and Victoria caused at least 150 deaths and may have contributed to more than 370 deaths. Between the years 1803 and 1992, at least 4287 people died in Australia as a direct result of heat waves. This is almost twice the number of fatalities attributed to either tropical cyclones or floods over much the same time frame.

What causes heat stress? 

There are many factors which can cause heat stress and heat-related illness, including:

  • dehydration. To keep healthy, your body temperature needs to stay around 37°C. The body cools itself by sweating, which normally accounts for 70 - 80 percent of the body's heat loss. If a person becomes dehydrated, they don't sweat as much and their body temperature keeps rising.
  • lack of airflow. Working in hot, poorly ventilated or confined areas.
  • sun exposure. This is particularly an issue on hot days between 11am and 3pm.
  • hot and crowded conditions. People attending large events (concerts, dance parties or sporting events) in hot or crowded conditions may also experience heat stress that can result in illness.
  • bushfires. Exposure to radiant heat from bushfires can cause rapid dehydration and heat-related illness. If the bushfire occurs during the high temperatures of summer, this adds to the risk.
  • party drugs. Use of illicit drugs such as ecstasy and speed can raise body temperature and cause dehydration especially if mixed with alcohol and the heat of a dance party or club.

What are the symptoms of heat-related illness? 

Symptoms vary according to the type of heat-related illness. Babies and young children may show signs of restlessness or irritability and have fewer wet nappies. Older people may become lightheaded, confused, weak or faint.

Common symptoms include:

  • heat rash. Sometimes called prickly heat, this is a skin irritation caused by excessive sweating. It can occur at any age, but is most common in young children. It looks like a red cluster of pimples or small blisters. It's most likely to occur on the neck and upper chest, in the groin, under the breasts and in the elbow creases.
  • cramps. These include muscle pains or spasms, usually in the abdomen, arms or legs. They may occur after strenuous activity in a hot environment, when the body gets depleted of salt and water. They may also be a symptom of heat exhaustion.
  • dizziness and fainting. Heat-related dizziness and fainting results from reduced blood flow to the brain. Heat causes an increase in blood flow to the skin and pooling of blood in the legs, which can lead to a sudden drop in blood pressure. There can be a feeling of light-headedness before fainting occurs.

Heat stress is a serious condition that can develop into heat stroke. It occurs when excessive sweating in a hot environment reduces the blood volume. Warning signs may include:

  • paleness
  • sweating
  • rapid heart rate
  • muscle cramps, usually in the abdomen, arms or legs
  • headache
  • nausea and vomiting
  • dizziness or fainting.

Heat stroke is a medical emergency and requires urgent attention.

Heat stroke occurs when the core body temperature rises above 40.5°C and the body's internal systems start to shut down. Many organs in the body suffer tissue damage and the body temperature must be reduced quickly. Most people will have profound central nervous system changes such as hallucinations, coma and seizures.

As well as effects on the nervous system, there can be liver, kidney, muscle and heart damage. The symptoms may be similar to heat exhaustion but worse. The skin may feel dry and hot. There will be no signs of sweating. The person may stagger, appear confused, have a fit, or collapse and remain unconscious.

What can I do to help someone with heat-related illness? 

Treatment options vary according to the type of heat-related illness. Apply first aid and seek medical assistance immediately if you, or someone you are with, shows any sign of heat exhaustion or heat stroke. The first step for any heat-related illness is to move the person to a cooler, less humid environment. Other first aid measures are listed below.

Heat rash

  • Keep the affected area dry.
  • Try using unperfumed talcum powder to increase comfort.
  • Avoid using ointments or creams, as they keep the skin warm and moist and may make the condition worse.

Heat cramps

  • Increase fluid intake.
  • Rest for several hours before returning to activity.
  • Seek medical help if there's no improvement.

Dizziness and fainting

  • Get the person to a cool area and lay them down.
  • If fully conscious and no signs of heat stroke, increase fluid intake.

Heat exhaustion

  • Get the person to a cool area and lay them down.
  • Remove outer clothing.
  • Wet skin with cool water or wet cloths.
  • Increase fluid intake if they're fully conscious and show no signs of heat stroke.
  • Seek medical advice.

Heat stroke

Heat stroke is a medical emergency and requires urgent attention:

  • Call triple zero (000) for an ambulance.
  • Get the person to a cool, shady area and lay them down while you're waiting for emergency medical help.
  • Remove clothing and wet skin with water, fanning continuously.
  • Do not give the person fluids to drink.
  • Position an unconscious person on their side and clear their airway.
  • If medical attention is delayed, seek further instructions from ambulance or hospital emergency staff.

How do you prevent heat stress? 

Prevention is the best way to manage heat-related illness. Some tips to prevent heat stress include:

  • keep up your fluids. You need to drink more during hot weather, regardless of how active you are. Don't wait to drink until you're thirsty. Drink plenty of water or other cool, non-alcoholic fluids - check with your doctor if you're on limited fluids or diuretic medication (fluid tablets). Avoid alcohol or drinks that contain lots of sugar. Don't have extremely cold liquids, as they may cause stomach cramps.
  • avoid exposure to heat. Stay out of the sun as much as you can.
  • protect yourself outside. If you must be outdoors, remember to protect yourself from the sun. Follow the 'Slip, Slop, Slap' guidelines by covering exposed skin with lightweight clothes, using sunscreen and wearing a hat.
  • limit physical activity. Too much physical activity on a hot day can lead to heat stress. If you can, restrict activity to cooler times of the day (before 11am and after 3pm, generally).
  • avoid leaving children or pets in cars. Even on cool days, cars can heat up to dangerous temperatures very quickly. Children or pets left unattended in parked cars for even a few minutes are at risk of serious heat-related illnesses and possibly death. Never leave children or pets in a parked car, even if the windows are left open a fraction.
  • take it easy. Rest often and, whenever possible, stay indoors or in the shade.
  • stay cool. Keep air circulating around you. Use air-conditioning if possible. If you don't have air-conditioning, consider visiting an air-conditioned shopping centre or public library. Take a cool shower, bath or sponge bath.
  • keep up your energy levels. Eat regular, light meals.
  • watch out for others. Check at least twice a day on older, sick or frail people who may need help to cope with the heat.

Where to get help 

Contact your doctor if you, or someone you know, appears to be suffering from a heat-related illness.

In an emergency, call triple zero (000) for an ambulance.

Further information 

Sports Medicine Australia: Heat guidelines


Better Health Channel, Victoria Government. [online] Melbourne, VIC: State Government of Victoria. c1999-2010 [Last reviewed Dec 2010, accessed 30 Jun 2011] Available from:

Coates L. An Overview of Fatalities from Some Natural Hazards in Australia. In: Heathcote RL Cuttler C Koetz J (eds). Conference on Natural Disaster Reduction 1996: Conference Proceedings. Barton, A.C.T.: Institution of Engineers, Australia. 1996: 49-54.

Cooper M. Death toll soared during Victoria's heatwave. [Online] Melbourne, VIC: The Age. 6 Apr 2009 [Accessed 30 Jun 2011] Available from:

Department of Commerce. Worksafe: Heat stress. [online] Perth, WA: Government of Western Australia. [Last updated Sept 2010, accessed 9 Jul 2011] Available from:

Herbst J. Heat-related deaths: theory and Adelaide findings. Pathology. 2010; 42(S1): S25-28.

Occupational Safety and Health Administration (OSHA). Quick Card - Protecting workers from heat stress. [online] Washington, DC: OSHA. [Accessed 9 Jul 2011] Available from: (PDF, 2.4Mb)

Sports Medicine Australia (SMA). Hot weather guidelines for sporting clubs and associations and the physically active. [online] Mitchell, ACT: SMA. [Accessed 9 Jul 2011] Available from: (PDF, 61.7Kb)

Sports Medicine Australia (SMA). Beat the heat: playing and exercising safely in hot weather. [online] Mitchell, ACT: SMA. 2008 [Accessed 9 Jul 2011] Available from: (PDF, 3.7Mb)

Sunsmart and Smartplay. UV exposure and heat illness guide. [online] Melbourne, VIC. Feb 2010 [Accessed 9 Jul 2011] Available from: (PDF, 1.5Mb)

Woodford, N. Heat and fire deaths: overview and philosophy. Pathology. 2010; 42(S1): S25.

Last published: 30 July 2011

This information has been developed and reviewed for Bupa by health professionals. To the best of their knowledge it is current and based on reputable sources of medical research. It should be used as a guide only and should not be relied upon as a substitute for professional medical or other health professional advice.

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