Heat Exhaustion

Heat exhaustion

Heat exhaustion is when the temperature inside the body, known as the core temperature, rises to 37-40°C (98.6-104°F).

At that temperature, the levels of water and salt in the body begin to drop. This causes symptoms such as nausea, feeling faint and heavy sweating.

If left untreated, heat exhaustion can sometimes lead to heatstroke.

The Symptoms:

The symptoms of heat exhaustion can develop rapidly. They include:

  • your skin feeling very hot and flushed,
  • heavy sweating,
  • dizziness,
  • fatigue,
  • nausea,
  • vomiting,
  • tachycardia (a rapid heartbeat), 
  • mental confusion, and
  • urinating less often and the colour of your urine being much darker than usual.

Vulnerable groups

Your sweat is controlled by part of the brain called the hypothalamus. The hypothalamus acts like a thermostat, producing more sweat when it detects that the body is getting hotter.

In some elderly people and people with chronic health problems such as diabetes, the hypothalamus does not work as well as it should. These people are more at risk of heat exhaustion and heatstroke.

Babies and young children are also more at risk because they sweat less.


At home

Heat exhaustion and heatstroke usually only happen in England during unusually hot weather such as a heatwave. The Department of Health has produced the following advice on how to prevent heat-related illnesses during a heatwave.

Stay out of the heat

  • Keep out of the sun between 11am and 3pm.
  • If you have to go out in the heat, walk in the shade, apply sunscreen and wear a hat and light scarf.
  • Avoid extreme physical exertion.
  • Wear light, loose-fitting cotton clothes.

Cool yourself down

  • Have plenty of cold drinks, but no caffeine and alcohol.
  • Eat cold foods, particularly salads and fruits with a high water content.
  • Take a cool shower, bath or body wash.
  • Sprinkle water over the skin or clothing, or keep a damp cloth on the back of your neck.

Keep your environment cool

  • Place a thermometer in your main living room and bedroom to keep a check on the temperature.
  • Keep windows that are exposed to the sun closed during the day, and open windows at night when the temperature has dropped.
  • Care should be taken with metal blinds and dark curtains, as these can absorb heat. Consider replacing or putting reflective material in between them and the window space.
  • Consider putting up external shading outside windows.
  • Have your loft and cavity walls insulated. This keeps the heat in when it is cold and out when it is hot.
  • Use pale, reflective external paints.
  • Turn off non-essential lights and electrical equipment, as they generate more heat.
  • Grow trees and leafy plants near windows to act as natural air conditioners.
  • Keep indoor plants and bowls of water in the house, as evaporation helps cool the air.
  • If possible, move into a cooler room, especially for sleeping.

Look out for others

  • Keep an eye on isolated, elderly, ill or very young people and make sure they are able to keep cool.
  • Ensure that babies, children or elderly people are not left alone in parked cars.
  • Check on elderly or sick neighbours, family or friends every day during a heatwave.
  • Be alert and call a doctor or social services if someone is unwell or further help is needed.

Travelling abroad

The advice above also applies if you are travelling abroad in a hot country.

Another important thing to remember is that it takes the body between a week and 10 days to adjust to a hotter environment. Before that time, you will sweat less than you should do. So until then, you should avoid doing any strenuous physical activity, even if you are very fit and healthy.

For more information go to: http://www.nhs.uk/Conditions/Heat-exhaustion-and-heatstroke/Pages/Introduction.aspx

Call 111 when you need medical help fast but it’s not a 999 emergencyNHS ChoicesThis site is brought to you by My Surgery Website