Wednesday, 1 July 2009


Heat exhaustion and heatstroke are two, potentially very serious, heat-related health conditions.
Heat exhaustion

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

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

Left untreated heat exhaustion can progress to heatstroke.

Heatstroke occurs when a person’s core temperature rises above 40C (104F). At that temperature cells inside the body begin to break down and many of the important functions of the body stop working.

Symptoms of heatstroke can include mental confusion, rapid shallow breathing (hyperventilation) and loss of consciousness.

Heatstroke is a medical emergency. Left untreated heatstroke can cause multiple organ failure, brain damage and death.
Types of heatstroke

There are two main types of heatstroke:

* classic heatstroke, and
* exertional heatstroke.

Classic heatstroke

Classic heatstroke usually affects the elderly, infants and people with chronic health conditions and develops during unusually hot weather, such as during a heatwave.
Exertional heatstroke

Exertional heatstroke usually affects young active people who are engaged in strenuous physical activity for a long period of time in hot environments. For example, cases of exertional heatstroke have occurred in:

* athletes,
* people serving in the military, and
* fire-fighters.

How common is heat exhaustion and heatstroke?

It is hard to estimate exactly how common heat exhaustion is as many people do not report their symptoms to their GP.

Heat exhaustion is rare in England but there is evidence that the number of deaths amongst the elderly is much higher than usual during a heat wave.

If a person with heat exhaustion is taken quickly to a cool place and given plenty of water to drink they should begin to feel better within 30 minutes and experience no long-term complications. Without treatment, they could then develop heatstroke.

Heatstroke is a very serious condition and should be treated immediately. Treatment involves rapidly cooling the body to reduce the core temperature.

With rapid treatment, 90% of people with heatstroke will survive. Without rapid treatment, the survival rate can be as low as 20%; especially amongst vulnerable people, such as the elderly.

Heatwave alert: what it means

When temperatures soar health risks rise. A heatwave can be dangerous for the elderly, the very young and those who are ill. As the Met Office declares a heatwave alert, find out what you should do

Talk to NHS Direct on 0845 4647

(UK enquiry lines)

Textphone users can call 0845 606 4647

NHS Direct operates a 24-hour health advice and information service, providing confidential information on:

  • What to do if you or your family feel ill,
  • Health conditions and treatments,
  • Local healthcare services,
  • Self-help and support organisations.

Or email NHS Direct a health enquiry

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