Emergency advice

Heat exhaustion:

  1. Help them lie down out of the sun and raise their legs.
  2. Give them water to drink.
  3. Advise them to seek medical advice.

What is heat exhaustion?

Long periods in the sun can take its toll after a while and can lead to heat exhaustion. Heat exhaustion is caused by a loss of salt and water from the body, usually through excessive sweating.

It develops slowly and usually happens to people who aren’t used to hot, humid weather. If you’re at a festival, a sports match or an outdoor event and it’s very hot, it’s easy to suffer from heat exhaustion.  Prevention is best, so always try to stay well hydrated by drinking plenty of water (but not too much, drink to thirst), wear light and loose-fitting clothing and remember a wide-brimmed sun hat and sun cream. 

Try to keep out of the direct sun during the hottest part of the day, from 11am to 3pm.  Heat exhaustion isn't always caused by weather and can be a consquence of the body producing more heat than it case lose during vigorous and/or endurance exercise. 

Some prescribed medication can make people more susceptible to heal illness (eg, Selective Saratonin Reuptake Inhibitors like Sertraline and Trycyclic Antidepressants like Amitryptaline).  Recreational drugs such as ecstasy can also affect a person's ability to regulate their temperature.  It is important to spot and treat heat exhaustion, so that the more serious condition, heatstroke, doesn't develop.

Signs and symptoms

How to spot heat exhaustion:

  • Headache
  • Dizziness and confusion
  • Loss of appetite and feeling sick
  • Sweating with pale clammy skin
  • Cramps in the arms, legs and stomach
  • Fast, weakening pulse and rapid breathing

What to do

  1. Help them to lie down in a cool place and raise their legs.

  2. Give them lots of water to drink or isotonic sports drinks.

  3. Check their breathing, pulse and responsiveness.

  4. Suggest they get medical advice. Call 999/112 if you are concerned. 

Related first aid advice


Dehydration can develop into a more serious condition if left untreated. Find out what to look for and what to do.


Sunburn is caused by over exposure to the sun, or a sunlamp or sunbed. Find out what to look for and what to do.


If someone has heatstroke, your priority is to cool the casualty down as quickly as possible and get them to hospital. Find out what to look for and what to do.

St John Ambulance volunteers providing support