Heat exhaustion
The symptoms of heat exhaustion can develop rapidly. They include:
- very hot skin that feels ‘flushed’
- heavy sweating
- dizziness
- extreme tiredness (fatigue)
- feeling sick (nausea)
- being sick (vomiting)
- a rapid heartbeat
- mental confusion
- urinating less often and much darker urine than usual
A person with heat exhaustion should be moved quickly to somewhere cool and given fluids (preferably water) to drink. They should then begin to feel better within half an hour.
However, certain groups are more at risk of developing heatstroke or suffering complications from dehydration, and should be taken to hospital. This includes:
- children under two years old
- very elderly people
- people with kidney, heart or circulation problems
- people with diabetes who use insulin
Read more about treating heat exhaustion.
Heatstroke
The symptoms of heatstroke can develop over several days in vulnerable people, such as the elderly and those with long-term health problems, particularly in warm weather.
The symptoms of heatstroke develop more quickly when associated with physical activity. This type of heatstroke is referred to as exertional heatstroke. It usually affects young, active people.
Symptoms of heatstroke include:
- high body temperature – a temperature of 40°C (104°F) or above is often a major sign of heatstroke, although it can be diagnosed at lower temperatures and some people can reach these temperatures during physical exercise without developing heat exhaustion or heatstroke
- heavy sweating that suddenly stops – if the body is unable to produce any more sweat, it's a major warning sign that it has become over-heated and dehydrated
- a rapid heartbeat
- rapid breathing (hyperventilation)
- muscle cramps
The extreme heat that causes heatstroke also affects the nervous system, which can cause other symptoms such as:
- mental confusion
- lack of co-ordination
- fits (seizures)
- restlessness or anxiety
- problems understanding or speaking to others
- seeing or hearing things that aren't real (hallucinations)
- loss of consciousness
Heatstroke is a medical emergency. Dial 999 immediately to request an ambulance if you think that you or someone you know has heatstroke.
While waiting for the ambulance to arrive, move the person somewhere cool and give them fluids to drink (preferably water). You could also cool their skin with water by placing a damp flannel or sheet on them or spraying them gently.
It's better to wait for medical supervision before immersing someone fully in water because it could increase their blood pressure significantly (hypertensive response), which could be dangerous for those with cardiovascular disease or those at risk of stroke, such as the elderly.
Read more about treating heatstroke.
