Heatstroke first aid: symptoms, treatment and what to do in an emergency

Reviewed by the British Red Cross clinical team: 10 June 2026

What is heatstroke? 

Heatstroke occurs when someone becomes so hot it causes a failure of the brain’s thermostat, leading to the body becoming dangerously overheated. It is an emergency and needs medical help urgently. 

Symptoms of heatstroke

If you think someone has heatstroke, they may show the following signs or symptoms:

• body temperature over 40°C
• hot, flushed, and dry skin
• headache, dizziness and discomfort
• restlessness and confusion
• rapid worsening in the level of response
• full, bounding pulse

Heatstroke first aid: what to do if someone has heatstroke

Step 1: Move them to a cool place.

Step 2: Remove as much outer clothing as possible.

Step 3: Call 999 and ask for emergency help.

Step 4: Loosely wrap the person in a cold wet sheet and cool them by continually pouring cold water over it. If no sheet is available, you can fan them or sponge them with cool water.

Step 5: Continue to cool them, while waiting for help to arrive, until their temperature falls to 38°C.

Step 6: If their temperature returns to normal and they no longer feel hot to touch, you can stop cooling them. Replace the wet sheet with a dry one and help them to rest.

Step 7: Stay with them and ensure they are not getting worse.  If they start to heat up again, you can repeat the cooling process.

Learn heat-related first aid treatment for babies and children. 

Heatstroke vs heat exhaustion: key difference

Heatstroke is a failure of the thermostat. Their body is no longer able to effectively manage its own temperature. You will find they are hot with flushed dry skin.

In heat exhaustion, the body is struggling to manage due to loss of salts and fluids. They will appear paler than is normal for them, with clammy skin.

If you're unsure, help them to rest in a cool place and call 999 for emergency advice.  

Learn more about the differences between heatstroke and heat exhaustion.

What causes heatstroke?

Heatstroke can be caused by:

• spending a long time in a hot environment
• high fever
• heat exhaustion progressing to heatstroke
• use of drugs such as ecstasy
• sweating stops and can't cool the body itself

Who's at risk from heatstroke?

Anyone is at risk from heatstroke, but high risk groups include:

• young people
• older people
• people with certain health conditions, including certain chronic illnesses such as heart or lung disease or diabetes
• people working or exercising in the heat

What is the difference between heatstroke and sunstroke?

Sunstroke has the same symptoms as heat stroke but happens when your body overheats from too much sunlight. Heat stroke can happen when you're stuck inside a room without enough cool air.