Heat exhaustion and heatstroke can develop when the body becomes too hot and struggles to control its temperature. Heat exhaustion usually improves when the person is moved somewhere cool, given fluids and actively cooled. Heatstroke is much more serious and is a medical emergency.

Knowing the difference matters.

Someone with heat exhaustion may be hot, thirsty, weak, dizzy and sweating heavily. Someone developing heatstroke may become confused, uncoordinated, agitated, have a seizure or become unresponsive.

If you suspect heatstroke, call 999 and start cooling the casualty immediately.

What Is Heat Illness?

Our bodies constantly produce heat and need to release it to maintain a safe internal temperature.

This normally happens through mechanisms including sweating and increased blood flow to the skin.

Problems can develop when the body gains or produces heat faster than it can lose it.

This may happen because of:

hot weather
prolonged sun exposure
strenuous exercise
physical work
high humidity
heavy or protective clothing
inadequate fluid intake
working in a hot environment

Heat illness can range from relatively mild problems such as heat cramps through to life-threatening heatstroke.

Two conditions first aiders should particularly understand are heat exhaustion and heatstroke.

What Is Heat Exhaustion?

Heat exhaustion happens when someone becomes too hot and their body is struggling to cope, often alongside significant loss of water and salts through sweating.

It can affect someone during hot weather, but it can also develop through strenuous physical activity.

Heat exhaustion is not usually an emergency if the person responds to cooling and begins feeling better.

However, it should not be ignored.

Without appropriate action, heat exhaustion can progress to heatstroke.

What Are the Symptoms of Heat Exhaustion?

Signs and symptoms can include:

tiredness
weakness
dizziness
feeling faint
headache
feeling sick or vomiting
heavy sweating
intense thirst
pale or clammy skin
muscle cramps
fast breathing
a fast heartbeat
raised body temperature

Someone experiencing heat exhaustion may simply say that they feel extremely hot, weak or unwell.

Children can experience similar symptoms and may also become irritable, sleepy or unusually floppy.

Heat Exhaustion First Aid

If someone develops signs of heat exhaustion:

1. Move Them Somewhere Cool

Get the casualty away from the heat.

Move them into:

shade
an air-conditioned building
a cool room
another cooler environment

Help them rest.

2. Remove Unnecessary Clothing

Remove unnecessary outer clothing to help the body lose heat.

This could include:

jackets
jumpers
excess layers
protective clothing where it is safe to remove it

Loosen restrictive clothing.

3. Give Them Fluids

If they are fully conscious and able to drink safely, encourage them to drink.

Suitable options include:

cool water
a sports drink
an oral rehydration drink

These can help replace fluids lost through sweating.

Do not give drinks to someone who is becoming significantly confused, very drowsy or unable to swallow safely.

4. Cool Their Skin

Actively help the casualty cool down.

You can:

spray or sponge the skin with cool water
fan them
use wrapped cold packs around areas such as the neck or armpits

Stay with the casualty and continue monitoring them.

How Quickly Should Heat Exhaustion Improve?

Someone with heat exhaustion should begin to cool down and feel better within approximately 30 minutes.

Continue to monitor them during this period.

If they are not improving, their symptoms become more serious or you are concerned about their condition, seek medical advice.

NHS 111 can provide advice for heat exhaustion that is proving difficult to manage.

However, if you suspect the casualty has developed heatstroke, call 999.

What Is Heatstroke?

Heatstroke occurs when the body’s ability to control its temperature becomes overwhelmed and the person’s core temperature rises dangerously.

This can cause serious damage to the brain and other organs.

Heatstroke is a medical emergency.

Unlike uncomplicated heat exhaustion, you should not simply give the casualty a drink and wait to see whether they improve.

They need rapid cooling and emergency medical help.

What Are the Signs of Heatstroke?

Suspect heatstroke if someone exposed to heat or strenuous activity develops signs such as:

confusion
agitation
disorientation
lack of coordination
unusual behaviour
a seizure
reduced responsiveness
loss of consciousness

Other possible signs include:

very high body temperature
fast heartbeat
fast breathing
shortness of breath
hot skin

A person may also still be unwell after approximately 30 minutes of treatment for suspected heat exhaustion.

The important warning sign is a change in brain function or behaviour.

Confusion, disorientation, seizures or reduced consciousness in someone who is dangerously hot should make you think about heatstroke.

Do People with Heatstroke Always Stop Sweating?

No.

This is an important point because older first aid information sometimes gives the impression that someone with heatstroke must have hot, dry skin and cannot be sweating.

Do not rule out heatstroke simply because the casualty is still sweating.

This is particularly important in exertional heatstroke, where someone may still be sweating heavily.

Look at the casualty’s overall condition, particularly their mental state and neurological symptoms.

What Is Exertional Heatstroke?

Exertional heatstroke develops during or following strenuous physical activity.

It can affect people such as:

runners
athletes
military personnel
outdoor workers
people performing demanding physical work
people exercising intensely

Importantly, exertional heatstroke does not require extremely hot weather.

A person can generate a large amount of heat through intense exercise or physical activity even when the surrounding temperature does not appear particularly dangerous.

Someone who becomes confused, collapses or develops other neurological symptoms during strenuous activity should therefore be treated seriously.

Heatstroke First Aid

If you suspect heatstroke:

1. Call 999

Heatstroke is a medical emergency.

Call 999 immediately.

If another person is available, ask them to make the emergency call while cooling begins.

Do not unnecessarily delay cooling while waiting for the ambulance.

2. Move the Casualty Away from the Heat

Move them into shade or another cooler location where possible.

3. Remove Excess Clothing

Remove unnecessary clothing to expose as much skin as reasonably possible and help heat escape.

4. Start Active Cooling Immediately

Current UK resuscitation guidance emphasises rapid cooling.

Use the most effective cooling method that is immediately available.

For suspected heatstroke, the priority is to bring the person’s temperature down as quickly as possible.

Is Cold-Water Immersion Recommended for Heatstroke?

Yes.

Current Resuscitation Council UK guidance describes whole-body cold-water immersion as the gold-standard cooling technique for heatstroke where it is practical and can be carried out safely.

The casualty is immersed from the neck down in cold water while their airway and condition are carefully monitored.

This method is particularly relevant to organised environments where exertional heatstroke is a recognised risk, such as:

endurance sporting events
military activities
some outdoor workplaces
organised physical training

However, cold-water immersion may not be practical in every emergency.

The important principle is:

Start effective cooling immediately using the best method available.

What If Cold-Water Immersion Is Not Available?

Do not delay cooling because you do not have an ice bath.

Alternative cooling methods can include:

a cold shower
spraying or misting the casualty with water
continuously wetting the skin while fanning
cold wet sheets
ice sheets
suitable cold packs
cooling vests or jackets
other available active cooling methods

Use what you have available and keep cooling while waiting for professional help.

Cool First, Transfer Second

An important principle in current heatstroke management is:

Cool first, transfer second.

This does not mean delaying the 999 call.

Call for emergency help immediately.

It means that when heatstroke is suspected, effective cooling is an urgent treatment and should begin as soon as possible rather than waiting until the casualty reaches hospital.

Where practical, cooling should continue while arrangements are made for transfer and during transport when appropriate.

How Long Should You Cool Someone with Heatstroke?

In organised environments where an appropriate core temperature can be measured, Resuscitation Council UK guidance recommends cooling until core temperature falls below 39°C.

However, most members of the public and workplace first aiders will not have appropriate equipment to accurately measure core temperature.

Where a suitable core temperature measurement cannot be obtained, current guidance recommends continuing active cooling for approximately 15 minutes or until neurological symptoms resolve, whichever occurs first.

Follow the instructions of the ambulance service.

Should You Give Someone with Heatstroke a Drink?

A person with straightforward heat exhaustion who is fully alert and able to swallow can be given cool fluids.

Heatstroke is different.

Someone who is confused, drowsy, having seizures or becoming unresponsive may not be able to swallow safely.

Do not give a drink to somebody who cannot safely drink.

Concentrate on:

calling 999
rapid cooling
monitoring their airway and breathing
following ambulance service instructions

Should You Give Paracetamol for Heatstroke?

No.

Heatstroke is not the same as having a fever caused by an infection.

Medicines such as paracetamol are not a first aid treatment for heatstroke.

The priority is rapid physical cooling and emergency medical treatment.

What If the Casualty Has a Seizure?

Heatstroke can cause seizures.

If the casualty has a seizure:

protect them from immediate danger
do not restrain them
do not put anything in their mouth
move dangerous objects away
protect their head where possible
continue cooling as safely as circumstances allow
follow the instructions of the ambulance service

Call 999 if this has not already been done.

What If Someone with Heatstroke Becomes Unresponsive?

Monitor their breathing carefully.

If they are unresponsive but breathing normally, protect their airway and continue monitoring them while waiting for the ambulance.

If appropriate, place them in the recovery position while continuing cooling as far as practical.

If they are unresponsive and not breathing normally, cardiac arrest should be suspected.

Call 999 if this has not already been done and start CPR.

Our guide to Basic Life Support explains how to recognise cardiac arrest and respond.

You can also read our Seven Steps of CPR guide.

Heat Exhaustion vs Heatstroke

Although the conditions are connected, there is an important difference.

Heat Exhaustion

Someone may have:

weakness
dizziness
headache
nausea
thirst
muscle cramps
heavy sweating
pale or clammy skin

Move them somewhere cool, remove excess clothing, give fluids if they can drink safely and actively cool them.

They should start improving within around 30 minutes.

Heatstroke

Someone may develop:

confusion
agitation
disorientation
lack of coordination
seizures
reduced responsiveness
loss of consciousness

This is an emergency.

Call 999 and start rapid active cooling immediately.

Do not wait 30 minutes if the casualty already has signs of heatstroke.

Who Is More at Risk from Heat Illness?

Anyone can develop heat illness, particularly during strenuous activity.

Some people may be more vulnerable, including:

babies and young children
older people
people with long-term health conditions
people taking certain medicines
people working outdoors
athletes
people performing strenuous physical activity
people wearing heavy clothing or protective equipment
people who are dehydrated
people unused to hot conditions

Alcohol can also contribute to dehydration and impair someone’s ability to recognise that they are becoming unwell.

Heat Illness in Babies and Children

Children can become affected by heat relatively quickly.

Watch for signs such as:

unusual tiredness
irritability
excessive thirst
heavy sweating
weakness
dizziness
headache
nausea
becoming floppy or sleepy

Move the child somewhere cool and begin cooling them.

If they are alert and able to drink normally, give cool fluids.

Seek medical advice if you are concerned.

Call 999 if they develop signs suggesting heatstroke, such as confusion, seizures, reduced responsiveness or loss of consciousness.

Parents, carers and people working with children can learn how to recognise and manage childhood emergencies through practical Paediatric First Aid training.

Heat Illness in the Workplace

Heat illness is not restricted to heatwaves.

Workplaces can expose employees to significant heat through:

outdoor work
kitchens
factories
foundries
confined spaces
heavy physical activity
protective clothing
machinery and industrial processes

Employers should consider heat as part of their workplace risk assessment where relevant.

Controls may include:

access to drinking water
regular breaks
shaded or cooler rest areas
suitable clothing
adapting workloads
reducing strenuous work during extreme heat
allowing workers to acclimatise
recognising early signs of heat illness
having suitable emergency arrangements

First aid arrangements should reflect the actual hazards employees face.

Our guide explaining the legal requirement for first aid at work looks at employers’ wider responsibilities for workplace first aid provision.

Heat Illness During Sport and Exercise

Sport and strenuous exercise can significantly increase body temperature.

Risk can increase with:

intense exercise
endurance events
inadequate hydration
heavy clothing
lack of acclimatisation
hot or humid conditions

Coaches, event organisers and people responsible for physical training should understand the warning signs of exertional heatstroke.

A participant who becomes confused, uncoordinated, agitated or collapses should not simply be told to sit down and drink water.

Suspected heatstroke requires urgent assessment, a 999 call and immediate cooling.

Heat Exhaustion and Heatstroke Guide. Symptoms and First Aid

How Can Heat Exhaustion and Heatstroke Be Prevented?

Risk can be reduced by:

drinking enough fluids
taking regular breaks
using shade
wearing suitable loose clothing
avoiding unnecessary strenuous activity during extreme heat
gradually becoming accustomed to hot conditions
planning strenuous activities carefully
checking on vulnerable people
never leaving babies, children or vulnerable adults in parked vehicles

Workplaces and organised sporting activities should plan for heat-related emergencies where heat illness is a foreseeable risk.

Heat Exhaustion and Heatstroke: What to Remember

The key difference between heat exhaustion and heatstroke is the seriousness of the casualty’s condition.

HEAT EXHAUSTION

Move them somewhere cool.

Remove excess clothing.

Give cool fluids if they can drink safely.

Cool their skin.

Stay with them.

They should begin improving within approximately 30 minutes.

HEATSTROKE

Look particularly for confusion, agitation, disorientation, seizures or reduced consciousness.

Call 999 immediately.

Remove excess clothing.

Start rapid active cooling.

Use cold-water immersion where appropriate and safely available, or use the best effective cooling method available.

Do not delay cooling while waiting for the ambulance.

Monitor responsiveness and breathing.

Be prepared to start CPR if they become unresponsive and stop breathing normally.

The Resuscitation Council UK First Aid Guidelines provide current UK guidance on recognising and cooling heatstroke.

The NHS also provides public guidance on recognising heat exhaustion and heatstroke and when emergency help is required.

Learn How to Respond to Medical Emergencies

Knowing the difference between heat exhaustion and heatstroke is one part of being prepared for an emergency.

Practical first aid training teaches you how to assess a casualty, recognise when someone is becoming seriously unwell and take appropriate action while professional help is on its way.

First Aid and Safety Training provides:

We provide practical first aid training for individuals and organisations across the North East.

Explore our first aid training across the North East or contact First Aid and Safety Training to discuss your requirements.

You can also see our South Shields training centre and customer reviews on Google Maps.

Real Skills, Real Confidence.