Heatstroke: recognising it, emergency first aid and prevention

Heatstroke occurs when the body's temperature rises so high that its cooling mechanisms fail. It is the most serious end of a spectrum of heat-related illness that starts with dehydration and heat exhaustion. Left untreated it can damage the brain and other organs, which is why the NHS treats it as an emergency.

It can affect anyone in very hot conditions, but it is also a risk during hard physical activity in warmer weather. The NHS notes a high risk of heat exhaustion or heatstroke during hot weather or exercise.

Because confusion is one of the signs, the person affected may not recognise that something is wrong. Bystanders, colleagues and family often need to spot it and act.

The NHS lists the symptoms of heat exhaustion as tiredness, dizziness, headache, feeling or being sick, excessive sweating with pale, clammy skin, cramps in the arms, legs and stomach, a high temperature, being very thirsty and feeling irritable. The symptoms are often the same in adults and children. Someone with heat exhaustion needs to be cooled down and given fluids.

Heatstroke is different in kind. The NHS describes a very high temperature, hot skin without sweating, fast breathing and a fast heartbeat, confusion and restlessness, seizures (fits) and loss of consciousness. The change from sweating and clammy skin to hot, dry skin, together with confusion, is a key warning.

For heat exhaustion, the NHS gives four steps: move the person to a cool place; remove unnecessary clothing such as a jacket or socks; give plenty of water, and possibly an isotonic sports drink or oral rehydration powder to replace salt lost through sweating; and cool the skin by spraying or sponging with cool water and fanning. Cold packs wrapped in a cloth and placed under the armpits or on the neck help too. Stay with them until they are better, which should be within 30 minutes.

Get help from NHS 111 if heat exhaustion is hard to treat or you need advice. The NHS says to call 999 if there are signs of heatstroke, including being still unwell after 30 minutes of resting in a cool place, being cooled and drinking fluids, a very high temperature, hot skin that is not sweating, a fast heartbeat, fast breathing, confusion and lack of coordination, a seizure or loss of consciousness.

While waiting for help, the NHS advises wrapping the person in a cool, wet sheet, or fanning or sponging them down with cold water. If they lose consciousness, put them in the recovery position and tell the ambulance service, check breathing and pulse and carry out CPR if there is no sign of life.

The NHS heatwave guidance says anyone can be affected, but some people are more vulnerable. They include older people, especially those aged 65 and over, babies and children aged 5 years and under, and people who are pregnant or have serious long-term conditions such as heart problems, breathing problems, dementia, diabetes, kidney disease, Parkinson's disease, mobility problems, mental health problems, or drug or alcohol addiction.

It also names people who live alone and may be unable to care for themselves, people on multiple medicines or medicines that may make them more likely to be badly affected by hot weather, people already ill and dehydrated from diarrhoea and vomiting, and people who are homeless or who work or spend a lot of time outside, particularly if physically active, such as runners, cyclists and walkers, or whose jobs involve manual labour.

The NHS recommends several practical steps in hot weather, which also help prevent dehydration and let the body keep itself cool.

• Drink more cold drinks, especially if active or exercising, and avoid too much alcohol.

• Wear light-coloured, loose clothing.

• Avoid the sun between 11am and 3pm and avoid extreme exercise.

• Indoors on a very hot day, close curtains, and close windows if it is hotter outside than inside; turn off electrical equipment and lights that get hot.

• Check on children, older people and people with long-term conditions such as diabetes or heart problems.

• Electric fans can help if the temperature is below 35 degrees, according to the NHS heatwave page.

The NHS pages focus on recognising and acting on the emergency, and they do not set out what happens in hospital or how long recovery takes. Recovery varies from person to person, so follow the advice of the treating team.

If heatstroke happened at work or during sport, ask the team treating you or your GP when it is safe to return to heat or exertion, and think about what could be changed to reduce the chance of it happening again, using the prevention steps above.

Heatstroke is an emergency that is managed through 999 and NHS emergency departments; private services are not an alternative in the first hours. NHS 111 can advise on heat exhaustion that you are struggling to treat.

For prevention, local councils can inspect rented homes for hazards including excess heat, according to the NHS heatwave guidance, and GOV.UK provides heat advice. Employers also have a role in protecting staff who work in hot conditions.