Heatstroke and heat exhaustion

We’ve had some extraordinary weather in the UK in recent years, regularly approaching or beating the record for the hottest day ever. Of course, most of us love a balmy summer evening and relish the opportunity to shed the multiple layers required most of the time for life in the UK.

But there are both short-term and long-term risks associated with too much sun.

Staying Safe in the Sun

Staying safe in the sun should always be a top priority. This means regularly reapplying sunscreen, staying well-hydrated, and avoiding the midday sun whenever possible. These simple steps can go a long way in protecting your health.

READ MORE: How to Stay Safe in the Sun

If you have a pre-existing medical condition such as asthma, COPD, or cardiovascular disease, it's essential to be mindful that prolonged exposure to heat can exacerbate your symptoms.

READ MORE: Which Medical Conditions Get Worse in the Hot Weather?

What is Heatstroke and Heat Exhaustion?

Heatstroke and heat exhaustion are two serious conditions caused by the body overheating, typically after prolonged exposure to high temperatures or physical exertion in hot weather. In the short term, heat exhaustion and its more dangerous relative heatstroke (sometimes called sunstroke) should always be on our minds.

In the early stages, your body will be working hard to keep your internal temperature and fluid/mineral levels constant. It will try to retain fluid by reabsorbing water from your kidneys, but you’ll also be sweating as this cools your body down.

Different causes may occur together: if your main problem is dehydration, symptoms can include (perhaps obviously) feeling extremely thirsty, along with headache and general weakness. But if your mineral balance has been disrupted, especially by excessive sweating, you may also experience muscle cramps, feeling or being sick, and light-headedness.

Recognising these conditions promptly is vital to protecting yourself and others during hot weather.

Heat Exhaustion Symptoms

Heat exhaustion is the less severe of the two conditions and can develop after spending long periods in the sun, especially without adequate hydration.

Early symptoms of heat exhaustion largely relate to dehydration, so you’re likely to be passing only small amounts of dark, concentrated urine as your body tries to retain fluid. You may also experience:

• Dizziness and feeling faint.
• Headache (often throbbing).
• Stomach cramps, nausea, vomiting and being off your food - sometimes accompanied by diarrhoea.
• Lack of energy.
• Muscle cramps in your arms and legs.
• Problems concentrating or confusion.
• Profuse sweating and pale skin.

Heatstroke Symptoms

Heatstroke occurs when the body loses its ability to regulate temperature. This means your body temperature can rise dangerously to above 40°C.

If heat exhaustion isn’t recognised and treated, it can progress to heatstroke. This is a medical emergency – your body is no longer capable of keeping your internal environment stable and, for instance, you’ll stop losing heat by sweating. In addition, you’re likely to experience:

• More severe dizziness or fainting.
• A greater degree of confusion or loss of consciousness.
• Severe, throbbing headache.
• Nausea and vomiting.
• Very hot, flushed skin.
• Worsening muscle cramps or weakness.
• A rapid pulse which can be very weak or unusually strong.

If untreated, heatstroke can lead to serious damage to your vital organs (including swelling of the brain) and can be fatal.

How Do I Treat Heat Exhaustion?

To treat heat exhaustion, the main goal is to cool down.

• The first step is to get out of the heat into a cool (preferably air-conditioned) place.
• Remove tight or restrictive clothing and if possible, take a cool/tepid bath or shower (not too cold as this can cause the blood vessels in the skin to contract, preventing sweating). If there’s no shower available, sponge yourself down with cool water or get someone to do it for you.
• When you get out of the shower, don’t dry off completely. Instead, put on a fan to increase sweat evaporation and skin cooling.
• Lie down and rest until you feel completely better and ideally stay in the cool for the rest of the day.
• Even when you've recovered, you'll likely be more sensitive to the heat for several days. Cancel any strenuous activities, stay out of the sun as much as possible, avoid alcohol and make sure you keep topped up with non-alcoholic fluids (you should be passing good amounts of pale straw-coloured urine regularly).

If you don’t feel better within half an hour or so – or if you develop any symptoms of heatstroke – seek urgent medical help.

How Do I Treat Heatstroke?

Heatstroke is a medical emergency. Someone with heatstroke is unlikely to be able to help themselves, so it’s up to you to take prompt action.

• First, call for emergency medical help. If you are not sure of the emergency services number, the Foreign and Commonwealth Office has a list of the emergency numbers for every country. Go to their website on travel advice, select the country you’re visiting and click on the 'Health' section.
• While you’re waiting for help to arrive, move them to a cool place. Remove as much clothing as possible and lie them down – in the recovery position if they’re very faint or have lost consciousness.
• Stay with them at all times – someone with heatstroke can have a seizure. If they’re capable, help them into a cool bath or shower – if not, moisten their skin with a wet towel, then apply a fan.

Remember, recognising the symptoms of heat-related illnesses early and acting promptly can make a critical difference. Always prioritise safety and seek professional medical attention when necessary to ensure the wellbeing of yourself and others.

Who’s at Risk?

Anyone can get heat stroke or heat exhaustion, but along with babies and toddlers, you’re at particular risk if you:

• Are older, especially if you’re frail.
• Do a lot of physical activity, leading to more sweating and increased body temperature.
• Take water tablets (commonly prescribed for high blood pressure or heart failure – your pharmacist can advise if you’re taking one).
• Take certain medications for mental health problems.
• Have underlying health issues such as kidney, lung or heart disease, diabetes, sickle cell disease or sickle cell trait.
• Are underweight or very overweight.
• Have gut problems, including ongoing issues such as Crohn’s disease and ulcerative colitis or short-term tummy bugs.

The same groups are at risk of both heatstroke and heat exhaustion. Heat stroke happens when your body is so overwhelmed by heat and its consequences that it can no longer control its internal temperature.

Fairly obviously, heat exhaustion is closely related to the outside temperature. However, very humid weather (particularly humidity over 60%) increases the risk because it hinders your ability to cool your core body temperature down by sweating. Likewise, if the air is very still (for instance in cities or built-up areas) the sweat won’t evaporate as effectively.

If you are at high risk of heat exhaustion or heat stroke, you may find that opting for a cooler holiday destination could be a safer and more enjoyable choice. Cooler climates can help reduce the strain on your body caused by extreme heat, allowing you to relax and explore without the constant worry of overheating.

READ MORE: Escape the Heat: Cooler Destinations for Summer Holidays

How Do I Avoid Heatstroke and Heat Exhaustion?

A combination of staying hydrated and keeping cool is key to avoiding heat exhaustion, especially if you’re at high risk.

Avoid Mid-Day Sunshine

The sun is strongest between 10 am and 4 pm. Limit your time outdoors during these hours, if possible.

Seek out shade whenever possible and be aware of the temperature inside your car or home. Ensure proper ventilation and use fans or air conditioning if necessary. Don’t forget that the sun can reflect off pale surfaces or water, so it’s possible to get overheated even in the shade.

Stay Hydrated

Drinking enough non-alcoholic fluids to stay hydrated and avoid feeling thirsty is essential for your overall health. Dehydration can often creep up on you, especially during hot weather or physical activity, so it’s important to stay ahead of it.

Always carry a bottle of water with you whenever you go outside, whether you're running errands, exercising, or just enjoying the day. Make it a habit to take very regular sips throughout the day, even if you don't feel thirsty yet, to ensure your body gets the hydration it needs to function at its best.

Avoid Exercise

Strenuous exercise, especially in the middle of the day when temperatures tend to be highest, should be avoided. If you are exercising, drink about a glass of water every 20 minutes, even if you don’t feel thirsty.

It may be worth considering a sports drink as part of your fluid intake, especially if you lose a lot of sweat – this can replace electrolytes lost in sweat.

Wear Suitable Clothing

Wear loose, floaty clothes in natural, breathable materials like cotton or linen. Light-coloured clothing is better than dark because the light colours will reflect sunlight instead of absorbing it.

Don’t forget to wear a wide-brimmed hat (especially if you’re a little short of head hair).

Bonus Tip: Keep your Suncream Topped Up

Wearing sunscreen won’t reduce your risk of heat exhaustion but it can greatly cut the chance of painful sunburn. Opt for a minimum of factor 15 if you have very dark skin; factor 30 for lighter skin; and factor 50 if you burn easily.

Being able to recognise the signs of heat exhaustion and its more serious counterpart, heat stroke, is essential, especially when spending time outdoors or on holiday. These conditions can escalate quickly, so knowing what to look for and how to act is vital.

Always remember to take regular breaks from the sun, stay hydrated, and find ways to cool down if you start feeling overheated. Prevention is key, but if you or a loved one show symptoms of heat stroke—such as confusion, dizziness, or loss of consciousness—seek emergency medical help immediately.

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