Heatstroke warning signs and how to cool down

Dr Lara Batchat - MBBS, BSc (hons), MRCGP, DCH, DRCOG
·8 min read
Photo credit: Dmitry Marchenko / EyeEm - Getty Images
Photo credit: Dmitry Marchenko / EyeEm - Getty Images

Soaking up the summer sun is one of life's great pleasures – but you can have too much of a good thing. Heat exhaustion is not usually serious, but if it develops into heatstroke this can have serious health consequences and needs to be treated as an emergency.

Family GP Dr Lara Batchat looks at heatstroke symptoms, causes, warning signs and how to keep your cool as the mercury rises:

What is heatstroke?

Heatstroke occurs when the body is exposed to too much heat and can no longer regulate its own temperature. The internal body temperature soars to over 400C and this can cause serious damage to the kidneys, brain and other vital organs if not treated quickly, so it is a medical emergency.

Heat exhaustion is the stage before heatstroke; it's important to be aware of the signs of heat exhaustion so that they can be dealt with promptly, to avoid progression to heatstroke.

Heatstroke causes

Like the finest symphony orchestra, your body is a sophisticated example of teamwork, with all the vital organs working closely together to keep things in balance. If exposed to too much of anything, your body has systems in place to compensate, and this is called homeostasis.

When it comes to heat, there are several mechanisms that can be put into place to keep a steady body temperature. Your skin sweats to lose heat by evaporation, your kidneys produce less urine to preserve fluid and maintain salt levels, thirst alarms are released to get more fluid in, and your brain sends signals to you to move away from the heat. However, if a person spends too much time in a hot environment, the body has to work much harder and may struggle to cope, resulting in heatstroke.

Photo credit: Westend61 - Getty Images
Photo credit: Westend61 - Getty Images

What are the first signs of heat exhaustion?

It’s important to be aware of the first signs of heat exhaustion so that you can take steps to help recover before heatstroke has a chance to set in. Heat exhaustion warning signs include the following:

  • Passing less urine, which might look darker in colour

  • Headache

  • Tiredness

  • Dizziness and feeling faint

  • Confusion

  • Feeling sick

  • Loss of appetite

  • Extreme thirst

  • Cramping in the arms, legs and tummy

  • Excessively sweaty, clammy skin

  • Looking pale

  • Fast pulse and breathing

  • Temperature of 380C or above

  • Children can seem floppy

How to treat heat exhaustion

If you notice any of the symptoms of heat exhaustion, it’s best to treat promptly. Follow these simple measures to cool someone down as quickly as possible:

1. Seek shade

Move to a cooler place as soon as possible – perhaps a shady area or indoor space.

2. Undress

Take off as much clothing as possible to lower your body temperature, especially tight-fitting clothes.

3. Rest

Lie down and put your feet up until you start to feel better.

4. Cool your skin

The safest way to cool down is by sponging down or spraying with cool water and using a fan. Resist the urge to jump into a freezing cold shower as the extreme temperature change could make you feel worse.

5. Rehydrate

Drink plenty of water or rehydration drinks; avoid alcohol or caffeine which can dehydrate you and exacerbate your symptoms.

6. Try cold packs

For young healthy adults who have been exercising vigorously, applying cold packs around the armpits and neck can be useful. Do not use cold packs in other cases of suspected heat exhaustion or heatstroke as this can be harmful.

7. Stay with a friend

If you are with a friend who you suspect might be suffering from heat exhaustion, stay with the person at all times until they start to feel better.

If a person still feels unwell after 30 minutes of resting in a cool place and drinking fluids, this may indicate heatstroke and so urgent medical attention should be sought.

Heatstroke symptoms

Heatstroke can be very dangerous if it isn’t dealt with quickly and in severe cases can be fatal – it’s safest to consider all cases as critical cases. Symptoms of heatstroke to look out for include the following:

  • Feeling very dizzy or fainting

  • Confusion and agitation

  • A severe, throbbing headache

  • Weak, cramping muscles

  • Feeling very sick and vomiting

  • Very hot flushed-looking skin

  • A temperature of 400C or above

  • A fast pulse (over 100 beats per minute) which might feel weak or strong

  • Shallow, fast breathing or shortness of breath

  • No sweating despite feeling hot

  • Collapse and losing consciousness

  • Seizures (fits)

If you suspect you or someone with you might be suffering from heatstroke, call 999 as soon as possible for urgent medical help and stay with the person at all times.

In the meantime, the same measures as for heat exhaustion should be taken if safely possible. If the person loses consciousness, you should put them in the recovery position until help arrives.

What's the difference between heatstroke and sunstroke?

Heatstroke can occur if there is any source of prolonged exposure to a hot environment. Sunstroke is one particular type of heatstroke, caused by exposure to too much sunlight.

The resulting symptoms and treatment are exactly the same, but with sunstroke, there may be the added issue of severe sunburn. It’s important to be aware of this if sponging the body with cool water, taking care to do so gently, to avoid worsening any blistered, sunburnt skin.

Heatstroke risk factors

The main risk factor for heatstroke is hot weather, especially a sudden heatwave, which doesn’t offer the body much opportunity to acclimatise. Humidity also affects the body’s ability to sweat and so it’s harder to keep cool. Other heatstroke risk factors include the following:

• Extremes of age

Young children and babies don't have fully developed nervous systems and so don’t have the mechanisms in place to regulate body temperature. Similarly, the elderly may have weakened nervous systems which can’t adapt in the same was as those of healthy young adults. Both groups may also find it harder to maintain good hydration. These factors, together, put both the very young and elderly at increased risk of heatstroke.

• Dehydration

Dehydration from not drinking enough fluids, or drinking the wrong ones (alcohol or excessive caffeine) can cause you to overheat.

• Overdressing

Wearing heavy, thick inappropriate clothing which doesn’t allow the body to release heat can put you at risk of heatstroke.

• Long term health conditions

Long term health conditions such as diabetes, heart, lung or kidney disease are heatstroke risk factors.

• Certain medications

Medication such as water tablets (often prescribed for heart conditions or raised blood pressure), antipsychotics (which can be given for various mental health conditions) and stimulants for attention-deficit/hyperactivity disorder (ADHD) can alter the body’s systems to regulate internal temperature and hydration.

• Diarrhoea

A simple tummy bug or conditions like Crohn’s Disease, colitis and diverticulitis can cause dehydration as a result of profuse diarrhoea, making it harder for the body to cool down in hot environments.

• Exercise

Prolonged exercise such as long distance running, especially when undertaken in hot weather, can put you at increased risk of heatstroke.

How long does it take to recover from heatstroke?

If treated promptly, most people will recover quickly from heatstroke but a hospital stay of around 1-2 days may be typical for rehydration and rehabilitation.

However, if there is delay in initial treatment, then damage to vital organs can cause complications and this may involve much lengthier recovery times of up to several months.

Those who have suffered with heatstroke may be prone to it again during hot weather and so should take care to avoid overheating.

Heatstroke prevention tips

During hot weather, follow these simple steps to avoid heat exhaustion and heatstroke:

✔️ Avoid the midday sun

Avoid being out in the sun during the hottest hours of the day, between 11am-3pm; if you want to exercise outdoors, do so in the early morning or late evening when it is cooler.

✔️ Practice sun safety

Use sunscreen (SPF 30 or more) and wear a wide brimmed hat to avoid sunburn, which reduces your body’s self-cooling mechanisms.

✔️ Wear natural fibres

Wear light coloured, loose fitting clothes made of natural fibres like cotton, to allow your skin to evaporate heat by sweating.

✔️ Keep hydrated

Drink lots of cold drinks to keep hydrated and if exercising, make sure to supplement your fluid intake accordingly. A good way to know if you are drinking enough, is by checking the colour of your urine and making sure it’s light coloured – as they say, “a happy mountaineer always pees clear!”

✔️ Stay cool

Cool down by taking a cold bath or shower, you could also use a damp flannel on the back of the neck or water sprinkled over your skin or clothes – the evaporating effect will help keep you feeling refreshed.

✔️ Practice car safety

Remember to never leave anyone in a parked car during warm or hot weather and keep your car locked when not in use, to avoid anyone inadvertently getting inside.

✔️ Avoid alcohol

Alcohol dehydrates and reduces your awareness of warning symptoms of heatstroke.

✔️ Keep your home cool

During a heatwave, shut the curtains during the daytime to avoid sunlight streaming in and if the temperature is hotter outside than in, keep the windows closed and use a fan. Open the windows at night when the outdoor temperature may be cooler.

Last updated: 23-04-2021

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