How your body reacts in hot weather – and when you must dial 999

WE have been waiting absolutely ages after what feels like the longest and wettest winter and spring but finally, finally the great British Summertime has arrived.

And almost instantly, it is too hot!

The Met Office and UK Health Security Agency (UKHSA) have issued a yellow heat health alert for most of England for the next few days as temperatures are expected to hit approximately 31C.

A yellow alert is issued when temperatures reach a level which would mainly impact vulnerable people, for example those over the age of 65 or those with chronic health conditions.

Due to this, there may be impacts in the health and social care sectors.

Whatever the temperature outside – be it minus five or 35C – the body needs to stay in a very tightly controlled temperature range, between about 35-37.5 degrees. 

Think how unwell you feel when you have a fever which is not much higher!

This thermoregulatory control is called homeostasis and the body has mechansisms to try and keep itself at the correct temperature.

We shiver when we are cold and when we are too hot we become thirsty, encouraging us to drink. 

We also sweat to try to lose heat and the blood vessels in the skin dilate and widen in order to radiate out heat.

But if the body’s temperature control mechanisms become overwhelmed you may become more seriously unwell.

What are the health risks of a heatwave?

Heat exhaustion and heat stroke are health conditions related to the hot weather, but they don’t just occur outside. If your home is too hot they can occur inside as well. 

They are more likely to occur in older adults as well as babies and toddlers and those with chronic health conditions such as diabetes.

If you have a bowel condition which causes diarrhoea, such as Crohn’s disease, you may be more vulnerable, or if you are someone who is very physically active in the heat.

And remember that babies or people who are more unwell may not even be able to tell you what they are feeling.

Heat exhaustion vs. heat stroke

In heat exhaustion, the body is working hard to cool down.

Your body temperature might rise to around 38 degrees C and symptoms include feeling very sweaty, thirsty and feeling tired or dizzy.

You may notice that you don’t feel hungry, or feel nauseous and may have abdominal pain or even cramping in your limbs.

If you go to the toilet, the urine may be dark and concentrated, and you might not be producing very much.

If you notice these symptoms in yourself or someone else, take them inside, out of the sun, preferably into a cooler area.

You can use a fan to cool the room, take off clothes and drink cool fluids, if you feel sick drink a little at a time.  You can even use a cool flannel to sponge down to try to cool down.  

Hopefully you will feel better quickly, generally within about half an hour.

But if you don’t feel better after 30 minutes or if you worsen, your heat exhaustion may have progressed into heat stroke, which is a medical emergency.

In heat stroke, the body’s systems which it uses to try to keep you cool have become overwhelmed and stop working. Your temperature may rise to over 40C.

Symptoms include a headache, nausea and vomiting – which makes you lose even more fluid – very rapid breathing and pulse rate.

In heat exhaustion there is lots of sweating, but in heatstroke sweating stops.

You may also notice other symptoms like confusion, irritability and agitation and if left untreated there can be seizures and loss of consciousness.

Heatstroke can be – and is – fatal.

How to avoid heat stroke and heat exhaustion

Heatstroke and heat exhaustion are more likely outside in the sun but can also happen outside of direct sunlight in a hot room. 

Try to keep your home cool,  but remember this doesn’t necessarily mean opening the windows!

If it is hotter indoors than out, for example at night, open windows to let the cool air in, but, if it is hotter outdoors than in, keep them shut and close curtains to try to keep the heat out.

Wear loose clothing, preferably of natural fibres and hat and stay out of the sun when it is at its hottest, between 11am and 3pm and make sure that you are drinking plenty.  

Keep drinking, though preferably not alcohol! Even though drinks like coffee and tea contain caffeine, which is a diuretic and can make you urinate more, the volume you drink is likely to compensate for this.

Cool drinks are often more palatable in the hotter weather and don’t forget that ice lollies and fruit like watermelon can help you keep up your fluid intake.

And while it won’t stop you getting heatstroke, don’t forget the sunscreen to protect your skin in the sun.

Look for a high SPF sun cream, between SPF 30 and 50, with a high star rating to protect against both UVA and UVB rays.  Apply generously and reapply regularly.