What Happens If... Your Body Experiences Extreme Heat?

That lethargy you feel is not just in your head.
Your body can really struggle in extreme heat.
Kondo Photography via Getty Images
Your body can really struggle in extreme heat.

With heatwaves becoming a common occurence across the world, it’s important to understand just what extreme heat can do to your body – and why it’s something you need to monitor seriously.

While you’ll probably be aware of the risks, like sunburn and dehydration, you might not know that the way your body sweats, your levels of fatigue and your vital organs are all impacted, too.

Here’s what you need to know.

What happens to your skin?

The sun’s ultraviolet rays (UV) can cause the skin to burn when exposed for too long, which increases the risk of skin cancer, because it damages skin cell DNA, according to the Australian organisation, Cancer Council.

Sunburn also affects your body’s ability to cool itself and causes a loss of body fluids, as well as pain and damage to the skin.

Away from UV rays, the heat can lead to the development of heat rash, or prickly heat, too.

That’s skin irritation caused by excessive sweating which can occur at any age. It looks like a red cluster of pimples or blisters, and can occur on the neck, upper chest, groin, under the breasts and in elbow creases.

As the NHS explains: “Heat rash is uncomfortable, but usually harmless. It usually gets better on its own after a few days.”

What happens to your sweat?

When the brain senses your body is getting too hot, your blood vessels near your skin dilate, so you can lose heat at your skin’s surface.

But if the air outside of your body gets hotter than inside your body, the body’s sweat glands activate.

Sweat helps to reduce your body temperature when it’s too hot, keeping it at a balmy 37C by evaporating. This creates a cooling effect, and takes some of your body’s heat with it (so, while it might not be visually appealing, don’t wipe your sweat away!).

However, if humidity levels are high, your sweat will not evaporate quickly enough, so the body will find it much harder to release heat.

US’s Centres for Disease Control and Prevention (CDC) pointed out that other conditions can limit the ability to regulate temperature, too, such as old age, youth, obesity, fever, dehydration, heart disease, mental illness, poor circulation, sunburn, prescription drug use and alcohol.

According to The Guardian, you can sweat up to 10 litres a day. So, even if your body is working properly, you can get dehydrated easily if you don’t drink enough to replace those fluids.

If you can’t sweat properly across your whole body, you can overheat and develop heatstroke.

What happens to your brain?

You might think that the sun’s mighty impacts stop at the skin and at sweating – but you’d be wrong.

High temperatures have been connected to reduced cognitive function, errors of judgement, and increased risk of occupational injury.

There’s even a risk that the blood-brain barrier could break down at extremely high temperatures, meaning proteins and ions can accumulate in the brain, causing inflammation, according to a science reporter in The Guardian.

What happens to your heart?

If it’s too hot, the part of the brain that controls vital processes tells the heart to send more blood around the body.

That’s because your body tries to reroute blood flow to get more blood to your skin and release more heat.

But it means blood pressure is lower, so the heart workers faster – which can lead to dizziness and sickness.

Texas-based company Tenet Healthcare warns that the heat forces your heart to pump harder – and it may circulate two to four times as much blood per minute as it would in cooler temperatures.

In extreme circumstances, your body could end up being deprived of normal blood flow, leaking blood vessels and causing blood to coagulate. If blood pressure drops too far, the risk of a heart attacks increases as the heart becomes fatigued.

It can therefore be particularly dangerous to people with heart conditions, so if that’s you, you really need to keep your water uptake up in the heat.

It's important to look after yourself, as the heat affects you in more ways than you might realise.
ljubaphoto via Getty Images
It's important to look after yourself, as the heat affects you in more ways than you might realise.

What happens to your lungs?

Hot weather is usually accompanied by still air, where pollutants can stagnate, according to The Guardian.

Ground-level ozone is a harmful gas where pollutants emitted by cars, power plants and industrial sources react chemically to sunlight, and reduce lung function and can increase the risk of asthma morbidity and mortality.

The British Medical Journal published a report in 2020 that found “more than 6,000 deaths each year would have been avoided in the selected cities if countries had implemented stricter air quality standards.”

What happens to your muscles?

Heat cramps can occur usually in the abdomen, arms or legs, during strenuous activity in high temperatures, according to the US-based hospital, the Mayo Clinic.

That’s because sweating makes you more vulnerable to heat cramps – which deplete the body’s salt and moisture.

This can also be a symptom of heat exhaustion. If you have heart problems or are on a low-sodium diet and experience heat cramps, you should seek medical attention.

Can you become fatigued?

Hyperthermia is what happens when the body reaches a very high temperature, and it’s not able to regulate the body’s functions.

That can be as much as a one degree up to 38C, when heat exhaustion sets in – dizziness, visual disturbance, thirst, nausea, palpitations and numbness. Your skin can be cool and moist, pulse rate can be fast and weak, breathing can be fast and shallow, according to The Guardian.

This can worsen to heatstroke at 40C, which is a medical emergency – untreated, it can cause seizures, coma and death.

Symptoms include red, hot and dry skin (no sweat), rapid, strong pulse, throbbing headache, dizziness, nausea, confusion and unconsciousness.

Who is most vulnerable during periods of extreme heat?

Infants and children up to four years of age, people aged 65 and older, those who are overweight and those who are ill or on certain medications are at higher risk of heat-related illness, according to the CDC.

How can you look after yourself when it’s hot?

  • Drink cool, nonalcoholic beverages even if you don’t feel thirsty
  • Wear as little clothing as possible – lightweight, light-coloured, loose-fitting preferably with a hat to keep your heat cool
  • Apply suncream 30 minutes before going out, and continue to reapply according to the package directions
  • Stop all activity and sit in a cool place
  • If you have to work, pace yourself.

If you or someone around you starts to experience heat exhaustion, the NHS advises move them to a cool location, remove unnecessary layers like a jacket or socks, drink a sports or rehydration drink or cool water.

Cool their skin with a spray or sponge and fan them. Use cold packs wrapped in a cloth for under the armpit or on the neck. If they are still feeling unwell after 30 minutes of rest, the NHS recommends calling 111.

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