Heat stress occurs when we produce more body heat than normal.
Jim Cotter, a professor at the University of Otago school of physical education, says “we’re physiologically designed to deal with heat better than any other species”.
“When we produce more, or it’s difficult to get rid of it, or we get a bit added to us from the environment, then that’s heat stress.”
The easiest way to avoid heat stress is to avoid hard physical work, heavy clothing and intense exercise on a hot day, Cotter says.
“They key point is what you’re doing and what you’re wearing. So if you’re generating a lot of heat and you can’t get rid of it, because the environment’s become warmer, that’s by far the biggest problem.
“Don’t do heavy work or wear heavy clothing on a hot day, don’t go and exercise hard.”
Heat exhaustion, on the other hand, causes symptoms including dizziness, nausea and muscle cramps due to overheating. It can generally be treated by moving into the shade, resting, hydrating and cooling yourself down.
Heat stroke is a medical emergency where “the rise in body temperature results in disruption to a number of bodily functions”, Eggleton says.
“People can become disorientated, have a fast heart rate, faster breathing and get dehydrated. Eventually body organs start to fail.”
The effects of heat stroke tend to be worse in older people and in those with chronic illnesses, while some medications can also make it harder for people to handle high temperatures.
The signs and symptoms include facial flushing, dizziness, nausea, headaches, weakness, tiredness and feeling “foggy”.
To treat someone with heat stroke, remove them from direct sunlight or heat to a cool environment, and help them rehydrate and cool down, Eggleton says. You can also apply ice packs to their head and neck.
Staying hydrated can help guard against heat stress and exhaustion. Photo / 123rf
“A fan by itself or air conditioning might not be effective enough. People should consider spraying cold water on the affected person with a fan directed at them,” Eggleton says.
“Treating heat stroke really depends on people being able to recognise it in others, as people experiencing heat stroke might become confused or may not recognise the symptoms in themselves.”
To avoid heat stroke, stay out of the sun during the hotter parts of the day, particularly around midday. Use sunscreen to guard against sun damage, though it won’t protect you from heat stroke, and avoid exercising when it’s hot.
Wearing a broad-brimmed hat and light, loose clothing, and drinking plenty of water can also help.
“Most importantly, be aware of neighbours and whānau who are elderly or who have chronic illnesses and check in with them – they might not be aware that they are suffering from heat effects,” Eggleton says.
What UV exposure does to your body
New Zealand has high levels of UV (ultraviolet) radiation from the sun, compared with other countries, and it tends to be higher during summer.
Dr Bronwen McNoe, senior research fellow at Otago University and co-lead director of the university’s Cancer Society Research Collaboration, says UV levels don’t always rise when it’s hotter.
“You can get high UV even on cool or cloudy days, so it’s important to protect your skin no matter the temperature. The real risk is that when it’s warm, people tend to spend more time outdoors, which means they are more likely to be exposed to high UVR and increase their risk of skin cancer.”
As well as skin cancer, UV exposure can lead to sunburn, early skin ageing and eye damage.
“It harms the skin’s DNA, and the damage adds up over time, so the more you’re exposed, the higher the risk.”
Those with an increased risk of getting skin cancer include outdoor workers like farmers and builders, those with fair skin, many moles, or a personal or family history of skin cancer, she says.
“Older adults and anyone who’s had a lot of sun or hasn’t used much protection are also more likely to be diagnosed with a skin cancer.”
If you’re exercising or swimming outside, make sure you reapply your sunscreen throughout the day. Photo / Getty Images
If you’re on certain medications or have an immune condition, that can increase your risk.
It doesn’t take long for sun damage to occur.
“Even short periods in the sun without protection can cause skin damage, especially when UVR levels are high. The longer you’re exposed, the greater the risk, and all that damage adds up over your lifetime.
“Sunburn and skin changes can happen quickly, especially if you have fair skin. How quickly your skin gets damaged by the sun depends on the UVR level, which changes with location, time of day, and season, as well as your skin type and what you’re wearing. Apps like UVNZ can give you a personalised estimate based on these factors.”
The advice for guarding against UV damage is the same as for avoiding heat stress and heat stroke – stay in the shade, stay hydrated, and if you’re exercising or swimming in the heat, remember to reapply sunscreen as water and sweat can dissolve it.
“If you take off clothing to cool down, make sure you still protect your skin from the sun,” McNoe says.
“To protect your skin, wear long sleeves, a sun protective hat and sunglasses, [and] use sunscreen with at least SPF 30 – preferably 50.”
Bethany Reitsma is a lifestyle writer who has been with the NZ Herald since 2019. She specialises in all things health and wellbeing and is passionate about telling Kiwis’ real-life stories.