When the sun is out, many of us reach for sunscreen, but myths and misinformation have left some people confused about when and how to use it, and how to ensure we still get enough vitamin D. , a skin cancer expert at QIMR Berghofer Medical Research Institute in Australia, has led clinical trials looking at the link between sun exposure and skin cancer, and sunscreen use and vitamin D. She also recently led the development of a new that considers how to balance the risks and benefits of sun exposure. Here, she lists five things that everyone should know about sunscreen.

Sunscreen should be used as a last line of defence

Many people think it鈥檚 OK to lie on the beach all day in a tiny bikini as long as they rub sunscreen all over their exposed skin and reapply it every 2 hours. They think sunscreen makes them bulletproof. But even if you apply the best sunscreen perfectly, it still lets some ultraviolet (UV) radiation through. If you鈥檙e out in the sun for hours, that gradually adds up to a dose that is big enough to cause skin damage. At that point, it doesn鈥檛 matter if you apply more sunscreen; the damage is already done.

People often assume that if they reapply sunscreen every 2 hours, they鈥檙e sort of starting the protection again, but that鈥檚 not how it works. You also need to protect yourself with a hat, sunglasses, rash shirt or other protective clothing, and stay in the shade in the middle of the day. Sunscreen should be considered a last line of defence for the parts of your skin that you can鈥檛 easily cover while you鈥檙e outdoors, like your hands and neck.

There is good evidence that sunscreen protects against skin cancer and wrinkles

The largest, longest-running study of sunscreen was conducted in the Australian town of Nambour. In 1992, 1600 people in the town were randomised to apply daily sunscreen or continue with their normal sunscreen use, which tended to be minimal. It found that those who applied the daily sunscreen were years down the track.

The researchers also created moulds of the backs of the study participants鈥� hands to look at damage to the surface of the skin. Those in the daily sunscreen group had compared with those who didn鈥檛. When they were followed up on in 2014, they also had .

The sunscreen to choose is the one you like wearing

It鈥檚 no good having sunscreen that sits in your cupboard and doesn鈥檛 end up on your skin because you don鈥檛 like the feel of it. If you鈥檙e going on a hike and you鈥檙e going to be out all day, it鈥檚 better to wear sunscreen with a high sun protection factor (SPF) of 50+. But it鈥檚 harder to get a high-SPF sunscreen that feels really nice, so if you鈥檒l be popping out for only short periods throughout the day, you can choose an SPF 15 or 30 sunscreen. Tinted sunscreens can offer the same protection as normal sunscreens, but only if you apply them thickly. But because these often make the skin look overly tinted, people tend to apply them too thinly. One option is to first put on a thick layer of normal sunscreen, then apply the tinted sunscreen on top of it.

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Chemical sunscreens, meaning those that contain organic ingredients such as octocrylene and avobenzone, work by absorbing UV radiation from the sun and converting it to harmless heat. Inorganic sunscreens, also known as mineral or physical sunscreens, contain zinc oxide or titanium dioxide particles. They are often reported to work by reflecting or scattering UV radiation, but they actually , like chemical sunscreens.

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Wearing two layers of sunscreen helps to achieve adequate coverage

You get the SPF listed on the bottle only if you apply 2 milligrams of sunscreen per square centimetre of skin, which is around in an average adult. But it鈥檚 really hard to apply this amount of sunscreen in one go. One day, I decided to measure it out exactly, and I couldn鈥檛 rub it all on; it was too much. So now, I apply one layer, let it sink in while I brush my teeth and do other things, and then a second layer, so I can apply the full recommended amount.

I was born in Armidale, Australia, in the late 1960s and didn鈥檛 wear sunscreen as a child, despite my pale skin. I鈥檝e since had three skin cancers removed, the first of which appeared when I was just 29. So now, I am careful to protect my skin.

If you鈥檙e diligent with sunscreen, you might need to take a vitamin D supplement

We recently conducted a trial called the Sun-D Study to see whether applying SPF 50+ sunscreen every day affects people鈥檚 vitamin D levels. We randomly assigned 639 people to apply SPF 50+ sunscreen as part of their daily morning routine on days when the UV index was forecast to reach 3 or higher, or to use it at their own discretion. After about a year, a 鈥� about 46 per cent compared with 37 per cent in the control group. If you wear sunscreen every day, I would advise taking a vitamin D supplement so that you don鈥檛 become deficient, especially in winter. I take one myself 鈥� they are cheap, safe and effective.

People with dark-coloured skin are at greater risk of developing a vitamin D deficiency. I recently led the development of a new that looked at how to balance the various risks and benefits of sun exposure. It brought together experts from many Australian universities and medical organisations, and it concluded that people with dark-coloured skin need to put on sunscreen only if they plan to spend more than 2 hours outdoors on days with high UV radiation levels. This is in recognition of the fact that melanoma incidence is 30 times lower in people with dark-coloured skin than in those with light-coloured skin, and that vitamin D deficiency poses a greater risk.

This week鈥檚 heatwave is the hottest ever recorded in Europe, as well as the most humid, and it is likely to cause thousands of deaths.

Although a potential 鈥渟uper El Ni帽o鈥� is forming in the Pacific Ocean, this didn鈥檛 play a role in the heatwave, a study by the World Weather Attribution network of scientists has found. Instead, global warming is clearly to blame.

The study analysed how likely the average daily maximum temperature projected for 26 to 28 June in western and central Europe would have been in the cooler climates of 1976 and of 2003.

While the weather pattern 鈥� a low-pressure heat dome that is trapping hot air from the south 鈥� isn鈥檛 unusual, the temperatures are. Fifty years ago, a typical June heatwave would have been about 3.5掳C cooler, and the temperatures seen over the next three days would have been a less-than-one-in-10,000-year occurrence.

Daytime temperatures have 44掳C聽 (111掳F) in one French town, and nighttime temperatures have remained above 30掳C (86掳F) in parts of Spain.

鈥淭his event would not have been possible in June without climate change,鈥� at Imperial College London said at a media briefing on 25 June. 鈥淭he three-day nighttime temperatures would not have been possible at any time of year without climate change.鈥�

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The humidity has also been unprecedented, reaching more than 50 per cent in many British cities. Dew-point temperatures have been in the low 20s, as compared to the single digits during the July 2022 heatwave that set the UK鈥檚 temperature record.

The wet-bulb globe temperature, which measures not just air temperature but also humidity, heat radiation and air movement, has broken or is expected to break records in almost half of European cities, the study found.

Humidity amplifies health risks because it slows evaporation, making sweating less effective. While older people or those who have a chronic illness are in particular danger, so are migrants and people experiencing homelessness.

鈥淲hat we see very clearly鈥� is how unequal the effects of this heatwave are and how that really demonstrates the inequality that widens due to climate change,鈥� said , also at Imperial College London. 鈥淏ecause it鈥檚 of course people who are particularly vulnerable who are most likely to lose their lives.鈥�

While it is too soon to look at excess mortality, a previous study found a smaller heatwave in June and July 2025 killed 2300 people in London and 11 other European cities.

鈥淭he health impacts of this heatwave are likely to be extremely high across large parts of northern and central Europe,鈥� said Keeping.

Heatwaves will become even more intense and frequent unless we rapidly cut fossil fuel emissions, the researchers stressed. And Europe, the fastest warming continent, is not ready, as it has an ageing, urban population living in cities built for a cooler era. In the UK, only 5 per cent of homes have air conditioning.

Besides AC, Europe should invest in passive cooling like building insulation, ventilation, green roofs and walls and trees along streets, they said. It should also expand its heat response to include oft-forgotten groups like people with mental health conditions and those who are pregnant, said Carolina Pereira Marghidan at the Red Cross Red Crescent Climate Centre.

鈥淓urope has heat action plans, but research has also shown that sometimes they do not cover all the groups that may be vulnerable,鈥� she said.

Europe suffered unprecedented wildfires and heatwaves in 2025, impacts that are expected to worsen on the world鈥檚 fastest-warming continent.

Last year was the hottest year on record in the UK, Iceland and Norway and one of the three hottest years in Europe as a whole, according to an annual report by the European Centre for Medium-Range Weather Forecasts (ECMWF). More than 95 per cent of the continent experienced above-average annual temperatures. Scandinavia, Finland and north-western Russia saw their worst-ever heatwave, 21 days of simmering temperatures that reached 30掳C (86掳F) even at the Arctic circle.

This extreme heat probably stunted animal and plant growth while encouraging the spread of invasive species and pests, showing how the climate crisis is contributing to a crash in biodiversity, at the World Meteorological Organization said at a press conference.

鈥淭his region would [typically] see zero to two days of strong heat stress, and we are speaking about 21, so this had a major impact on ecosystem health,鈥� she said. 鈥淪ince 1980, Europe has been warming twice as fast as the global average, [and] heatwaves are becoming more frequent and severe.鈥�

Climate warming set the stage for record wildfires in Portugal and Spain in August, the extremely hot, dry, windy conditions there at least 40 times more likely. More than 10,000 square kilometres burned, and at least three people were killed. Fires approached Madrid, and authorities had to shut down parts of the Camino de Santiago pilgrimage route. Smoke drifted as far as the UK.

Across Europe, wildfires emitted 47 million tonnes of carbon, a record amount. Spain, the UK, the Netherlands, Germany and Cyprus all topped their previous fire-emissions records.

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Soil conditions were the driest in 33 years of observations, with more than a third of Europe suffering extreme agricultural drought, especially the UK, Turkey and Ukraine. While parched soils probably encouraged wildfires in many countries, it was increasing fluctuations in the weather that supercharged the blazes in Portugal and Spain, according to at ECMWF. An extremely wet spring that boosted vegetation growth was followed by record summer heat, which dried out those plants and shrubs, creating a tinderbox.

鈥淚f you have a very high fuel load in addition to the wildfire weather, so hot, dry winds in particular, that鈥檚 when we get these catastrophic conditions where wildfires spread very quickly,鈥� Burgess said at the briefing. 鈥淣ational parks need鈥� firebreaks around them to make sure if there is a fire, it doesn鈥檛 spread.鈥�

The ocean around Europe was also abnormally hot, breaking the record for annual sea surface temperature for the fourth year in a row. A record 86 per cent of these seas suffered strong, severe or extreme marine heatwaves. The most extreme hotspots occurred west of Ireland, south of Iceland and south-east of Spain.

For the past three years, heatwaves have struck 100 per cent of the Mediterranean Sea, which is warming up faster than the global average. Waters in Italy and Spain reached 30掳C, warmer than a typical swimming pool, raising the risk of fish death, as well as the spread of bacteria and algae. Past marine heatwaves in the Mediterranean have killed off huge amounts of coral, seagrass beds and shellfish.

To limit future damage, Europe needs to lead the way on slowing climate change, of the European Commission said at the briefing. In 2025, solar power generated a record 12.5 per cent of the continent鈥檚 electricity, with a total 46 per cent coming from renewables.

European countries are also among those taking part in the first in Colombia this week, which was organised after the COP30 climate summit in Brazil failed to agree on a roadmap to end oil, gas and coal emissions.

At the same time, Europe should adapt to future climate risks, such as multi-year megadroughts similar to the one already gripping the western US, according to officials.

鈥淲e need to address these risks,鈥� Chrenek said. 鈥淭he cost of inaction is significantly higher than the cost of tackling negative impacts.鈥�

Sweltering heatwaves can have lasting health impacts 鈥� accumulated exposure to hot-weather days appears to accelerate people鈥檚 biological ageing.

鈥淲e now have at least two prominent studies showing an impact of heatwave exposure on ageing, with these examining populations from two different countries,鈥� says at Macquarie University in Australia. 鈥淲e all need to take heatwaves seriously 鈥� not only looking after our own health but also that of others in our communities.鈥�

The newest research comes from at The University of Hong Kong and her colleagues. First, the researchers used medical screening data from nearly 25,000 adults in Taiwan to determine the biological age of each person based on factors such as inflammation, blood pressure and organ functions. Next, they compared each individual鈥檚 biological age with their chronological age, to figure out if they were ageing faster or slower than normal.

鈥淭he physiological changes in the body associated with ageing can appear earlier and progress faster in some people than in others,鈥� says Beggs, who was not involved in the research.

The team then calculated each person鈥檚 cumulative exposure to heatwaves 鈥� including the total number of heatwaves they lived through and the sum of temperatures across these periods 鈥� two years prior to their medical screening. The total number of heatwave days experienced ended up being the most significant factor for accelerated ageing in this Taiwanese population. The results aligned with another that investigated outdoor heat鈥檚 impact on ageing in older US adults.

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For the Taiwanese group, the ageing effect generally increased as the amount of cumulative heatwave exposure did. Each four-day increase in total heatwave duration was associated with a biological age increase equivalent to about nine days.

But the effect was even more pronounced for specific groups of people. For instance, manual workers experienced around three times as much accelerated ageing from the same amount of heat exposure compared to the group as a whole. Residents of rural communities also experienced greater ageing impacts, indicating access to air conditioners might be able to stave off heat鈥檚 ageing effects, the researchers say.

To avoid making climate change and heatwaves worse, however, the protective benefits of air conditioning will need to be complemented by more sustainable cooling solutions, says Beggs. 鈥淎ir conditioners also directly add to the heat outdoors, making conditions for those without air conditioners even worse than they would have been,鈥� he says.