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’s 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’re 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’t matter if you apply more sunscreen; the damage is already done.

People often assume that if they reapply sunscreen every 2 hours, they’re sort of starting the protection again, but that’s 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’t easily cover while you’re 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’ hands to look at damage to the surface of the skin. Those in the daily sunscreen group had compared with those who didn’t. When they were followed up on in 2014, they also had .

The sunscreen to choose is the one you like wearing

It’s no good having sunscreen that sits in your cupboard and doesn’t end up on your skin because you don’t like the feel of it. If you’re going on a hike and you’re going to be out all day, it’s better to wear sunscreen with a high sun protection factor (SPF) of 50+. But it’s harder to get a high-SPF sunscreen that feels really nice, so if you’ll 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.

Free newsletter

Sign up to Eight Weeks to a ��ҹ����1000����ier You

Sign up to newsletter

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.

The only four skincare ingredients that have been proven to work

In the quest for better skin, we are faced with an overwhelming choice of creams and serums to enhance our appearance. Here's what works – and what doesn't

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’s really hard to apply this amount of sunscreen in one go. One day, I decided to measure it out exactly, and I couldn’t 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’t wear sunscreen as a child, despite my pale skin. I’ve 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’re 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’s 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 – 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’t become deficient, especially in winter. I take one myself – 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.

SpudCell represents a significant breakthrough in the creation of artificial life

The heatwave that swept Europe last week saw many temperature records broken, leading people to ask if extraordinary June heat is the “new normal”. Unfortunately, the truth is that we are never going to have normal in our lifetimes again – just ever more extreme heat.

Climate scientists are continually warning of the need to prepare for hotter heatwaves, worse droughts, more flooding and rising seas. During heatwaves like the one just passed, the hottest and most humid ever seen in Europe, they might even get a little media coverage. But then the weather cools, the news agenda moves on and nothing is ever done.

We are currently on course for average global surface temperatures to rise by between 2.1°C and 3.3°C by 2100, and possibly even more. Even these alarming numbers are a little misleading because the oceans that cover most of the planet don’t warm as fast as the land. Average land temperatures are therefore going to go up by a lot more than the above numbers imply.

But what really matters to us is extreme weather, not the average. The projections for future extremes are already dire, and there are reasons to think that we are in for extremes even greater than those currently projected for a given level of warming. With uncertainties over the survival of the vital AMOC ocean current and the risk of a major glacier collapse, the only thing we really do know is that we must prepare for conditions far worse than Europe has just experienced.

We are on course for average global surface temperatures to rise by between 2.1°C and 3.3°C

It is possible to get through even worse heatwaves if all your infrastructure and systems are geared up to cope, but for most countries, this isn’t the case. The fact is, the world is changing fast and we need to change just about every aspect of our lives to adapt – our homes and offices, factories and schools, cars and trains, farms and gardens, and so on. But it isn’t happening. One day, after the tragic deaths grow too great to bear, we will ask why we did nothing to prevent them.

Our brains love shortcuts. Decisions are often made via a subconscious muddling through, due to the . It is perhaps why we value neat categorisations of someone’s brain state, despite these being flawed.

Take the age at which you become an adult. Around the world, legal adulthood varies from 16 to 21. This difference matters, as we rightly have different expectations for children versus adults. Some call for this tension to be smoothed by asking policy-makers to consider typical brain maturity levels, ascertained via tools like brain imaging, in matters like criminal sentencing or the right to drive. The idea that our brains don’t fully develop until we are 25 is also becoming popular, but – as we discuss in our special on brain changes – this is wrong. Brains mature at different rates and there are myriad ways to measure their development.

This isn’t the only way neuroscience is looked to for informing policy before the science is ready. Take autism, which may come in several distinct types. A recently proposed category of “profound autism” could identify those with the highest needs, by assessing IQ, language skills and care requirements. This could assist in advocating for services for people in this group, but may exclude those who don’t meet strict criteria. It could also people with speech difficulties with people with cognitive impairments – different neurological profiles demanding different help.

Neuroscience is looked to for informing policy before the science is ready

Attempts to use psychological profiling in courts, too, are worrying. When presented as a mitigating factor in some cases, , taking a slam-dunk prosecution down a messier road. But . shows that, while potentially legally relevant, it can’t be used with confidence.

Our wish to put brains into tidy boxes is natural, and a future in which neuroscience can help us put a fine point on someone’s cognitive state could well be possible. That future, though, is not yet here.