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.

A first-of-its-kind cream that targets the underlying cause of vitiligo will be made available on the National 91色情片 Service in England. In clinical trials, the cream significantly increased pigmentation in the white skin patches caused by the condition, but the treatment , as vitiligo isn鈥檛 painful or dangerous.

鈥淯sually, people [with vitiligo] are asymptomatic in terms of physical symptoms, but it can cause a lot of emotional hardship,鈥� says at Indiana University, who led two trials of the new ruxolitinib cream treatment.

The cream, which is already available in the US, is sold under the name Opzelura. It treats non-segmental vitiligo, which occurs when symmetrical white patches appear on both sides of the body. This is thought to be caused by the immune system attacking melanocytes, the cells that make the pigment melanin, which gives skin colour.

The treatment is the first drug to be robustly tested that acts directly on the pathway that causes vitiligo, says at Vitiligo Support UK. 鈥淭hat鈥檚 why this [decision] is such a landmark,鈥� she says.

Ruxolitinib works by inhibiting two enzymes that cause . Existing treatments, like steroid creams, can restore some pigment, but suppress immune function more broadly.

, published in 2022, found that the drug increased pigmentation and reduced the noticeability of vitiligo patches compared with a placebo cream. This occurred (vitiligo is more noticeable on darker skin), and in more than a third of those who came off the drug after the trial.

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The National Institute for 91色情片 and Care Excellence (NICE) weighed up these results in the past, but judged ruxolitinib to for use on the NHS. Now, it says the cream should be made available to people aged 12 and older with non-segmental vitiligo when other topical treatments haven鈥檛 worked or are unsuitable.

Vitiligo, which , varies in severity. Some people have just a few small patches, while for others they can be large, red, inflamed or discoloured.

鈥淧atients and clinicians sometimes think we shouldn鈥檛 treat vitiligo, [because] it doesn鈥檛 kill you [and] it鈥檚 not painful,鈥� says at the British Association of Dermatologists. But vitiligo can have serious complications, such as a higher risk of .

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Natalie Ambersley 鈥� a vitiligo ambassador for the charity , which supports people with physical differences 鈥� says that people shouldn鈥檛 feel judged for treating the condition, but adds that after spending years using existing treatments, she won鈥檛 be seeking out ruxolitinib. 鈥淚鈥檝e learned to accept my skin,鈥� she says. 鈥淲e鈥檙e [all] unique and we can embrace what we look like.鈥�

鈥淚t鈥檚 great that there are people who love the skin they鈥檙e in, but that鈥檚 not for everyone,鈥� says Rush.

An oral version of ruxolitinib, which is used to treat some cancers and rheumatoid arthritis, , including lymphoma, heart problems and serious infections. But these have not been reported with the topical version. In the two vitiligo trials, ruxolitinib caused only mild side effects, including acne and itchiness. 鈥淭here is super minimal systemic absorption,鈥� says Eleftheriadou.

Ruxolitinib is also thought to be safer than steroid creams, which can cause skin thinning with long-term use. People with severe vitiligo may also be offered ultraviolet therapy, but this isn鈥檛 widely accessible.