Summer is nearly here. But rather than getting out the sunscreen, some TikTokers are urging followers to chuck it out and go sunscreen-free.

They claim it’s healthier to forgo sunscreen to get the full benefits of sunshine.

Here’s the science really says.

How does sunscreen work?

Because of Australia’s extreme UV environment, most people with pale to olive skin or other risk factors for skin cancer need to protect themselves. Applying sunscreen is a key method of protecting areas not easily covered by clothes.

Sunscreen works by absorbing or scattering UV rays before they can enter your skin and damage DNA or supportive structures such as collagen.

When UV particles hit DNA, the excess energy can damage our DNA. This damage can be repaired, but if the cell divides before the mistake is fixed, it causes a mutation that can lead to skin cancers.

The most common skin cancers are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Melanoma is less common, but is the most likely to spread around the body; this process is called metastasis.

Two in three Australians will have at least one skin cancer in their lifetime, and they make up 80% of all cancers in Australia.

Around 99% of skin cancers in Australia are caused by excessive exposure to UV radiation.

Excessive exposure to UV radiation also affects the appearance of your skin. UVA rays are able to penetrate deep into the skin, where they break down supportive structures such as elastin and collagen.

This causes signs of premature ageing, such as deep wrinkling, brown or white blotches, and broken capillaries.

Sunscreen can help prevent skin cancers

Used consistently, sunscreen reduces your risk of skin cancer and slows skin ageing.

In a Queensland study, participants either used sunscreen daily for almost five years, or continued their usual use.

At the end of five years, the daily-use group had reduced their risk of squamous cell carcinoma by 40% compared to the other group.

Ten years later, the daily use group had reduced their risk of invasive melanoma by 73%

Does sunscreen block the health-promoting properties of sunlight?

The answer is a bit more complicated, and involves personalised risk versus benefit trade-offs.

First, the good news: there are many health benefits of spending time in the sun that don’t rely on exposure to UV radiation and aren’t affected by sunscreen use.

Sunscreen only filters UV rays, not visible light or infrared light (which we feel as heat). And importantly, some of the benefits of sunlight are obtained via the eyes.

Visible light improves mood and regulates circadian rhythm (which influences your sleep-wake cycle), and probably reduces myopia (short-sightedness) in children.

Infrared light is being investigated as a treatment for several skin, neurological, psychiatric and autoimmune disorders.

So what is the benefit of exposing skin to UV radiation?

Exposing the skin to the sun produces vitamin D, which is critical for healthy bones and muscles.

Vitamin D deficiency is surprisingly common among Australians, peaking in Victoria at 49% in winter and being lowest in Queensland at 6% in summer.

Luckily, people who are careful about sun protection can avoid vitamin D deficiency by taking a supplement.

Exposing the skin to UV radiation might have benefits independent of vitamin D production, but these are not proven. It might reduce the risk of autoimmune diseases such as multiple sclerosis or cause release of a chemical that could reduce blood pressure. However, there is not enough detail about these benefits to know whether sunscreen would be a problem.

What does this mean for you?

There are some benefits of exposing the skin to UV radiation that might be blunted by sunscreen. Whether it’s worth foregoing those benefits to avoid skin cancer depends on how susceptible you are to skin cancer.

If you have pale skin or other factors that increase you risk of skin cancer, you should aim to apply sunscreen daily on all days when the UV index is forecast to reach 3.

If you have darker skin that rarely or never burns, you can go without daily sunscreen – although you will still need protection during extended times outdoors.

For now, the balance of evidence suggests it’s better for people who are susceptible to skin cancer to continue with sun protection practices, with vitamin D supplementation if needed.

Katie Lee, PhD Candidate, Dermatology Research Centre, The University of Queensland and Rachel Neale, Principal research fellow, QIMR Berghofer Medical Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

So, you got your eyesight tested and found out you need your first pair of glasses. Or you found out you need a stronger pair than the ones you have. You put them on and everything looks crystal clear. But after a few weeks things look blurrier without them than they did before your eye test. What’s going on?

Some people start to wear spectacles for the first time and perceive their vision is “bad” when they take their glasses off. They incorrectly interpret this as the glasses making their vision worse. Fear of this might make them less likely to wear their glasses.

But what they are noticing is how much better the world appears through the glasses. They become less tolerant of a blurry world when they remove them.

Here are some other things you might notice about eyesight and wearing glasses.

Lazy eyes?

Some people sense an increasing reliance on glasses and wonder if their eyes have become “lazy”.

Our eyes work in much the same way as an auto-focus camera. A flexible lens inside each eye is controlled by muscles that let us focus on objects in the distance (such as a footy scoreboard) by relaxing the muscle to flatten the lens. When the muscle contracts it makes the lens steeper and more powerful to see things that are much closer to us (such as a text message).

From the age of about 40, the lens in our eye progressively hardens and loses its ability to change shape. Gradually, we lose our capacity to focus on near objects. This is called “presbyopia” and at the moment there are no treatments for this lens hardening.

Optometrists correct this with prescription glasses that take the load of your natural lens. The lenses allow you to see those up-close images clearly by providing extra refractive power.

Once we are used to seeing clearly, our tolerance for blurry vision will be lower and we will reach for the glasses to see well again.

The wrong glasses?

Wearing old glasses, the wrong prescription (or even someone else’s glasses) won’t allow you to see as well as possible for day-to-day tasks. It could also cause eyestrain and headaches.

Incorrectly prescribed or dispensed prescription glasses can lead to vision impairment in children as their visual system is still in development.

But it is more common for kids to develop long-term vision problems as a result of not wearing glasses when they need them.

By the time children are about 10–12 years of age, wearing incorrect spectacles is less likely to cause their eyes to become lazy or damage vision in the long term, but it is likely to result in blurry or uncomfortable vision during daily wear.

Registered optometrists in Australia are trained to assess refractive error (whether the eye focuses light into the retina) as well as the different aspects of ocular function (including how the eyes work together, change focus, move around to see objects). All of these help us see clearly and comfortably.

What about dirty glasses?

Dirty or scratched glasses can give you the impression your vision is worse than it actually is. Just like a window, the dirtier your glasses are, the more difficult it is to see clearly through them. Cleaning glasses regularly with a microfibre lens cloth will help.

While dirty glasses are not commonly associated with eye infections, some research suggests dirty glasses can harbour bacteria with the remote but theoretical potential to cause eye infection.

To ensure best possible vision, people who wear prescription glasses every day should clean their lenses at least every morning and twice a day where required. Cleaning frames with alcohol wipes can reduce bacterial contamination by 96% – but care should be taken as alcohol can damage some frames, depending on what they are made of.

When should I get my eyes checked?

Regular eye exams, starting just before school age, are important for ocular health. Most prescriptions for corrective glasses expire within two years and contact lens prescriptions often expire after a year. So you’ll need an eye check for a new pair every year or so.

Kids with ocular conditions such as progressive myopia (short-sightedness), strabismus (poor eye alignment), or amblyopia (reduced vision in one eye) will need checks at least every year, but likely more often. Likewise, people over 65 or who have known eye conditions, such as glaucoma, will be recommended more frequent checks.

An online prescription estimator is no substitute for a full eye examination. If you have a valid prescription then you can order glasses online, but you miss out on the ability to check the fit of the frame or to have them adjusted properly. This is particularly important for multifocal lenses where even a millimetre or two of misalignment can cause uncomfortable or blurry vision.

Conditions such as diabetes or high blood pressure, can affect the eyes so regular eye checks can also help flag broader health issues. The vast majority of eye conditions can be treated if caught early, highlighting the importance of regular preventative care.

James Andrew Armitage, Professor of Optometry and Course Director, Deakin University and Nick Hockley, Lecturer in Optometric Clinical Skills, Director Deakin Collaborative Eye Care Clinic, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.