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There’s something you should know about SPF 15 sunscreen

That tube of SPF 15 you’ve got packed in your beach bag, ready for when summer hits? Yeah, it’s time to chuck that sucker out and buy something better.

Statistics show two in three Australians will suffer from skin cancer before they turn 70, which means putting the right sunscreen on is super important.

But recent research suggests that while people may be buying the right sunscreen, they might be using it the wrong way.

A recently conducted experiment showed that sunscreen is effective when applied at between 1.3 and 2.0 milligrams per square centimetre.

However, plenty of people only apply 0.75 square centimetres.

“People are typically getting much less protection than they think,” Antony Young, an author of the study and professor of experimental photobiology at King’s College London, told The Guardian.

“For example, if you get SPF20 and use at a lower thickness of 0.75 milligrams per centimetre squared, your level of protection could be as low as SPF4.”

As a result, Nina Goad of the British Association of Dermatologists said, “This research demonstrates why it’s so important to choose an SPF of 30 or more. In theory, an SPF of 15 should be sufficient, but we know that in real-world situations, we need the additional protection offered by a higher SPF.”

In case you need any more convincing, the Cancer Council of Australia recommend coating yourself in sunscreen “that is labelled broad-spectrum, water-resistant and SPF30+ or above”.

What do the various SPF numbers even mean?

SPF stands for ‘sun protection factor’, which isn’t really all that difficult to wrap your head around.

However, there is no shortage of half-truths, rumours and flat-out lies (which we won’t list here, so as to save on any confusion) about what the number following those three letters actually means.

The number indicates what fraction of the sun’s harmful UV rays can reach you through the sunscreen.

Which, as Professor Terry Slevin pointed out, “provides a screen, not a block“.

So when you slather on SPF 15, one-fifteenth of the sun’s rays are getting through.

By comparison, SPF 30 allows in one-thirtieth, while SPF 50 gets you protection from all bar one-fiftieth of the UV rays.

However, while the difference between 30 and 50 looks and sounds pretty dramatic, it’s actually not much at all.

The Cancer Council points out, “SPF50+ only offers marginally better protection than SPF30+. SPF50+ filters out 98% of UVB radiation, while SPF30+ blocks out 96.7% of UVB.”

As such, it’s important to apply – and re-apply, at least every two hours – SPF 50 the same way you would SPF 30.

About the author

Joe was Junior Vice-President at Compu-Global-Hyper-Mega-Net until it was bought out by Bill Gates. He now subedits for Conversant Media and considers it a step up.

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