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Monday’s medical myth: SPF50+ sunscreen almost doubles the protection of SPF30+

It’s likely Australia’s sunscreen regulations will change this summer, enabling manufacturers to label their products as SPF50+. The sunscreen industry has championed the proposed change, led by Standards…

SPF50+ only increases protection by 1.3%. Flickr/the half blood prince

It’s likely Australia’s sunscreen regulations will change this summer, enabling manufacturers to label their products as SPF50+.

The sunscreen industry has championed the proposed change, led by Standards Australia, because the SPF50+ label will prompt many Australians to buy new product, thinking they’re getting significantly higher protection from the sun.

But what does SPF50+ actually mean? And will it provide better protection?

The Sun Protection Factor (SPF) indicates the amount of UVB radiation that can reach the skin (and cause sunburn) with sunscreen, compared with no sunscreen.

In other words, SPF ratings indicate the multiples of time you could spend unprotected in the sun without burning, assuming the UV rating was constant.

But no sunscreen offers full protection from the sun. And the increment in UVB filtering between SPF30+ and SPF50+ is small, increasing protection from 96.7% to 98%. That’s a 1.3% increase, not almost double, as many people may think when making a purchasing decision.

Whether it’s SPF30+ or 50+, sunscreen alone isn’t enough to protect you against skin cancer. Flickr/Liberalthug

Many sunscreens contain a combination “inorganic” (minerals, produced using chemical processes) and “organic” (chemical) ingredients.

Inorganic ingredients both absorb and reflect UV radiation, whereas organic ingredients only absorb. This means the energy from the UV radiation is used to convert the organic chemical into another form. But you wouldn’t feel any heat produced from such a change.

As our understanding of sunscreen’s role in protecting consumers from skin cancer evolves, sunscreen manufacturers are offering other protections. “Broad spectrum” sunscreens now protect against UVB and UVA radiation, which we now know contributes to the development of skin cancer.

Inorganic ingredients, such as titanium dioxide and zinc oxide, may offer a broad spectrum protection but they simply reflect the UV. They also tend to be gentler on the skin.

So what’s likely to happen if and when SPF50+ comes on to the market?

My concern is that consumers will think the increased SPF factor offers significantly better protection than the products they’re accustomed to. And if this leaves Australians using less sunscreen and neglecting other protection behaviours, we’re likely to see a future spike in skin cancers.

Australia has one of the highest rates of skin cancer in the world due to our climate and large fair-skinned population. More than 10,300 Australians are diagnosed with a melanoma each year and an estimated 434,000 people are treated for one or more non-melanoma skin cancers.

Despite the popular slip, slop, slap campaign from the 1980s, more than 1,830 Australians die from a skin cancer each year. Even though it’s largely preventable.

Skin cancers form when skin cells are damaged by UV radiation penetrating the skin. Tanning without burning can still cause damage – if you’ve been exposed to enough UV to cause tanning, sufficient damage has been done to cause cancer.

It doesn’t matter whether you use SPF30+ or SPF50+ sunscreen, the best way to protect yourself from skin cancer is with a combination of clothing (slip), sunscreen (slop), hat (slap), sunglasses (slide) and shade (seek), whenever the UV index reaches three or above.

Tips for applying sunscreen:

  • Make sure your sunscreen is at least SPF30+, water resistant and broad spectrum, which protects you from UVB and UVA;

  • Apply 20 minutes before you go outdoors and reapply every two hours;

  • Use at least one teaspoon of sunscreen for each limb, your face and the front and back of your body;

  • Check the use-by date;

  • Never rely on sunscreen – whether it’s SPF30+ or SPF50+ – as your only defence against the sun.

Join the conversation

6 Comments sorted by

    1. Adam Zielinski

      logged in via Facebook

      In reply to Cameron Murray

      The figures quoted here are a little misleading. "...between SPF30+ and SPF50+ is small, increasing protection from 96.7% to 98%. That’s a 1.3% increase, not almost double, as many people may think when making a purchasing decision."

      Sure that is a 1.3% increase in absolute terms, however this means that only 2% of the radiation is getting throught with SPF50+, vs 3.3% for SPF30+. Although 3.3% isn't quite double 2%, it is a more accurate was of describing the increase in protection than just saying "a 1.3% increase".

      Would you expect something that offers "double" 96.7% to give 193.4% protection?

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    2. Adam Zielinski

      logged in via Facebook

      In reply to Adam Zielinski

      Another way to look at it is to compare something that gives 90% protection vs something that gives 100% protection. Would you say that the 100% protection product blocks infinitely better than the 90% protection product, or would you say "only 10% more protection" ?

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    3. Greg Adcock

      Scientist

      In reply to Adam Zielinski

      Adam,

      your view is completely correct and I wonder whether this article should actually be withdrawn. The idea that 50+ is not double the level of protection as 30+ might be true if we phrase it that way but it seems like this way of viewing it is just used so it can be shot down (ie a straw man).

      So what exactly is the myth here? Just to make up some numbers, if it takes 2 hours to burn using SPF30+ and almost 4 hours (ie because the amount of UV penetrating a person's skin is almost half) using SPF50+, the average person would say, "wow double the protection". I think they would be right.

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  1. John Harland

    bicycle technician

    How do you get the orange stains from sunscreen out of white clothing? The stains make new clothing look instantly shabby.

    If we want people to use something, we need to look at the practicalities, not just the laboratory figures.

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  2. Doug Cotton

    IT Manager

    I believe the comments have established that this is not a myth. SPF 30 and SPF 50 mean skin can be exposed to the sun 30 / 50 times longer than if unprotected without burning. Perhaps the biggest risk, however, is that people inevitably miss small areas of skin when applying cream.

    Other factors also affect an individual's resistance to sunburn, in particular the levels of superoxide dismutase (SOD) in his or her body. Hence it could be advisable to take supplements which raise your level of…

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