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Can You Really Trust The SPF Number On Your Sunscreen?

Can You Really Trust The SPF Number On Your Sunscreen?

If you’re even the slightest bit into skincare, you already know the golden rule. In the words of Baz Luhrman: wear sunscreen. To avoid the sun’s rays is to avoid the potential for skin hyperpigmentation, premature ageing, and (of course!) cancer. As Australians we’ve had the importance of slopping on daily SPF drilled into us from the time we were kids, and most of us spend many years and dollars on finding our favourite formulations for face and body sunscreen. But what if the sunscreen products we rely on so heavily can’t be trusted?

In recent years, some popular brands have been exposed for marketing sunscreens at a higher SPF than they actually are. So, what does this mean? Has our diligent sunscreen application been in vain? To understand this, it’s important to understand the complicated nature of sunscreen formulation and testing in Australia and worldwide. In the same way that finding your perfect sunscreen can be a fickle process, they are just as fickle to formulate. To put it simply, both are wildly complicated.

If you look at the back of your sunscreen packaging, you’ll notice a list of active ingredients. These can include chemical or mineral filters and will be listed alongside a percentage. You may think that a higher percentage or number of UV filters would mean a higher SPF, but it is not nearly this simple. The way that filters interact with each other, interact with the other ingredients, and interact with the skin are all factors in determining SPF. Even if a brand is trying to develop a higher SPF version of a current product, this process can take months of work. It’s important to note that Western sunscreens are often developed to be worn outdoors in direct sunlight, so are often thicker and more water resistant. Asian sunscreens are developed for a more habitual daily application under makeup or indoors, so are often more comfortable yet less durable. It’s the highly complicated nature of sunscreen formulation that leaves room for SPF discrepancy between batches, personal usage and country of origin.

The testing process itself is an expensive endeavour, and unfortunately leaves a lot of room for error. The standardised SPF test ISO 24444 is performed in vivo (on human skin). As of yet, there is not a mechanised option that can accurately mimic the way that sunscreen interacts with human skin, so the ISO 24444 is still the international gold standard. While it is essentially the same test in every country, there are many human factors that can affect results, from the range of skin tones of volunteers to the pressure used by the tester when rubbing in the product. The container the formula is delivered to the lab in could affect the SPF, and there are even reports of testing bias, i.e. results coming back closer to a brand’s reported SPF than when tested blind.

The good news is that brands are starting to take more accountability, with many choosing to invest money into their own independent testing rather than relying on the report from their lab. So, what can we do about making sure we are adequately protected from the sun’s harmful UV rays? What we’ve always known: Slip, Slop, Slap. While sunscreen is important, it should never be relied on as a fail-safe line of defence. It’s just as important to wear protective clothing, hats, sunglasses, and actively avoid sun exposure during the hottest parts of the day. Using enough sunscreen is also grossly underestimated, which means not just relying on the SPF in your tinted moisturiser. Being sun smart doesn’t require understanding the chemistry behind each product, but it does require daily diligence and a holistic approach.


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