What is SPF in sunscreen and why is it important?

What is SPF?

There’s a common perception that the SPF number on a sunscreen simply indicates how powerful it is. In the minds of many of us, a higher SPF number means the sunscreen is going to do a far better job of protecting us.

This is both true and untrue. SPF stands for “Sun Protection Factor” (which doesn’t really tell us much, to be fair). What it means is how much longer the sunscreen is going to protect you from UVB rays (more on those later) than if you were out in the sun with zero protection. 

In other words, the SPF number tells you just how much longer your skin will be able to withstand UVB rays before it starts to burn. An SPF15, for example, should protect you for 15 times longer than wearing nothing at all. If you usually burn in 15 minutes, then it should take 225 minutes for you to burn if wearing an SPF15 sunscreen. An SPF4 sunscreen is theoretically just as powerful as an SPF50, but its effect will wear off much faster.

Bear in mind that we also need to take into account things like sweating and splashing around in the water, which make sunscreen less effective. To be on the safe side, the rule of the thumb is to re-apply every two hours. 

Also, not all sunshine is created equal. By this we mean that the noon sun on a summer’s day is more powerful (meaning you burn more quickly) than, say, 7am sunshine in the middle of winter. Plus, the UV changes from day to day, and doesn’t always correlate with the outside temperature. 

How is SPF calculated?

By scientists in a lab! They recreate the conditions in which the sun is at its highest and hottest and see what happens to skin exposed to UVB rays with and without the sunscreen in question.

What’s the difference between UVA and UVB?

Ah! We’re glad you asked, because this is a goodie. So, as we mentioned earlier, the SPF in sunscreen protects you against UVB rays only. UVB rays are the ones that cause sunburn. UVA rays, on the other hand, are the sneaky assassins that penetrate the skin’s layers more deeply and contribute to sun exposure effects like premature ageing (wrinkles) and damage that can lead to skin cancer.

Which is to say, we don’t want to be soaking up too many UV rays at all if we can help it!* This is where broad spectrum sun protection comes in. Seeing “broad spectrum” on a label tells you that the sunscreen is going to protect you from both kinds of rays. Broad spectrum is what we want. Broad spectrum is king.

Which SPF is best?

We don’t know about you, but here at SunButter HQ (which extends to our local beaches and beyond) we like to apply our sunscreen and know that we’re protected for as long as possible —partly because we’re frothers who like to frolic outdoors for extended periods of time, and partly because we’re lazy. So, we’re SPF50 kids.

Of course, some sun protection is better than none, so if you happen to find yourself renting a beach house at some remote location with access to only SPF4 (a very specific situation), then go for that SPF4! Just be extra mindful and remember that you’ll need to apply far more frequently (no falling asleep on the beach for hours, folks).  

SPF and make up 

If you’re a make-up wearer, you might have noticed that foundations, tinted moisturisers and BB creams sometimes contain an SPF rating. This can be a great thing, because it ensures that any time you’re wearing your make-up, you’re somewhat protected (good news if you find yourself on a spontaneous boat trip, at a daytime rooftop party or even just standing in the sun waiting awhile for your takeaway coffee).

However, it’s important to note that most of these products only have an SPF rating of 15, meaning that they won’t offer as long-lasting protection. To better protect yourself, experts recommend wearing at least SPF30 sunscreen on your face (and other exposed areas of your body, such as your ears, neck and hands). Sunscreen needs to be applied underneath your make up — and it’s not a good idea to combine your sunscreen and make up together.

SunButter SPF50 tinted sunscreen can be a great way to make sure you’re giving your skin sun protection that lasts longer while also sporting a bronze glow. 

So, that’s SPF in a (kind of big) nutshell, friends. The bottom line is to know what you’re putting on your skin and how long it is likely to protect you before you get out into the big, wide world.

*To circle back to the question of UV rays: we do need a certain amount of UV action in our bods. It’s through UV rays that we’re able to soak up Vitamin D from the sun, which is important for things like strong bones and muscles. In a crazy paradox, UV is both the chief cause of skin cancer and the best way to get natural Vitamin D. Wild, huh? Even still, experts don’t recommend running out into the midday sun sans protection to beef up your Vitamin D count (if you’re deficient, your GP may suggest Vitamin D tablets). If the UV rating is over three, you know the advice: slip (on a shirt), slop (on some sunscreen) and slap (on a hat).