Despite the fact that wearing SPF daily should already be a step that is firmly ingrained in your morning skincare routine (alongside brushing your teeth and taking a shower), it’s probably about this time of year - when the annual UK heatwave hits and your summer holiday is looming - that you start taking it seriously.

That means you’re probably going to be on the hunt for a sunscreen with bolstered protection. Before now, the highest SPF available to buy was 50. But now could be the time to shelve it, because SPF 100 is officially a thing, and there is some very important scientific evidence to suggest that we should all be wearing it.

In a 2018 study in the Journal of The American Academy of Dermatology, 199 men and women at a sunny ski resort in Vail, Colorado were given two tubes of SPF - one contained SPF 50 and the other, SPF 100. Participants didn’t know which one was which, as one tube was marked ‘left’ and the other marked ‘right’ - the labels indicated which side of the face they were required to apply the SPF to.

After application, participants were left to go about their business around the resort for the day.

The following day, a dermatologist evaluated erythema - reddening of the skin, AKA sunburn - and concluded that out of 199 people, 110 were more sunburned on the side of their face where they had applied the SPF 50, compared to just 10 people on the side they’d applied SPF 100 to.

In short, the study showed that SPF 100 is 11 times more effective at preventing sunburn than SPF 50 - and that’s impressive to say the least.

Sunscreen works to shield skin from the UV radiation that is emitted from the sun, so by wearing it you’re able to extend the amount of time you can spend in the sun without getting burnt.

While we would never advise sitting in it for long periods of time - or wearing anything lower than SPF30 - you can still tan while wearing SPF 100. 

In short, yes. Sunscreen simply extends the amount of time until burning takes place, it doesn’t actually prevent skin from tanning (and, actually, when your skin changes colour it’s a sign that the DNA has been damaged which is why dermatologists and skin experts agree it should generally be avoided), so if unprotected skin takes five minutes to burn, applying SPF100 would mean you could technically sit in the sun for 100x as long before skin burns.

However, it’s worth noting that there is no SPF that can protect skin 100% from UV rays (SPF50 sheilds against 98%) and all sunscreen should be re-applied every couple of hours and after swimming or sweating.

While SPF 100 is more readily available to buy in the US than it is here (if you’re heading there soon, here are a couple more beauty brands to know about and treat yourself to), Neutrogena’s Ultra Sheer Dry-Touch SPF 100 can be bought on Amazon. 

According to Dr Anjali Mahto, consultant dermatologist at Skin 55, the sun is the biggest environmental culprit in accelerated skin ageing (cue wrinkles and pigmentation) which is why it really pays to apply a daily broad spectrum SPF to sun-exposed areas such as the face, neck and hands.

If you aren’t sure when to slot SPF into your skincare routine, Dr Mahto suggests that it should be applied after serum and moisturiser in the morning. Make sure enough time is given for each layer of products to dry and absorb into the skin before applying the next layer. If you’re prone to acne, make sure your SPF is oil-free and non-comedogenic, so that it won’t clog your pores.

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