"If you only use one product in your skincare regime, please let it be an SPF," writes top aesthetic doctor David Jack in his new guide to looking good Vain Glorious, £7.79 co-written with Jeremy Langmead .
As we all know by now, sun cream is vital to protect us against prematurely ageing UVA rays, sunburn-inducing UVB rays and ultimately, skin cancer. But that's only if we apply it correctly and often enough, which most of us don't.
So what does using sun cream properly look like? We took the advice of Dr David Jack, as well as cosmetic dermatologist and Get The Gloss Expert Dr Tapan Patel and dermatologist and skin cancer surgeon Dr Andrew Birnie, founder of Altruist Sunscreen , speaking on the BBC's Sliced Bread podcast , to debunk some of the common misconceptions around SPF.
From whether water-resistant suncream does what it says, to the truth about the SPF protection in our cosmetics and mositurisers, here’s how to stay safe and sunburn-free this summer and beyond.
What does the sun protection factor actually mean?
“‘SPF’ stands for Sun Protection Factor and is used to how long the protection provided by the sunblock will last," says Dr Patel. "If you burn within 20 minutes of exposure to the sun, an SPF 15 is formulated to protect you 15 times longer (around five hours).”
So, the SPF factor denotes how many times longer you can stay out in the sun before your skin turns red. If you normally go red after 20 minutes in the sun in June, an SPF 50 will allow you to stay out for 50 times that length (i.e. 50 x 20 minutes). The protection factor depends on how quickly you personally turn red in the climate you are in.
“An SPF 50 will provide you with longer protection, meaning it should theoretically need to be applied less frequently than say, an SPF 30," says Dr Patel. "It also blocks a higher percentage of UVB rays from the sun, meaning you are less likely to burn or experience skin damage.”
Is SPF 15 double the protection of SPF 30?
Simply, yes, says Dr Birnie, when it comes to the length of time you can stay out. As for the percentage of UVB rays that they block, they both keep out surprisingly high levels of rays. "SPF15 allows 93.3 per cent UVB to be blocked, SPF 30 allows 96.7 per cent to be blocked, " says Dr Birnie. "If you spin that around SPF30 allows 3.3 per cent of UVB through, SPF15 allows 6.7 per cent through, so it is double the protection."
What's the difference between mineral/physical SPFs and chemical suncreams and which is better?
Neither is better or worse than the other when it comes to warding off rays, they just act differently (however those with sensitive skin often fare better with mineral sunscreen )
"Mineral means it comprises of mineral sunscreen, usually zinc oxide or titanium dioxide," Dr Birnie explains. "Mineral works by reflecting or scattering UVA rays as they hit skin while chemical causes a chemical reaction which causes the UV energy to change into heat which is then lost."
Chemical sunscreens include compounds such as avobenzone, octinoxate and oxybenzone, as well as many, others writes Dr David Jack in Vain Glorious. Is oxybenzone toxic? Despite what Davis Jack calls a sensationalist piece in the New Yprk Times and elsewhere, "oxybenzone, has not actually been shown to cause any harm to humans. I would therefore say: be sensible. What we do know for sure is that skin cancers can be lethal and that UV is the main cause of them, so we would be particularly silly to not use UV filters in our skincare based on some overhyped and underresearched hearsay. At least until we have further solid evidence to the contrary."
Which is better? That comes down to personal preference, says Dr Jack. "I prefer chemical screens. They are lighter in weight, tend to be less comedogenic (less likely to block pores and cause breakouts) and you don’t need to use as much. Physical screens need to be applied quite thickly to achieve the level of protection they say they provide. In fact, you may need to apply as much as two teaspoons to the face and neck alone to obtain the cover stated." He adds that mineral suncreams may leave a reflective white film on the skin, "which might be problematic for darker skin types."
Sometimes brands will offer sunscreens that contain a mixture of both. Find out more in our g uide to sun cream ingredients.
Which comes first - suncream or moisturiser?
Usually, SPF is your last step after moisturiser. Especially if it's a mineral suncream it acts as a barrier. If you put moisturiser on top it can dilute the effectiveness of your SPF underneath or even rub it off.
Why do I need UVA and UVB protection and what do they mean?
Sunlight contains UVA and UVB rays both of which can cause skin damage and cancer. An easy way to remember what they do is UV-A is 'Ageing' and UV-B is 'Burning'. You need to look for suncream labelled broad-spectrum which covers both.
What does the star or PA+ rating on sun cream mean?
UVA protection is shown by a star rating. You will see a star rating of between zero and five stars on UK sunscreens. UVA protection is measured as ratio of the UVB protection. "A five-star rating means that UVA protection is equivalent to the UVB protection." The higher the star rating, the better. Four or five stars is what you need.
UVA in a circle means it meets EU standards and has at least one-third of the protection offered by the UVB rating, according to which.co.uk .
Your bottle might also have PA+ (or even PA++++) on the label which is a rating system from Japan indicating how much UVA protection is offered (the more + the better). However, this is not considered gold standard as 'broad-spectrum SPF', according to Paula's Choice, because it only measures the protection against UVA turning the skin brown (known as PPD, persistent pigment darkening) and not everyone skin reacts the same way.
How often should you apply sun cream?
“Top up your sunblock once every four hours or so, but it is important to read the label on your sunblock to follow the directions of use, as this differs from brand to brand and SPF," says Dr Patel. "You should apply sunblock every morning, even if you are not tanning on the beach. It helps to protect your skin from harmful UVA and UVB rays, as well as act as an anti-ageing protocol. It is much better to be safe than sorry.”
How much suncream should I use?
More than you think! The recommended amount equates to a teaspoon on each arm and one for the face and neck in order to get the protection it says on the pack. SPF factor is predicated on you using quite a lot. Dr Birnie recommends using enough cream that it looks white to start with and applying it in direction of hair growth so it fully sinks in.