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Top derms answer our most burning SPF and sunscreen questions
August 11th 2020 / 0 comment
From how long SPF factors last, to the merits of reef-safe SPF, whether water-resistant sunblock is worth it and just what all those UV ratings really mean...
When it comes to SPF, are we using it correctly and are our sunscreens providing the protection we think?
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.
So what does that look like? We took the advice of 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, 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 and chemical suncream?
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."
Often brands will offer sunscreens that contain a mixture of both. Find out more in our guide to sun cream ingredients.
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 as 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 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 to apply it in direction of hair growth so it fully sinks in.
Do moisturisers and makeup with SPF provide enough protection?
No. “BB creams and foundations which claim to have an SPF are not substitutes for a good, protective sunblock. They rarely contain a high enough SPF to really protect the skin from sun damage, and should only really be applied in conjunction with a traditional sunblock," says Dr Patel.
Bear in mind you'd have to slather on a lot of SPF makeup or foundation every four hours (a whole teaspoon!) to get the same level of protection as a dedicated SPF.
Moisturisers are another matter as you are likely to put them on thickly enough. Here are the best broad-spectrum SPF facial skincare we trust to protect from damaging rays.
How effective is water-resistant suncream?
If you've ever slathered yourself in water-resistant sunblock, hopped in and out of the pool and somehow found yourself burning you'll know that water-resistant suncream has its limits. Water-resistant simply means the product has been tested under very specific lab conditions which include drip-drying after a hot tub session twice and not towelling down, the equivalent of taking two dips. "They then test how effective that sunscreen is, and as long as your SPF is at least 50 per cent of the labelled factor you can label it water-resistant," says Dr Birnie. On top of that, many of us towel-dry which compromises the effectiveness of your suncream. "I would always advocate reapplying sunscreen after going in the water."
Are cheaper sunscreens less effective?
While there are many high-end formulas on the market, it doesn't necessarily make them a better protectant against UVA and UVB. An inexpensive product will have been through the same tests as a luxury cream. The only difference will be that they might not feel as nice when you apply them. Altruist Sunscreen, developed as a social enterprise by Dr Birnie, is sold at the lowest price possible (£8 for two tubes) in utilitarian packaging in order for it to be accessible for everyone to minimise the risk of skin cancer.
Do I need reef-safe suncream?
Increasingly we're seeing 'reef safe' on bottles SPF and this is because high concentrations of some ingredients oxybenzone and oxynocate can cause coral bleaching (reef-safe sun creams don't contain them). Dr Birnie feels it's a moot point for most of us unless we are swimming in coral-rich waters with no tide, such as in a lagoon, where the bleaching ingredients can be more concentrated.
"Reef safe is a bit of a marketing tool," he says. "There are some studies that suggest that high concentrations of certain sunscreen in the water may cause some coral bleaching. "My advice to anyone who would be [swimming near coral] is that wearing UV protective clothing would be a far better option because if you're spending time snorkelling the suncream could potentially wash off anyway so you'll get better quality protection in UV clothing."
So in the end, which SPF is best?
Whether you want reef-safe, mineral or chemical is personal preference, but from a skin damage perspective Dr Birnie advises, "SPF factor 30 or 50 and something that's broad-spectrum (UVA/UVB) with the four or five stars [UVA rating] or the UVA in a circle."
Do I need to wear SPF inside or when it's cloudy?
In a word, yes - and when driving. Fifty per cent of UVA rays penetrate glass (depending on the glass, your car windscreen will likely have a filter on it but the side windows probably don't). Find out more on why you need to wear SPF indoors here.
As for wearing sunscreen when it's cloudy, this too is a wise precaution as the effects of UV damage over time can build up even if we never burn and only receive small doses. It's best to protect the areas of the skin such as the face that receive the most exposure, as Dr Birnie explains below.
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