How does sunscreen work? What you need to know about SPF, UVA and UVB
Summer is finally here, holidays are on the horizon and bottles of sunscreen are being dusted off from the back of the bathroom cupboard.
This is often the time of the year when we start thinking about skin protection – even if we know it should be a year-round concern.
Some of the UK’s most popular sunscreens have failed safety tests, offering far less protection than promised.
But from UVA and UVB to SPF, what do all the acronyms on the bottle mean – and what’s important for protecting your skin?
Here is what you need to know.
What is the difference between UVA and UVB?
There are two main types of UV (ultraviolet) rays in sunlight – UVA and UVB.
A simple way to remember the difference is that A is for ageing and B is for burning.
UVB reaches the outer layer of the skin, the epidermis, causing most sunburn.
UVA gets deeper and it is associated with ageing. It damages the collagen and elastin in the skin and causes wrinkles.
Both types of UV can damage the DNA in our skin cells and cause skin cancer.
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What is SPF?
SPF stands for Sun Protection Factor and the number represents how much UVB it allows to reach your skin.
A sunscreen with SPF15 allows one-fifteenth of the sun’s UVB rays in, or about 7%.
The amount of UV rays filtered depends on the level of SPF.
• SPF15 blocks 93% of UVB rays
• SPF30 blocks 96.7% of UVB rays
• SPF50 blocks 98% of UVB rays
The numbers can be used as a guide to how long you are protected from burning, compared to if you weren’t wearing an SPF sunscreen.
So if you would normally burn after 10 minutes, and you’re wearing SPF30, you could – in theory – spend around five hours in the sun with a reduced risk of sunburn (because 10 x 30 = 300 minutes).
However, that calculation should be taken with a pinch of salt, because no sunscreen actually blocks 100% of UV rays. That is reflected in the fact that in the EU, the maximum SPF rating is 50+.
The calculation is also based on the sunscreen being applied exactly as directed.
Pic: PA
What is the star rating?
While the SPF rating will tell you how well a suncream protects against UVB, star ratings are the indicator for UVA protection.
You should look for a high star rating of four or five stars, according to Cancer Research UK, or “UVA” in a circle, which indicates it meets the EU’s minimum standard.
What is the UV index?
The UV index tells you how strong the sun’s rays are – the higher the number, the stronger it is.
On a scale of 1 to 9+, a rating of three or more indicates the sun is strong enough to cause damage and you should use sun protection.
UV rays are generally strongest between 11am and 3pm and can be strong enough to damage your skin from mid-March to mid-October in the UK, even if it’s cold or cloudy.
You can check the UV index on weather forecasting websites or apps or by searching online.
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How does sunscreen actually work?
There are two types of UV filters and sunscreens often contain a combination.
Mineral sunscreen ingredients include titanium dioxide and zinc oxide, which act as a physical barrier that reflects and scatters UV rays away from the skin.
Chemical sunscreen ingredients include aminobenzoic acid, avobenzone, octisalate, octocrylene, and oxybenzone.
These absorb the UV rays so they don’t damage your skin.
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Cancer Research UK’s tips for applying sunscreen:
• Use a lotion, pump-spray or roll-on over an aerosol, as the coverage from aerosols can be patchy and thin.
• Put enough on, applying sunscreen evenly and thickly.
• Reapply regularly, even if your sunscreen says it’s “once a day” or “water resistant”.
• Don’t rely on SPF in moisturiser or make-up, as often these products don’t give enough protection on their own.
• Check the expiry date on your sunscreen to make sure it’s still providing protection.
Liverpool have won the Premier League title after a 5-1 victory over Tottenham at Anfield.
Arne Slot’s men did it in impressive style, turning over Spurs in a convincing win.
It was a rocky start for the Reds after Dominic Solanke put the north London side ahead.
However, fortunes quickly changed in the first half as Liverpool scored three times without a response.
Captain Virgil van Dijk (centre) celebrates. Pic: Reuters
Salah on his knees in celebration after the final whistle. Pic: AP
Liverpool’s Harvey Elliott (below) and Jarell Quansah celebrate after full-time. Pic: PA
Slot cheers after the full-time whistle. Pic: AP
In the second half, it took until the 63rd minute for Mohamed Salah to make it 4-1 before a fifth followed.
The Reds have won the title in manager Arne Slot’s first season in charge, and move level with fierce rivals Manchester United on 20 league championships.
But it makes them arguably the most successful English club ever as they have won more European Cup or Champions League titles.
Liverpool captain Virgil van Dijk told Sky Sports after the final whistle: “It’s special and it’s something that we don’t take for granted. It’s amazing.
“A lot of emotions before the game, during the whole week, but we got the job done and we (are) truly deserved champions of England. (Liverpool is) the most beautiful club in the world and I think we deserve all of this. Let’s enjoy the next couple of weeks and let it sink in.”
Liverpool’s Kostas Tsimikas poses with a Premier League trophy cut out. Pic: Reuters
Manager Arne Slot and his team after the final whistle. Pic: AP
Slot took over last summer from Jurgen Klopp, who guided them to their previous and maiden Premier League title triumph in 2020, when the COVID-19 lockdown saw matches played behind closed doors.
He is the first Dutch manager to win the Premier League and the fifth man to do so in a debut campaign after Jose Mourinho, Carlo Ancelotti, Manuel Pellegrini, and Antonio Conte.
Speaking to Sky Sports he said: “They [the players] did an outstanding job today. The main job was to win. Everyone said we had got it already. But we had to make sure and we got over the line.”
Several players, including Alisson Becker, Trent Alexander-Arnold, Virgil van Dijk, and Mohamed Salah, played leading roles in both the 2025 and 2020 campaigns.
Van Dijk and Salah recently signed new contracts extending their careers at the club.
Mohamed Salah takes a selfie with fans after scouring the fourth Liverpool goal. Pic: AP
Fans at Anfield during the game. Pic: AP
Fans in the stands at Anfield before full-time. Pic: Reuters
Liverpool will have to wait until the final game of the season – at home to Crystal Palace on 25 May – to be presented with the Premier League trophy.
It will be the first time the club’s fans will have seen their side lift the top-flight title in person since 1990.
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Two pro-Palestinian demonstrators have thrown red powder on Tower Bridge – just moments before leading runners in the London Marathon went past.
The protesters were arrested on suspicion of causing a public nuisance and remain in custody, said the Metropolitan Police.
A video shared by Youth Demand, which is calling for a trade embargo on Israel, shows two people jumping over a barrier that separates spectators from the race course.
The pair, wearing t-shirts that say “Youth Demand: Stop Arming Israel”, are then seen standing in the middle of the road on the bridge.
Pic: LNP
They throw red powder in the air as an official marathon car goes past displaying the race time.
A motorbike with a cameraman on board continues along the route, while a second motorbike stops and one of the riders gets off and pushes the pair out of the way, just before the men’s elite runners pass.
Several police officers then jump over the barrier and detain the pair, the footage shows.
There appeared to be no impact on the marathon.
More than 56,000 participants were expected to take part in the 26.2-mile race through the capital.
Sabastian Sawe of Kenya won the men’s elite race in a time of two hours, two minutes and 27 seconds, while Ethiopia’s Tigst Assefa shattered the women’s-only world record in two hours, 15 minutes and 50 seconds.
Assefa beat the previous best of two hours, 16 minutes and 16 seconds set last year in London by Kenyan Peres Jepchirchir.
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Pic: LNP
The Metropolitan Police said in a statement: “At around 10.38am, two protesters from Youth Demand jumped over barriers at Tower Bridge and threw red paint on to the road.
“Marathon event staff intervened to remove the protesters from the path of the men’s elite race which was able to pass unobstructed.”
The force added that they were “quickly supported by police officers who arrested the protesters on suspicion of causing a public nuisance”.
The Met said the paint “appeared to be chalk-based” and was not expected to “present a hazard to runners yet to pass this point”.
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