Your sun protection guide: SPF, UVB and UVA explained

Woman putting on SPF. (Getty Images)
People are often confused by the jargon on SPF bottles. (Getty Images)

With temperatures soaring this week, we all know we should be slapping on the suncream to protect our skin from sunburn.

But, though we like to think we’re SPF-aware, many of us get confused by the jargon on our sun protection labels, which isn't ideal when we're already a bit sluggish from the heatwave.

For example, six out of 10 people said they were unaware that the SPF rating displayed on labels does not alone guarantee protection from potential sun damage, research form Superdrug found.

Nearly half (44%) of consumers admitted they didn't know what SPF means while one in 10 incorrectly thought the SPF number relates to the minutes they could stay in the sun safely, the poll of 2,000 UK adults also revealed.

But with so many different terms to wade through – UVA, UVB or broad-spectrum protection – it isn’t surprising we’re getting so baffled.

And while skin cancer isn't always preventable, understanding how to protect our skin this summer will help to reduce our chances of it. Thankfully, we spoke to the sun care experts to cut through the jargon so you don’t have to.

Read more: UK weather: What happens to your body when it gets too hot?

What is SPF?

Mother and daughter SPF. (Getty Images)
The SPF rating determines how well you and your loved ones will be protected from the sun. (Getty Images)

This might be the phrase we're most used to seeing, now not just slapped across our suncream labels, but on our moisturisers too.

“SPF stands for sun protection factor and is a measure of how well your sunscreen will protect your skin against UVB rays,” explains Jennie Rickards, clinics manager at The New York Laser Clinic.

SPFs are rated on a scale of two to 50+ based on the level of protection they offer, with 50+ offering the strongest forms of UVB protection, according to the NHS.

“There is a lot of confusion over what the numbers mean on an SPF and which protection factor should be used,” says Rickards.

“The key thing to remember is that on average it takes 10 minutes for your skin, if unprotected, to show signs of burning. Therefore by applying an SPF 30 it will protect it 30x longer, so for 300 minutes."

In other words, the higher the SPF the greater the protection of your sunscreen

But it's important to remember that these figures are just theoretical and in real life, the amount of time you can spend in the sun will also be impacted by other factors like your skin type and the local UV intensity.

Read more: Hot weather: Why you shouldn't sleep naked

What’s the difference between UVB and UVA?

Different types of suncream. (Getty Images)
As well as obvious sun burn, UVB and UVA can cause signs of ageing and wrinkles. (Getty Images)

Now for what the SPF is protecting you against – the two types of sun rays.

“UVB is the main cause of reddening and burning of the epidermis, the skin’s outer most layer,” explains Rickards. ”UVB is superficial and causes the skin to burn, UVA is photo-ageing that penetrates into the dermis layer causing lasting effects to the skin.”

UVA is associated with affecting elastin in the skin, leading to wrinkles and sun-induced skin ageing (for example coarse wrinkles, leathery skin and pigmentation), as well as skin cancer.

Rickards says a good suncream should have a UVA star rating of zero-five, which measures the absorption of UVA rays. It should be at least a four-five star rating for the best protection.

In 2018, a mum issued some advice to other parents to check the UV ratings on their children’s sunscreen and not just the factor.

Taking to social media she explained that there’s much more to sun protection than just simply using SPF.

Instead of just relying on the factor they are using, she too emphasised that parents should also be looking at the star rating on the bottle which relates to its UV protection.

Be aware that if you choose a low SPF it may still have a high level of stars, not because it is providing lots of UVA protection, but because the ratio between the UVA and UVB protection is about the same.

It’s important to choose a high SPF as well as a high UVA protection (e.g. a high number of stars).

Read more: Why do I swell up in the heat? 5 ways to reduce heat oedema this summer

What does broad-spectrum protection mean?

According to Johnson & Johnson and Piz Buin skincare expert Rebecca Bennett, if a sunscreen has broad-spectrum protection it means it has the ability to protect against the harmful effects of both UVA (ageing rays) and UVB (burning rays).

“To be classified as offering broad-spectrum protection, a sunscreen product needs to absorb or reflect at least 90% of the UV rays from the 290 to 400 nanometres (nm) wavelength range,” she adds.

What’s the difference between ‘water-resistant’ and ‘waterproof’?

Woman applying suncream on man. (Getty Images)
Putting on suncream once and jumping straight into the pool won't cut it. (Getty Images)

It’s easy to get the two confused. After all, they basically mean the same thing, right? Not quite.

Current UK tests allow manufacturers to claim a sunscreen is water resistant if the SPF drops by as much as 50% after two 20-minute periods of immersion.

That means if you jump into the pool with SPF30 on, it could drop to SPF15 or less when you get out.

“It's important that your sunscreen is water-resistant when you go swimming because UV radiation half a metre below the surface of water is still 40% as intense as it is on the surface,” explains Bennett.

“You also need to protect the part of your body that's above the surface, as water reflects some 25% of UV radiation and can intensify the harmful effects.”

To be safe, reapply sunscreen after you get out of the pool or water, and don't trust that suncream is entirely 'waterproof'.

Harmful suncream ingredients

While you might think all suncream formulas are created equal, some products contain ingredients that can have detrimental impacts.

“You should watch out for harmful ingredients such as octisalate & octinoxate which only absorbs UVB rays and won't give you full protection,” explains Rickards.

”Your sun protection should include the ingredient zinc oxide as this will cover all rays and is a mineral based ingredient,” she adds.

Read more: How to stay safe in hot weather: Top tips to avoid heatstroke this summer

Sunscreen application and sun behaviour tips

Now you know what the bottles contain, here's how to use them most effectively and stay safe this summer, as per Bennett's advice:

1. Apply sunscreen at least 20 minutes before going out in the sun to allow maximum absorption and protection.

2. Make sure you're applying enough sunscreen. An insufficient quantity lowers the level of protection significantly. Pay special care to more sensitive areas, such as your ears, nose shoulders, cleavage and neck.

3. Don't neglect hard to reach and easily forgotten places, such as your ears, feet and upper back.

4. Re-apply sunscreen every two hours. Apply more frequently after swimming, sweating or towelling.

5. Try to avoid intense midday sun from 11am and 3pm during the summer months or when on holiday in tropical countries.

6. If you are taking medication, check with your doctor or pharmacist to make sure it's OK to spend time in the sun. Some medicines can make the skin more sensitive to the sun's rays.

7. Overexposure to the sun can threaten your health, so avoid staying out in the sun too long, even when using a sunscreen.

8. Protect children. Children are particularly vulnerable to the effects of UV radiation and often spend more time outdoors than adults. Parents should take special care to protect them from the sun using protective clothing, hats, sunglasses and sunscreen. Keep babies and young children out of direct sunlight.

Watch: What is SPF and why is it so important?