SPF, UVA, UVB: sun cream explained and how to buy the best

Protecting your skin with an effective sun cream will reduce your exposure to UV rays and ultimately lower the risk of skin cancer and sun damage, but many people don't use enough, and some products don't protect in the way they claim to.

In our expert guide, we explain how sun creams work and how often you need to apply them to be fully protected, plus which ones you can really rely on.

Picking the right type of sunscreen for you is also important. We explain what you need to know about 'once a day' sun creams, water-resistant sun creams, sensitive sun screen and the best kids sun cream too.

To see how popular branded sun creams fared in our tests, including the cheap supermarket versions that passed with flying colours, see our top picks below or the full selection in our sun cream reviews.

Best sun creams

Our independent sun cream reviews identify the products that pass British Standard tests for UVA and UVB sun protection and are easy and pleasant to apply. Products that meet all these criteria are named Best Buys. These are our top picks:

Sun creams to avoid

Shockingly, our sun screen tests uncovered several sun creams that failed UVA or UVB tests, meaning they didn't provide the protection they claimed to – including some high-SPF kids sun lotion. These are the ones to steer clear of:

To see the full list of sun creams tested, head to our sun cream reviews.

SPF, UVA and UVB ratings explained

What does SPF mean?

The sun protection factor (SPF) gives an indication of the amount of protection sun creams offer against UVB radiation. It tells you how much longer skin that's covered with the sun cream takes to redden in response to UV, compared with unprotected skin.

What factor sun cream should I use?

The NHS and Cancer Research UK both recommend you pick a product with an SPF of at least 15, while the British Association of Dermatologists suggests we opt for at least SPF30. If your skin burns easily, it's best to stay on the safe side and opt for a higher SPF.

What are UVA and UVB?

UVA (ultraviolet A) is a type of ultraviolet radiation from the sun, which has been linked with premature ageing. Both UVA and UVB have been linked with skin cancer.

UVB (ultraviolet B) is another type of radiation from the sun and is the main cause of sunburn. It has a shorter wavelength than UVA.

What does the UVA seal mean?

The UVA seal indicates that a product meets the EU recommendation for sun creams to offer a UVA protection factor equivalent to at least a third of their SPF. 

However, some products display the Boots star rating for UVA instead– the protection claimed by these products is higher than the minimum required by the EU.

How does sun cream work? Chemical vs physical sun screen

There are two types of active ingredients in sun creams – physical blockers and chemical absorbers. Chemical absorbers soak up UVA and UVB radiation, while physical blockers act as a screen to protect the skin. Many products use combinations of the two.

‘Organic’ or ‘natural’ sunscreens often use physical blockers only, such as titanium dioxide or zinc oxide, to stop UV rays from reaching the skin. 

Physical blockers are made using naturally occurring minerals. If you do pick a natural product, it’s important to check that it definitely includes an ingredient that acts as a sun filter. 

These types of products can leave more of a white cast on skin, as they don't tend to be absorbed as easily.

How to use sun cream

The UV index gives a good indication of whether you need to apply sunscreen on any given day. The index ranges from low (a rating of one or two), to very high (eight and over). If the index is three or greater, it's worth considering using sunscreen – particularly if you burn easily.

See also: Met Office UV index forecast

How often do I need to apply sun cream?

It’s best to first apply sun cream 15 minutes before you head outside. Experts recommend that you then reapply it every two hours, but you may need to reapply it sooner than this if you go swimming or find yourself sweating a lot.

How much sun cream should I apply?

It’s very unlikely you’re applying too much. The World Health Organization (WHO) recommends 35ml for the total body – that’s around seven teaspoons' worth: one for the face/head and neck, one for each arm and each leg, and one each for your front and your back.

The image above shows the average amount of sunscreen we typically apply in a single full-body application in the hand on the left. Next to this – in two hands – is the amount we should be applying.

Not applying enough sun cream reduces the level of protection you'll receive. According to the WHO, applying a smaller quantity of sun cream leads to a disproportionate reduction in protection – if the quantity applied is reduced by half, protection may fall by as much as two thirds.

Does sun cream go out of date, and can you use it after it's expired?

Yes. Before using a sun cream, check the bottle for a 'period after opening' symbol. This will tell you how long it can be used after opening.

Storing sun cream at high temperatures or in direct sunlight can decrease its shelf life. So if you took last year's sun cream to the beach with you, it's probably time to buy a new bottle.

Types of sun cream

There are a wide range of different formulations available – from oils, lotions and creams to ultra-fine misting sprays, roll-ons and pastes.

Fine sprays can be light, quick and less messy to apply, but aren't great on a windy beach where they are easily blown away.

Some kids options are brightly coloured to make it easier to see if you've missed a spot.

Ultimately what's right for you will depend on your skin type, situation and preferences. Consider where and how you will be using the product and on whose skin, to get the right formulation for you.

Sun cream claims to watch out for

Once-a-day sun creams

A number of products claim to provide sun protection for up to 10 hours after a single application. However, when we tested once-a-day sun creams to see if they really did last all day, we uncovered some worrying results.

In 2016, we conducted our own tests on several once-a-day sun creams, testing their sun protection claims after initial application and again after a day's wear.

We saw an average 74% decrease in SPF protection at the end of the tests. We shared our concerns with Cancer Research UK (CRUK) and the British Association of Dermatologists (BAD). Both advise against relying on any sun cream for extended periods in the sun.  

[add graphic in from this page showing drop in SPF]

At Which?, we don’t think ‘once-a-day,’ ‘eight-hour’ or similar single-use claims should be made on sun creams in the UK (they are banned in other countries, such as Australia), as they may give a false sense of security, and normal daily or holiday activities such as swimming, sweating and clothes rubbing can cause these products to rub off and reduce protection. 

Even with our test subjects just sitting on a chair in a T-shirt, we saw substantial reductions in the level of sun protection, so we don't think you can rely on once-a-day sun cream to keep you protected all day.

Since 2018, the Cosmetic, Toiletry and Perfumery Association (CTPA) has brought out guidance encouraging a shift from once-a-day claims to 'durable' sun cream, with more guidance given on when reapplication is necessary, but we're still seeing plenty of claims that are similar to 'once-a-day'.

Water-resistant sun creams

It's common for sun creams to claim to be 'water resistant', but this doesn't mean that they're waterproof. 

The industry guideline for water-resistant sun creams allows the SPF of a product to drop by 50% after a total of 40 minutes in water. Water-resistance testing also takes place in what is essentially a bath – using tap water. 

We tested two popular sun creams in chlorinated water (to mimic a swimming pool) and salty water (to emulate the sea). We also added another scenario using fast-moving tap water to see what effect this had. Most of the time, the products weren't as effective in our more realistic conditions as they were in tap water.

If you're using sun cream at the beach, apply it copiously before swimming, and again when you leave the water.

Kids sun cream

Babies less than six months old should be kept out of direct sunlight, according to the NHS, and the skin of young children should be protected from the sun when UV levels are high. 

When little ones are exposed to the sun, it’s best to apply a sun protection cream that’s specifically formulated for youngsters and with a high protection factor. Sun creams designed for children and babies are less likely to irritate young skin.

When choosing sun cream for your child, look for a short ingredients list and the terms 'fragrance free' and 'hypoallergenic'. The WHO recommends 35ml of sun cream (seven teaspoons' worth) to cover an adult, so use around a quarter to a half of this depending on the size of your child.

Remember, sun cream is just one part of staying safe in the sun and it's also really important to encourage kids (and adults) to:

• Cover up with loose clothing.
• Wear a hat and sunglasses.
• Avoid the hottest part of the day and seek shade. 
• Keep hydrated.

Learn more in our guide to baby and child sun creams, where you can also see which kids sun creams passed our tests – and the ones that failed.

Sun cream for sensitive skin

Sensitive sun creams tend to use physical blockers, which act as a screen to protect the skin, rather than chemical absorbers, which soak up UV radiation but are also more likely to cause skin irritation.

There’s a long list of ingredients that are used as chemical absorbers, so it’s easiest to simply look for products that are labelled ‘sensitive’ rather than search for specific ingredients.

SPF make-up: does it really offer protection from the sun?

For any product to provide the SPF it claims, you need to apply 2mg per sq cm – which means around a teaspoonful of product needs to be applied to your face. And, just as with sun cream, it needs to be reapplied regularly.

In reality, you’re unlikely to apply the amount of make-up required – in the case of foundation, that would mean a 30ml bottle would only last six applications. When used realistically, make-up isn’t going to protect you from the sun on its own.

Vitamin D deficiency and sun cream

Vitamin D is essential for bone health and also helps keep your teeth healthy. The main sources are sunlight exposure and diet.

During summer, everyday casual exposure is adequate – the WHO advises five to 15 minutes in the summer sun, two or three times a week. Most of us will naturally spend longer than this in the sun during the summer, so it’s still important to use sun cream.

Certain groups are at a higher risk than others from lack of vitamin D, including:

• people with naturally dark skin
• people who wear concealing clothing
• people over 65 years old
• pregnant and breastfeeding women
• people who are confined inside for long periods of time
• people who are overweight.

Some people worry that using sun cream might prevent them from getting enough vitamin D, but this isn’t the case unless you really overdo it. 

From April to September, when the UV Index is generally higher, it takes 10 to 15 minutes of sun exposure each day for those with fair-to-olive skin to get enough vitamin D. 

It takes longer for those with darker skin that rarely burns – it can take 25-40 minutes for the darkest skin type. 

For more details on the importance of vitamin D and where to buy supplements, see our in-depth vitamin D guide.

Other ways to stay safe in the sun

• Consider the time of day – If you're spending time in the sun without wearing sun cream, you should only do so before 11am or after 3pm, as the middle of the day is when you're at the greatest risk of getting burnt.
• Cover up – wear sunglasses to protect your eyes and grab a hat if you need to keep your face out of the sun. You might also want to wear a T-shirt, which can help to cover up typically over-exposed areas such as shoulders.
• Drink plenty of water –make sure you drink regularly on a sunny day. Doing so can relieve headaches and help to heal sunburn, as drinking hydrates your body.
• Know how to treat sunburn – NHS advice says that most cases of sunburn will heal within a week. Get out of the sun, cool yourself with a shower or a damp towel and apply some aftersun, moisturiser or aloe vera gel. You can take painkillers to deal with any discomfort. The NHS also recommends avoiding using ice, popping blisters or wearing tight clothing – or any further sun exposure – while healing. If you feel very unwell, or your child has sunburn, you should talk to your GP or NHS 111. See the NHS sunburn advice page for more.

Where to buy sun cream

You can buy sun cream in pharmacies, supermarkets and discount stores, with some of our tested options coming from Asda, Boots, Garnier, Nivea and Wilko.

Shopping online means you'll have a wider variety of sun creams to choose from, but shopping in-store means you can examine the labels up close to make sure the product is suitable. You might also be able to test the consistency and texture of the sun cream.