How does sunscreen work?

It’s the science that keeps us sun safe

You’ve got your beach towel, your sunglasses and a new holiday read – you’re ready to hit the sun. Hold up! Have you got your sunscreen? We all know it's an essential part of staying safe in the sun, but what does it do and how does it work? We’re glad you asked. Stick with us for the A to Z of sunscreen.

Sunscreen 101

Sunscreen helps to shield the skin from immediate and long-term damage caused by exposure to the sun. We all know a lobster-red look is hard to pull off, so it’s really important to make sure you’re kitted out in the sun. Whether it’s a lotion, cream or spray, there’s a type of sunscreen for everyone.

Containing active ingredients that protect you from UVA and UVB rays, suncare products choose from two different classes of UV filters (or sunscreens, hence the name) to stop the sun’s rays damaging your skin. Let’s talk about how they work.

Reflector UV filters work by reflecting and scattering UV rays away from the skin, acting as a kind of mirror. Suncare products for babies and children with a high SPF (we’ll come on to that) often contain reflecting filters.

Absorbing UV filters work by absorbing ultraviolet light much like a sponge soaks up water. Each tiny sunscreen ‘sponge’ soaks up ultraviolet light, and then chops it up into smaller packets of less harmful energy absorbed back onto the skin – clever stuff! Absorber type UV filters tend to be very specific about the type of UV light they absorb so some will only filter UVB rays whilst others will be UVA specific.

So, sunscreen’s main job is to protect the skin from UVA and UVB rays and minimise the damage they can cause to the skin. Certain types of sunscreen can give your skin extra benefits like added moisture, or they contain ingredients like ceramides which can help protect your skin’s natural barrier.


We know wearing sunscreen protects against UVA and UVB rays, but what’s the difference between the two? Lab coats on, it’s time for a bit of science. Sunlight travels to earth in both visible and invisible rays, and many of these are made up of ultraviolet (UV) light.

UVA rays (long-wave UV light) are around whenever there’s daylight – even if the sun’s not shining. As the longest ray on the UV spectrum, they’re able to reach into the inner layer of the skin and can damage skin’s elasticity and firmness, causing premature skin ageing. Unlike UVB rays they can penetrate window glass – so wearing sunscreen all year round is super important.

UVB rays are at their strongest during the summer months, and their strength depends on where you are in the world, the time of day (between 11am and 3pm is when the sun is at its strongest) and the season – for us in the Northern Hemisphere, that means we’ll usually see the strongest UVB rays in June, July and August.

UVB light consists of shorter wavelengths than UVA, but that doesn’t mean it does less damage to your skin. UVB rays are highly energetic, causing immediate skin damage (sunburn to you and me.) They also play a part in a person developing skin cancer and skin ageing.

What is SPF?

If you’ve ever wondered what the letters SPF on the bottle mean, it stands for sun protection factor and is the length of time you’re protected from burning. The higher the level of SPF, the greater the length of time you’ve got protection against burning depending on your skin type. Whilst it’s important that we all wear sunscreen, the SPF needed to protect your skin will vary from person to person – so it’s a good idea to check out which is right for your skin tone. If in doubt, use SPF 50+ with a five star UVA rating. Apply your sunscreen liberally all over your body, that way you’ll get the level of protection on the pack.

Star rating? What's all that about?

The UVA star rating system was developed by Boots in 1992 (we won’t blow our own trumpet any further), and it measures UVA protection. UVA is responsible for deeper damage to your skin that builds up over time. You’ll find a rating of up to five stars on the bottle of your sunscreen – the higher the rating, the more protection you’ll get. Psst! Our entire Soltan range offers 5-star protection, take a look!

Staying smart in the sun

There’s nothing better than a bit of sun, right? It plays an important role in our overall health and mental wellbeing. Whilst we long for blue skies and warm weather, it’s really important to make sunscreen your sunshine partner.

Remember to apply sunscreen before venturing out in the sun, especially on your face as the skin is more exposed than the rest of your body. Always reapply every two hours as sunscreen can rub off and lose its effectivity. If you’ve dipped your toes or dunked your head in the pool, it’s time for a reapply. Even water-resistant sunscreens won’t last forever. Make sure it’s had time to soak in before you splash back into the water.

Children’s skin is more vulnerable than adults as they tend to spend more time outdoors. We know that sun damage builds up over the years so the more exposure you have a child, the greater the risk of longer-term skin damage as you age. It’s best to apply an SPF 30 or higher on your little one’s skin. Children aged under six months should be kept out of direct strong sunlight, and older children should cover up with clothing and wear sunglasses, especially when the sun is at its strongest.

For little ones, check out Soltan Kids Learn to Reapply UV Detection Stickers! Clear when they’re protected, purple when they’re not – the UV detection stickers change colour as their sun cream wears off. One sticker lasts all day, wet or dry.

And now you know the science behind sunscreen! Keep in mind that it’s good to limit your sun exposure by spending time in the shade – sunscreen won’t protect you from things like dehydration or heat stroke.