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The ultimate guide to SPF: how to protect your skin
Written byNatalie Beastall
Reviewed byHeeral Patel
Is your sunscreen truly up to the task? The sun’s rays can do more damage than you think – let’s break down the difference between UVA, UVB as well as SPF
Summary
1SPF: the lowdown
SPF is your sunscreen rating and tells you how much protection you’re getting against UVA rays…
2How does SPF work?
It creates a shield that helps block the sun’s UVA and UVB rays, which helps prevent damage to your…
3What does the SPF number mean?
The number tells you how long it’ll help protect your skin. So, SPF 30 (when applied correctly) gives…
We all know we’re supposed to wear sunscreen, but how exactly does it work? And what’s the deal with all those acronyms: UVA, UVB and SPF? Turns out, the sun can sneak up on you even when it’s not scorching hot, and different types of UV rays need different kinds of protection.
Let’s jet off into the world of sunscreen and find out what those labels really mean and how to stay safe and glowing all year long.
What is SPF?
SPF is your sunscreen rating, it tells you how much protection you’re getting against the UVB rays. The higher the SPF number, the more protection it offers.1
How does SPF work on your skin?
SPF works like your skin’s personal bodyguard, creating a shield that blocks the sun's harmful UVA and UVB rays from doing any damage.
Some sunscreens use physical blockers, like zinc oxide or titanium dioxide, which act like tiny mirrors, reflecting UV rays away from your skin2 – think of it as a shiny force field. Mineral sunscreens sit on top of your skin and keep those rays at bay.
On the other hand, chemical sunscreens go to work by absorbing UV light.3 They contain ingredients like avobenzone or oxybenzone, which soak up the rays, preventing them from penetrating and causing damage. As these chemicals absorb UV rays, they break them down and release a little heat in the process – kind of like turning bad energy into harmless warmth.
Some sunscreens combine both methods, giving you the best of both worlds: reflection and absorption, keeping your skin sun-safe and sound all day long.
What does the number mean on SPF?
Here’s the scoop: the number on your sunscreen bottle tells you how long you can stay protected in the sun, compared to not wearing any at all (please don’t do this). For example, an SPF30 generally means it would take you 30 times longer to burn4 than if you didn’t wear any SPF at all. So in theory, SPF30 (when applied correctly) can give you twice the protection of SPF15.
No sunscreen can block out UV rays entirely, but ultimately, the higher the SPF number, the better the protection. In fact, it’s thought that SPF30 blocks about 97% of UVB rays, while SPF50 blocks about 98%.3
When you’re choosing your sunscreen, keep in mind the different SPF tiers5 as a guide to how much sun protection you’ll be getting:
- low protection (SPF4, 6, 8 and 10)
- medium protection (SPF15, 20 and 25)
- high protection (SPF30, 40 and 50)
- very high protection (SPF50+)
Can you still burn while wearing sunscreen?
Here’s the catch – we all sweat, miss bits or forget to top up our sunscreen during the day. So even if you do wear SPF out in the sun, you could still get sunburned.
To help stop this, the NHS1 recommends you:
- spend time in the shade when the sun is at its strongest
- wear sunglasses to protect your eyes
- reapply your sunscreen every two hours
- wear water-resistant sunscreen if you’re going swimming (and reapply straight after)
- wear a hat to protect your face and scalp
What is UVA?
UVA is pretty sneaky, it makes up about 95% of all UV rays that hit your skin from the sun.6 And guess what? It’s not just around when the sun’s shining; it can still reach you through clouds.7
You’ll also find it lurking in sunbeds, sunlamps and tanning booths, and could even be more dangerous8 depending on:
- the strength of the UV rays
- how often you hit the tanning booth
- how long you spend in there
- your skin type and colour
- your age
UVA rays go deep beneath the surface, messing with your skin’s elastin, which means they’re the main culprits behind those unwanted signs of ageing like wrinkles, fine lines and sagging.9
So, next time you think about skipping the SPF (don’t!) or heading to the tanning shop (also maybe don’t). Sunbeds have a strong link to skin cancer, as the UV radiation damages the DNA in your skin cells.8 So remember: it’s not just about looking good today, but keeping that youthful glow for the long haul.
What is UVB?
UVB makes up the rest of the UV rays that reach us from the sun. These rays don’t dig as deep as UVA but can still harm our skin.10
UVB is the main culprit for sunburn and just like UVA, UVB can damage your skin.6 In fact, UVB are the biggest offenders when it comes to DNA damage, which can increase the risk of skin cancer.6 But, it’s important to remember that both UVA and UVB can cause damage.
Which SPF should I use?
Choosing the right SPF can be a bit confusing with so many options around. But it’s important to pick one that suits your skin type and gives you proper protection. Here’s a quick guide to help you out:
Don’t let your sunscreen add to the grease. Instead, look for lightweight, oil-free products that won’t clog your pores or leave your skin feeling like an oily mess. High SPF sunscreens can sometimes feel thick and sticky – definitely not what you want if you’re prone to oily skin.
What to go for: oil-free, lightweight creams, gels and mineral powders that keep things fresh and shine-free.
If your skin is sensitive, you need a sunscreen that’s gentle and free from irritating ingredients like alcohol, essential oils and has been dermatologically tested to make sure it’s suitable for sensitive skin types. These can cause flare-ups, especially if your skin’s already a bit temperamental. If you’re super sensitive, mineral powder sunscreen could be your best bet – but remember to reapply regularly.
What to go for: products tested to suit sensitive skin types that are lightweight, fragrance-free, mineral powder sunscreens with minimal ingredients that won’t upset your skin.
Opt for a lightweight, hydrating SPF that does double duty as a moisturiser. It’ll keep your skin plump and nourished while protecting it from the sun – two birds, one stone.
What to go for: hydrating sunscreens that moisturise while keeping your skin safe from the sun’s rays.
For those with combination skin, you want something that gives the right balance – lightweight, not too greasy but still hydrating where you need it. No one wants an SPF that feels heavy on your skin or clogs your pores.
What to go for: SPF gels that are light on your skin but still provide the moisture you need, without overdoing it.
Don't forget your delicate eye area and lips. There are special sunscreens for these spots, but they can sometimes be a bit low on the SPF scale (around SPF15). So, a gentle layer of regular sunscreen on your face can give you the protection you need.
What to go for: lip balms, eye creams and hand creams with SPF that are specially designed to protect these delicate areas.
Dark skin still needs SPF. While you might have more natural protection, the sun can still cause damage, leading to pigmentation or melasma. Make sure to use at least SPF30 to keep your skin safe.
What to go for: SPF30 or higher, well-absorbing formulas – perhaps a tinted sunscreen that suits your skin tone.
If you have pale skin, you’ll need a high SPF (ideally SPF50) because you’re more likely to burn.1 Choose between mineral or chemical sunscreens to keep your skin protected all day long.
What to go for: High SPF (50+), mineral or chemical sunscreens that offer serious protection for pale skin.
Whatever your skin type, choosing the right SPF is the key to happy skin. So pick wisely and protect yourself from those pesky sun rays.
How to apply SPF
If you’re going to have a lot of your skin exposed to the sun, then you’ll need at least six to eight teaspoons of sunscreen for your entire body.1
Be sure to apply your SPF last, so after you’ve used any serums or moisturiser. If it’s a mineral sunscreen you should be good to go out in the sun straight away, but if it’s a chemical one you’ll have to wait 15-30 minutes for it to sink in.
- try not to mix your own SPF/moisturiser or make-up as this will affect the efficacy of the product11
- always wear SPF if you use retinol,12 benzoyl peroxide13 and AHA/BHA acids14
- it's important to only use retinol at night too, as it's an active ingredient which may increase skin sensitivity to the sun14
Do you need to wear sunscreen in the winter?
The short answer is yes. Even if it’s cold outside and summer is long gone, you’re still at risk of burning or UV damage, even on cloudy days. In winter, reflected light from snow, sand and water can also intensify your exposure to UV rays.7
The final say
Now that you’re a sunscreen pro, it’s time to make SPF your best skincare buddy. Whether you're hitting the beach to top up your tan or just popping out for errands, SPF is an important part of every skincare routine. From oily to dry skin, there’s a perfect SPF for everyone and with the right protection, you’ll not only guard against sunburn but keep your skin looking fresh, youthful and healthy.
This article provides informational advice and is not a substitute for medical care. Curated by experts for accuracy, we take great care to ensure the information is up-to-date and relevant. However, you should always consult your GP or healthcare professional before using supplements or alternative products, particularly if you have medical conditions or are under supervision.
1. NHS. Sunscreen and sun safety [Internet]. nhs.uk. 2022. Available from: https://www.nhs.uk/live-well/seasonal-health/sunscreen-and-sun-safety/
2. Smijs T, Pavel S. Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness. Nanotechnology, Science and Applications [Internet]. 2011 Oct 13;4(4):95–112. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3781714/
3. Gabros S, Zito PM. Sunscreens And Photoprotection [Internet]. Nih.gov. StatPearls Publishing; 2019. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537164/
4. The Skin Cancer Foundation. The Skin Cancer Foundation; 2022. Available from: https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/
5. Lergenmuller S, Ghiasvand R, Robsahm TE, Green AC, Lund E, Rueegg CS, et al. Sunscreens With High Versus Low Sun Protection Factor and Cutaneous Squamous Cell Carcinoma Risk: A Population-Based Cohort Study. American Journal of Epidemiology. 2021 Aug 11;
6. Cancer Research UK. How does the sun and UV cause cancer? [Internet]. Cancer Research UK. CRUK; 2021. Available from: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/how-does-the-sun-and-uv-cause-cancer
7. US EPA. Ultraviolet (UV) Radiation and Sun Exposure [Internet]. US EPA. 2018. Available from: https://www.epa.gov/radtown/ultraviolet-uv-radiation-and-sun-exposure
8. Cancer Research UK. How do sunbeds cause skin cancer? [Internet]. Cancer Research UK. CRUK; 2019. Available from: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/how-do-sunbeds-cause-skin-cancer
9. Amaro-Ortiz A, Yan B, D’Orazio J. Ultraviolet Radiation, Aging and the Skin: Prevention of Damage by Topical cAMP Manipulation. Molecules [Internet]. 2014 May 15;19(5):6202–19. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4344124/
10. International Agency for Research on Cancer. Solar and Ultraviolet Radiation [Internet]. www.ncbi.nlm.nih.gov. International Agency for Research on Cancer; 2012. Available from: https://www.ncbi.nlm.nih.gov/books/NBK304366/
11. British Association of Dermatologists [Internet]. Bad.org.uk. 2025. Available from: https://www.bad.org.uk/photographic-evidence-highlights-shortcomings-of-moisturisers-containing-spf/
12. Retinol - an overview | ScienceDirect Topics [Internet]. www.sciencedirect.com. Available from: https://www.sciencedirect.com/topics/medicine-and-dentistry/retinol
13. NHS. About Benzoyl Peroxide [Internet]. nhs.uk. 2022. Available from: https://www.nhs.uk/medicines/benzoyl-peroxide/about-benzoyl-peroxide/
14. Almeman AA. Evaluating the Efficacy and Safety of Alpha-Hydroxy Acids in Dermatological Practice: A Comprehensive Clinical and Legal Review. Clinical, Cosmetic and Investigational Dermatology [Internet]. 2024 Jul 16;17:1661–85. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11268769/
