Sunscreen is the one step the research is loud about
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The short answer
Does daily sunscreen slow skin ageing?
Yes. In a four and a half year Australian trial of 903 adults, people who used broad-spectrum sunscreen every day showed no detectable increase in skin ageing, and 24% less ageing than those who used it as they liked.
Evidence: Strong How we grade evidence
Most skincare evidence is quiet: small studies, modest effects, lots of “may help”. Sunscreen is different. The evidence is large, long and consistent, and it points one way.
What did the biggest trial of sunscreen and skin ageing find?
Daily sunscreen slowed visible skin ageing in the best trial on the question. The study people keep coming back to is an Australian trial that followed around nine hundred adults for four and a half years, published in the Annals of Internal Medicine in 2013. Half were asked to apply broad-spectrum sunscreen every day, half to use it as they normally would. When researchers compared skin casts at the end, the daily group showed no detectable increase in visible skin ageing over the period, while the as-you-like group did. That is a rare thing in cosmetic science: a proper randomised trial with a result you can see.
Why does sunlight make skin look older?
Sunlight makes skin look older because ultraviolet light breaks down collagen and elastin, the fibres that keep skin looking firm and even. The British Association of Dermatologists' sunscreen fact sheet notes that both UVA and UVB rays are linked to skin ageing, and a 2025 review of UV and photoageing describes UVA reaching deep into the skin and degrading collagen. Cumulative exposure is one of the biggest drivers of how aged skin looks. Blocking it does more for the future look of your skin than any serum can.
How do you choose a sunscreen you will actually wear?
The right sunscreen is a broad-spectrum SPF 30 or above in a texture you like enough to put on every morning.
Broad-spectrum, SPF 30 or above. In the UK look for the UVA circle logo or a UVA star rating of at least 4 stars alongside the SPF number, as the NHS sun safety advice recommends. SPF only tells you about UVB. UVA is linked to skin ageing and still reaches you on cloudy days.
Texture beats numbers. An SPF 50 you hate and skip does less than an SPF 30 you put on every morning. If it pills, stings your eyes or leaves a cast you dislike, change it. Korean and Japanese formulas are popular for exactly this reason.
Enough of it. Most people do not apply enough, and the NHS says that when sunscreen goes on too thinly the protection it gives is reduced. A study of application thickness found that protection from high-SPF products drops off steeply when they are spread thin. Two fingers’ length is a decent visual guide for the face.
Mineral or chemical filters. Both work. Mineral (zinc oxide, titanium dioxide) suits people who react to chemical filters; chemical filters are usually lighter. Neither is “safer” in a way the evidence supports.
Where does sunscreen go in a skincare routine?
Sunscreen goes on last, every morning, after moisturiser and before make-up. Every MyAgenix morning routine ends with an SPF for this reason, and a MyAgenix read shows where it sits in yours. If your budget only stretches to one product, this is the one.
Questions people ask
Do you need sunscreen on cloudy days in the UK?
Often, yes. You can burn in the UK even when it is cloudy, and the NHS suggests protecting your skin whenever the UV index is moderate or higher. Checking the UV index on a weather app is the easiest way to decide.
Is SPF 50 much better than SPF 30?
Only slightly, when both are applied properly. The bigger difference comes from how much you use and how often you reapply, so an SPF 30 you wear generously every day protects better than an SPF 50 you skip or spread thinly.
Does make-up with SPF count as sunscreen?
Not on its own. Hardly anyone applies foundation or powder thickly enough to get the SPF on the label, and some products with SPF only protect against UVB. Wear a proper broad-spectrum sunscreen underneath and treat SPF in make-up as a bonus.
How often should you reapply sunscreen?
Reapply it generously and often when you are outdoors, and always after swimming, sweating or towel drying, even if the label says water resistant. On a day spent mostly indoors, a generous morning application is a reasonable baseline.
Do you need to wear sunscreen in winter in the UK?
Mostly not. The British Association of Dermatologists says year-round sunscreen is unnecessary in the UK for most people, because the UV index in winter months does not get high enough for it to help. Many still wear it daily out of habit, which does no harm.
Sources
- an Australian trial that followed around nine hundred adults for four and a half years (pubmed.ncbi.nlm.nih.gov)
- British Association of Dermatologists' sunscreen fact sheet (skinhealthinfo.org.uk)
- a 2025 review of UV and photoageing (pubmed.ncbi.nlm.nih.gov)
- NHS sun safety advice (nhs.uk)
- A study of application thickness (pubmed.ncbi.nlm.nih.gov)
Sunscreen claims about skin cancer are medical claims, and we do not make them here. Speak to a pharmacist or your GP about sun safety and skin checks.
General information about skin, not medical advice. MyAgenix offers cosmetic guidance to help you choose products. It does not diagnose or treat any condition. For anything that needs treating, see a pharmacist, your GP or a dermatologist.