There’s a particular British attitude to sunscreen: it comes out of the cupboard for holidays and heatwaves, and goes back in for the other eleven months. It’s understandable — it’s grey here a lot — and it’s the single biggest gap in most people’s skincare.

The damage that ages skin isn’t mostly from the two weeks in Spain. It’s from the accumulated hours: the walk to the station, the drive to work, sitting near a window, twenty minutes in the garden in April. None of it feels like sun exposure. All of it counts.

UVA and UVB, and why the difference matters here

UVB causes sunburn. It’s strongest in summer, around midday, and it’s largely blocked by glass. The SPF number on a bottle describes protection against UVB and nothing else.

UVA penetrates deeper into the skin, causes the collagen breakdown behind photoageing, and contributes to skin cancer risk. Crucially, UVA levels stay relatively consistent through the day and through the year, and UVA passes through cloud and window glass.

So a grey January morning in Manchester still delivers UVA. You won’t burn. Your skin is still ageing.

This is why SPF alone is an incomplete measure. In the UK and EU, look for the UVA logo — the letters UVA inside a circle — which means the UVA protection is at least a third of the SPF value. Some products also carry a star rating from 0 to 5; four or five stars is what you want.

A bottle with SPF 50 and no UVA logo is telling you about half the story.

How much to actually apply

The tested SPF figure assumes 2mg of product per square centimetre of skin. In practice most people apply somewhere between a quarter and a half of that, and protection drops disproportionately — not linearly.

For the face and neck, the commonly cited amount is roughly a third to half a teaspoon, or the “two finger” method: a strip of product along the length of your index and middle fingers.

It’s more than looks reasonable. It’s supposed to be.

For the body, around 35ml — roughly a shot glass — for a full application in a swimsuit.

Practical fix: apply, wait two minutes, apply again. Two thin layers get you closer to the tested amount than one careful one, and it’s easier than trying to spread a visibly large blob.

Which SPF number

SPF 30 blocks around 97% of UVB. SPF 50 blocks around 98%. The difference is small on paper.

It matters more in practice, though, because nobody applies enough. If you’re applying half the tested amount, starting from SPF 50 leaves you better protected than starting from SPF 30.

SPF 30 minimum for daily use, SPF 50 if you’re outdoors for extended periods, have fair skin, are on photosensitising medication, or are using retinoids and acids.

Mineral or chemical

Mineral (zinc oxide, titanium dioxide) sits on the surface and reflects and scatters UV. Effective immediately on application. Generally better tolerated by sensitive and rosacea-prone skin. Can leave a white cast, which is worse on deeper skin tones — though modern tinted formulations have improved this considerably.

Chemical (avobenzone, octocrylene, and newer filters) absorb UV and convert it to heat. Cosmetically elegant, no white cast, and generally the more comfortable option for daily wear. Some filters can sting sensitive eyes.

Neither is meaningfully better. The best sunscreen is the one you’ll actually put on every day, which is a genuine consideration rather than a platitude.

Worth knowing: European and UK-available sunscreens have access to a broader range of modern UV filters than US products do, which is why the texture and UVA protection of European formulations is often better.

Reapplication in real life

Every two hours of continued sun exposure. After swimming, heavy sweating, or towelling.

But — and this is where the standard advice becomes unhelpful — if you’re indoors all day, away from windows, you don’t need to reapply hourly. The two-hour rule is for ongoing exposure.

Sensible defaults: apply properly in the morning. Reapply before going out at lunchtime. Reapply if you’re outside for any length of time. Don’t worry about it if you’ve been at a desk in an internal office.

The practical problem of reapplying over makeup has its own answer — see how to reapply sunscreen over makeup.

What doesn’t count as sun protection

The SPF in your foundation. The amount of foundation people apply is a small fraction of the tested quantity, so the actual protection is a small fraction of the stated number. The full explanation is in SPF makeup — it is not a substitute for sunscreen.

The SPF in your moisturiser, if you apply moisturiser sparingly. Better than nothing, not adequate on its own.

Last year’s bottle, if it’s past its expiry or has been sitting in a hot car.

Being in the shade. UV reflects off surfaces — water, sand, and snow substantially so.

Being in a car. Windscreens block most UVA; side windows generally don’t. Drivers in the UK often show more photoageing on the right side of the face.

The vitamin D question

A fair concern, and worth addressing rather than dismissing.

Vitamin D deficiency is genuinely common in the UK. From about October to March, the sun in Britain isn’t high enough in the sky for the skin to produce meaningful vitamin D regardless of what you do — which means winter sun exposure isn’t buying you any anyway.

NHS advice is to consider a daily 10 microgram (400 IU) supplement through autumn and winter, and year-round for people who are rarely outdoors or who have darker skin.

The sensible position: take the supplement, wear the sunscreen. Deliberately unprotected sun exposure is a poor way to obtain a nutrient available in a tablet.

Beyond sunscreen

Sunscreen is one layer, and it’s the one most likely to be applied inadequately.

Clothing is the most reliable barrier, and fabrics vary enormously — the detail is in sun protection clothing and UPF ratings.

A wide-brimmed hat protects the areas people most often miss: ears, hairline, the back of the neck.

Sunglasses protect the eyes and the thin skin around them, and reduce squinting.

Shade and timing. UV is strongest between 11am and 3pm in the UK summer.

The UV index

Worth learning to read, because it removes the guesswork.

The Met Office publishes a UV index forecast. Below 3, minimal protection is needed for most people. From 3 upwards, protection is worth it.

In the UK the index typically reaches 3 or above from around April to September, peaking at 7 or 8 in high summer — occasionally higher. It can reach 3 on an overcast day, which is exactly the situation people misjudge.

Areas people miss

Ears, particularly the tops. The back and sides of the neck. The chest and décolletage, which shows photoageing early and severely. The backs of the hands, which age faster than the face for exactly this reason. Eyelids. The scalp parting, especially with thinning hair. Lips, which need an SPF balm. And feet, in summer.

Check your skin

This section matters more than the rest of the article combined.

See a GP promptly about any mole or patch of skin that is asymmetrical, has an irregular border, has more than one colour, is larger than 6mm, or is changing in size, shape, colour or sensation. Also anything that itches, bleeds, crusts, or doesn’t heal within a few weeks.

Skin cancer is common in the UK and highly treatable when caught early. Get anything you’re unsure about looked at — GPs would far rather see ten harmless moles than miss one that mattered.

This article is general information, not medical advice. Any new, changing, bleeding or non-healing skin lesion should be assessed by a GP without delay.