SPF stands for Sun Protection Factor. It's a measure of how effectively a sunscreen shields your skin from UVB radiation - the rays responsible for sunburn and a key driver of skin cancer.

But the SPF number isn't a time multiplier. It's a measure of protection level. SPF 30, for example, blocks approximately 97% of UVB rays when applied correctly. SPF 50 blocks around 98%. That 1% difference sounds small - and it is - but what really determines how well your SPF works is how much you apply and whether you reapply throughout the day.

Sunscreen works by forming a protective layer on the skin that either absorbs UV radiation before it can penetrate (chemical filters) or reflects it away from the surface (mineral filters). More on those differences later.

The Science Behind the Number

The higher the SPF, the smaller the marginal increase in protection — which is why dermatologists consistently recommend SPF 30 as the minimum for everyday use rather than insisting everyone use SPF 100.

One important nuance: the SPF number only tells you about UVB protection. For full coverage, you also need protection against UVA rays - and that's where broad-spectrum formulations come in.

Both UVA and UVB rays cause damage to the skin - but they work differently and require different types of protection.

UVA rays are the silent ageing culprit. They penetrate more deeply into the skin, breaking down collagen and elastin over time - and they're present all year round, even on overcast winter days, even through windows. UVB rays are what cause the burn you feel after a day in the sun.

You need protection from both. That's why broad-spectrum is non-negotiable.

How to spot broad-spectrum on a label:

In the UK and EU, look for the UVA circle logo (a circle with "UVA" inside) - this indicates the product meets the required standard for UVA protection. If it's there alongside an SPF rating, you've got broad-spectrum coverage.

This is the question we get asked most often. And the answer is always the same: yes - even in winter, even when it's cloudy, even when you're working indoors.

Here's why.

Up to 80% of UVA rays penetrate cloud cover. So on a grey November morning in the UK, your skin is still being exposed to radiation that causes photoageing. It's just less obvious because you won't burn. But the cumulative effect of daily unprotected UVA exposure - year after year - is what drives premature fine lines, pigmentation, and loss of firmness.

UVA also penetrates glass. If you sit near a window at work, commute by car, or spend any time where light enters through a window, you're being exposed to UVA. Unlike UVB, UVA passes straight through standard window glass.

The evidence for SPF as an anti-ageing tool is stronger than for almost any ingredient in skincare. A landmark study published in the Annals of Internal Medicine found that people who used SPF daily showed 24% less skin ageing over a 4.5-year period than those who used it only sometimes. No serum, retinol or vitamin C can make that claim.

Bottom line: SPF is not a summer accessory. It's your skin's daily armour.

→ Deep dive: Do I need to wear SPF all year round?

The honest answer: for most people, most of the time, SPF 30 is enough - provided you apply enough of it and reapply regularly.

The real-world difference between SPF 30 and SPF 50 is just 1% more UVB blocked. However, if you're spending extended time in direct sun - hiking, at the beach, on the slopes - SPF 50 gives you that extra buffer.

What matters far more than choosing between SPF 30 and SPF 50 is how much you apply. Studies show most people apply only 25–50% of the recommended amount, which dramatically reduces real-world protection. Applying a full ¾ teaspoon of SPF 30 correctly beats applying a thin layer of SPF 50 every time.

When SPF 50 makes more sense:

• Prolonged outdoor activities
• High-altitude environments (UV intensity increases ~10% every 1,000m)
• Fair or sun-sensitive skin
• Anyone with a history of skin cancer or photosensitivity

Both types of sunscreen are effective and safe - but they work differently and feel different on the skin.

Mineral sunscreens use physical UV filters (zinc oxide and titanium dioxide) that sit on top of the skin and deflect UV rays. They're often recommended for very reactive or sensitive skin, but formulation matters enormously - an outdated mineral formula can feel heavy and leave a white cast, especially on medium to deeper skin tones.

Chemical sunscreens use organic filter molecules that absorb UV radiation and dissipate it as heat. They tend to be lightweight, easier to blend, and more cosmetically wearable - especially for those who layer under makeup or wear SPF daily.

The most important thing isn't which type you choose - it's whether you find it comfortable enough to wear consistently. The best sunscreen is always the one you'll actually use every day.

→ Want to know what makes a sunscreen feel genuinely skin-loving? Read: How Polyglutamic SPF makes your skin so dewy

Serum vs Moisturiser: Which Do You Need?

Getting SPF application right is just as important as picking the right product. Here's exactly how to do it.

Step-by-Step: AM Routine

1. Cleanser — start with a clean base
2. Toner (if using)
3. Treatment serum (Vitamin C, Niacinamide, etc.)
4. Eye treatment (if using)
5. Moisturiser
6. SPF — always your final AM step

SPF goes last in your morning routine. Applying it before your moisturiser means you're diluting the formula and reducing its effectiveness.

How Much to Apply

• Face and neck: ¾ teaspoon, or approximately 3 finger-lengths of product
• Body: a shot glass worth to cover full body exposure

Most people apply far too little. If you're using significantly less than this, you're getting significantly less protection than the label claims.

Reapplication - The Step Most People Skip

Reapply every 2 hours when you're outdoors - and after swimming, sweating, or towel drying.

Reapplying over makeup? The trick is to use a slightly damp beauty blender and gently dab (not rub) SPF on top. This avoids disrupting your base while still ensuring coverage. SPF setting sprays can also help top up throughout the day.

Don't Forget These Areas

• Ears
• Eyelids (use a dedicated eye-safe formula or apply carefully)
• Neck (front and back)
• Hands (often forgotten, age-revealing)
• Hairline and parting

Common Mistakes

• Applying too little - the single biggest SPF mistake
• Skipping SPF on cloudy or cool days
• Relying on SPF in foundation or powder as your only protection
• Not reapplying during extended outdoor time
• Applying SPF before moisturiser

With hundreds of SPF products on the market, here's what actually matters when you're choosing one.

The Non-Negotiables

• Broad-spectrum — protects against both UVA and UVB
• SPF 30 minimum for everyday use
• Finish you like — dewy, matte, satin — doesn't matter which, as long as you wear it
• Non-comedogenic if you're breakout-prone
• Fragrance-free if you have sensitive or reactive skin
• Dermatologically tested

Ingredients to Look For

Beyond the UV filters themselves, great sunscreens include additional skin-supporting ingredients that turn your SPF into a multi-tasking step:

Ingredients to Be Mindful Of (for sensitive skin)

• Fragrance / parfum - a common irritant
• High alcohol content — can dehydrate skin over time
• Oxybenzone - restricted in the EU/UK

Sunscreen Textures - What to Expect

SPF is for everyone - but not every formulation is right for everyone. Here's what to look for based on your skin type.

A note on SPF and skin tone: SPF is essential for every skin tone. Whilst people with more melanin in their skin have some natural UV protection, it is not sufficient to prevent long-term UV damage, photoageing, or hyperpigmentation. Darker skin tones are also more prone to certain UV-triggered pigmentation concerns, making broad-spectrum SPF an important daily step for everyone.

→ More information: Sunscreen for sensitive skin

Common Myths - Debunked

"I don't need SPF on cloudy days."
FALSE. Up to 80% of UVA rays penetrate cloud cover. Your skin can't feel UVA — but that doesn't mean the damage isn't happening.

"My foundation has SPF, so I'm covered."
FALSE. The SPF in most foundations is minimal (usually SPF 15), and most people don't apply nearly enough foundation to achieve even that. Foundation SPF is a bonus, not a replacement.

"People with darker skin tones don't need SPF."
FALSE. All skin tones are susceptible to UV damage, premature ageing, and UV-triggered hyperpigmentation. SPF is non-discriminatory.

"SPF causes breakouts."
Mostly false. Breakouts are usually caused by a specific formulation - not SPF itself. Non-comedogenic, lightweight formulas are designed for acne-prone skin and won't clog pores.

"Mineral SPF is always safer or better for sensitive skin."
Not necessarily. What matters most is the overall formulation - a well-formulated chemical sunscreen can be perfectly suitable for sensitive skin.

"I only need SPF in summer."
FALSE. UVA is present year-round. UVB also remains active at levels capable of causing damage even in UK winters. Daily SPF every day of the year is the gold standard.

Potential Side Effects - and What Causes Them

Who Can Use SPF?

SPF is safe for virtually everyone:

• All skin types
• Sensitive skin conditions (rosacea, eczema) - patch test first
• Pregnancy and breastfeeding
• Teenagers and under 12s
• All skin tones

Always patch test when introducing a new SPF product — apply a small amount to the inner forearm and wait 24 hours before full-face application. → Learn why: Why do I need to do a patch test?

On application:

• Always apply SPF as your final AM skincare step - after moisturiser, never before
• Apply to slightly dry skin (unlike hyaluronic acid, SPF doesn't need a damp base)
• Use gentle pressing motions rather than rubbing to ensure even coverage
• Give it 2–3 minutes to absorb before applying makeup for the smoothest finish

On layering:

• Pair SPF with Vitamin C in your morning routine for enhanced antioxidant + UV protection - they work synergistically
• If your SPF feels heavy, try switching to a lighter formula rather than applying less - application amount is critical
• Hyaluronic Acid or Polyglutamic Acid serums underneath SPF boost comfort without affecting protection

On reapplication:

• Set a reminder on your phone if you're outdoors for an extended period
• Keep a travel-size SPF in your bag for midday top-ups
• Don't use last year's SPF - check the PAO (period after opening) symbol and expiry date

On lifestyle:

• The most evidence-backed anti-ageing step is consistent daily SPF - more so than retinol, peptides, or any serum
• If you've never found an SPF you love wearing, the issue is the formula - not SPF itself. Keep trying. The right one exists for you.

Morning Routine - Full Sequence

Evening Routine - Removing SPF Properly

SPF removal is as important as SPF application. Chemical filters in particular are designed to bond to skin - they won't fully remove with water alone.

1. Step 1 — Oil or balm cleanser: Emulsifies and dissolves SPF and makeup. This is the non-negotiable first step.
2. Step 2 — Water-based cleanser: Removes residue and leaves skin clean.
3. Then continue with your evening routine as normal.

→ Our Oat Cleansing Balm melts makeup and SPF in 30 seconds.

Ingredients That Work Beautifully Alongside SPF

Want to understand exactly how Vitamin C works and how to get the most from it in your morning routine? Read our complete Vitamin C guide.

Using retinol in your evening routine? SPF the next morning is non-negotiable - retinol increases your skin's sensitivity to UV. Visit our complete Retinol ingredient guide for everything you need to know about building retinol into your routine safely.

What Doesn't Belong in Your AM Routine

Some ingredients are best saved for evenings when SPF is on board:

• Retinol — photosensitising; use PM only
• AHAs / BHAs — can increase UV sensitivity; use PM and always pair with AM SPF

Dewy Sunscreen SPF 30 - £15 | 50ml

Your daily hydration and protection essential. SPF 30 sunscreen that delivers instant and lasting hydration whilst shielding from UV damage, leaving skin with a natural dewy finish. Broad-spectrum UVA & UVB protection powered by an 8% hydration trio of Polyglutamic Acid, Glycerin and Squalane.

• Broad-spectrum SPF 30 UVA & UVB
• 8% Polyglutamic Acid, Glycerin & Squalane hydration trio
• Lightweight, non-greasy, dewy finish
• 97% said it looked invisible on their skin tone*
• Suitable for all skin types, including sensitive skin
• Pregnancy and breastfeeding safe
• Fragrance-free | Non-comedogenic | Dermatologically tested

*Based on a 2-week independent consumer trial of 66 people

Shop now

Everything you need to go deeper on sun protection:

Do I Need to Wear SPF All Year Round?

Year-round UV exposure and why daily SPF matters in every season

Sunscreen for Sensitive Skin

How to find an SPF that works for reactive, sensitive, or redness-prone skin

How Polyglutamic SPF Makes Your Skin So Dewy

The ingredient behind a truly skin-loving sunscreen texture

Introducing: Dewy Sunscreen SPF 30

Everything about our lightweight, hydrating, dewy-finish SPF 30