The ABC of Sunscreen: The NAYA Sunscreen Guide: Every Question Answered

Updated: May 2026  ·  Reading time: approx. 15 minutes  ·  Written by Sarah, Founder of NAYA Skincare

Get a cup of tea. This one is long.

How SPF is determined

In the laboratory, volunteers with different skin types are first assessed to establish how quickly their skin reddens under a calibrated UV lamp. Then 2mg of sunscreen is carefully applied to a measured square centimetre of skin, allowed to settle for fifteen minutes, and the skin is exposed again. The SPF is the ratio of how much longer it takes for redness to appear on protected versus unprotected skin.

One thing worth knowing: products often test higher than the number on the label. The stated SPF is a conservative value — deliberately set lower than the actual test result to account for real-world application, where most people apply less than the 2mg/cm² standard. NAYA Everyday Sun Cream, for example, tests at SPF 60 but is labelled SPF 50+.

Is a higher SPF always better?

Yes — and the claim that SPF 50 is only marginally better than SPF 30 is a myth worth addressing directly.

The difference looks small when expressed as percentage blocked — 96.7% versus 98%. But skin does not experience the percentage blocked. It experiences the UV that still gets through.

SPF 30 allows around 3.3% of UVB to reach the skin, while SPF 50 allows around 2%. That means SPF 50 reduces the UVB dose reaching the skin by roughly 40% compared with SPF 30. Put differently, SPF 30 allows about 65% more UVB through than SPF 50. Over months and years of cumulative exposure, that difference is meaningful. SPF 50 is often the more practical daily choice, particularly because most people apply less than the tested amount.

The practical downside of higher SPF is that formulas can be thicker and harder to wear. This has improved substantially in recent years with modern organic filter technology, which achieves high SPF at lower concentrations and more elegant textures.

UVA protection: what SPF doesn’t tell you

SPF only measures UVB protection. UVA — which penetrates more deeply, passes through glass and cloud, and is present year-round — is responsible for most visible photoageing, pigmentation and long-term skin change. SPF tells you nothing about UVA coverage.

How to check for UVA protection on a label:

• PA rating (PA+ to PA++++) — Asian grading system. PA++++ is the highest tier. NAYA Everyday Sun Cream is PA++++.
• UVA circle logo — EU standard. Confirms UVA protection is at least one-third of the stated SPF value.
• Broad-spectrum — US standard. Confirms some UVA protection but does not specify the level.

If you are managing pigmentation, redness or premature ageing, UVA protection matters as much as SPF — arguably more for daily use. A sunscreen with SPF 50 and PA++++ is a more complete choice than SPF 50 without a UVA rating.

How much sunscreen to apply

The international standard is 2mg per square centimetre of skin. For the face and neck combined, this works out to approximately half a teaspoon — more than most people apply.

Research consistently shows that people apply between 25% and 65% of the required amount. If you apply 0.5mg/cm² to an SPF 15 product, you are receiving approximately SPF 4 in practice. This is why applying the right amount matters more than the SPF number on the label.

For the body: approximately 30ml total (around six teaspoons) for a full body application. Most people use a fraction of this. More is more.

How to apply sunscreen correctly

Sunscreen works best as an even, undisturbed layer. A few principles that make a real difference:

• Apply after skincare, before makeup. Organic filters do not need to absorb into bare skin to work. Apply over your moisturiser or serum once it has settled.
• Spread, don’t rub. Studies show that heavy rubbing reduces protection. Dab the product across different areas of the face first, then spread gently and allow it to settle. Think wet paint — you want an even layer, not an ingredient driven into the skin.
• Allow 15 minutes before going outside. Not because filters need time to activate, but because the film needs time to set and not get wiped off onto clothing or moved around.
• Cover the sun terraces. Forehead, nose, ears, shoulders, back of the neck, tops of feet. These are the areas where light-skin cancer most commonly develops and the areas most often missed.
• Apply before getting dressed when covering body areas, to avoid missing the edges of swimwear or clothing.

Do you need to reapply sunscreen?

Yes — and the reason is worth understanding clearly. Reapplication is not because UV filters degrade and stop working. Modern photostable filters maintain their efficacy well beyond two hours. The reason to reapply is film integrity.

Over time, the sunscreen layer becomes uneven as skin moves, produces sweat and oil, and the product is rubbed by clothing or touch. Tiny gaps form in the protective layer that UV can reach through. Reapplication restores an even film.

The two-hour rule is about time on skin, not time in sun. If you are mostly indoors, a morning application is generally sufficient. If you are outdoors for extended periods or swimming, reapply every two hours or after getting wet.

Products that sit lightly on the skin and do not feel like a burden to reapply make this step dramatically more realistic. This is one of the practical arguments for organic filter formulations.

Sunscreen with skincare and makeup

The order is: skincare → sunscreen → makeup. Give each step a moment to settle before the next.

A few specific questions that come up frequently:

Do I need to wait between skincare and sunscreen?

Allow skincare to settle before applying sunscreen — about 5 minutes is usually enough. This minimises the risk of the sunscreen layer being disrupted by products that have not yet absorbed.

How do I apply makeup on top of sunscreen?

Allow the sunscreen to set for 5–10 minutes before applying makeup. Apply makeup as gently as possible — heavy patting and rubbing will disturb the sunscreen layer. The less you move the sunscreen around, the better the protection remains.

Can I use a tinted moisturiser or SPF foundation instead of sunscreen?

Generally no. The amount you need to apply to get the labelled SPF — half a teaspoon for the face — is far more than most people apply as a tinted product. The result is a fraction of the stated protection.

Balling up, shininess and texture issues

Why does sunscreen ball up?

Usually one of three causes: interaction with an incompatible skincare product underneath, drying too quickly, or rubbing too aggressively. Solutions: try applying on clean skin or on well-moisturised skin, or switch to a gentler patting application. Oily skin can sometimes cause balling through the skin’s own sebum interacting with the formula.

How do I reduce shine from sunscreen?

Most sunscreens contain oil-soluble components, so some shine is expected. The most effective approach without reducing protection is to allow the sunscreen to fully set, then gently pat a starch-based translucent powder on top. Avoid blotting paper, which removes product along with oil.

Can you mix, DIY or substitute sunscreen?

Can I mix sunscreen with foundation or moisturiser?

No. Mixing disrupts the emulsion structure that SPF testing is based on. The result is patchy, unpredictable protection with significantly reduced effective SPF. If you want a tinted sunscreen, choose one formulated that way from the start.

Can I make DIY sunscreen?

No. Effective sunscreen requires precise particle size, distribution and base chemistry that cannot be replicated at home. Even professional formulators with industrial equipment sometimes achieve low SPF results from poorly dispersed zinc oxide. DIY sunscreen recipes are not a safe substitute.

Can I use an SPF moisturiser instead of sunscreen?

Not reliably. The volume required to achieve the labelled SPF is greater than most people apply as a moisturiser. Use a dedicated sunscreen as your final skincare step.

Practical questions

Can I use expired sunscreen?

No. There is no guarantee of efficacy after the expiry date. Also avoid storing sunscreen in hot conditions — a car glovebox, direct sun at the beach — as heat can break down the emulsion and reduce protection before the expiry date is reached.

Do I need sunscreen indoors?

For most people in most rooms, a single morning application is sufficient. Window glass blocks almost all UVB but UVA still penetrates. If you sit directly next to a large window with sunlight falling on your face for extended periods, daily SPF is relevant. Monitor and phone screens do not produce meaningful UV.

How do I protect my eyes?

Sunglasses with proper UV400 protection — covering UVA and UVB — are essential in strong sun, particularly at altitude. Wraparound styles provide additional protection from rays entering at the sides. The fine skin of the eyelids also benefits from the shade of a wide-brimmed hat. Sunscreen should not be applied directly to the eyelid margin.

Does UV-protective clothing make sense?

Yes, particularly for water activities where sunscreen washes off. UPF 50+ rated clothing blocks the equivalent of SPF 50 across the fabric area. Choose breathable, quick-drying fabrics for comfort. UV clothing is a complement to sunscreen, not a replacement for exposed areas.

Does wearing sunscreen deplete vitamin D?

In practice, no. Most people do not apply enough sunscreen to block vitamin D synthesis entirely, and UVB exposure to small unprotected areas of skin is sufficient for most people’s vitamin D needs. If you are concerned about vitamin D levels, supplementation is a more reliable approach than relying on unprotected sun exposure.

Myth-busting

SPF 15 is as good as SPF 50

False. SPF 15 blocks 93.3% of UVB. SPF 50 blocks 98%. The UV dose reaching the skin is more than three times higher with SPF 15. The gap is meaningful for daily cumulative exposure.

UVA cannot be measured in sunscreen

False. UVA protection is measured by PPD testing, the PA rating system, the EU UVA circle logo, and the Boots Star Rating. The tools exist — the challenge is that not all markets require UVA measurement to be disclosed.

Organic and mineral sunscreens work completely differently

Oversimplified. Both primarily absorb UV radiation and dissipate it as heat. Mineral filters also scatter and reflect a smaller portion of light, which is what contributes to white cast. The old "mineral reflects, chemical absorbs" framing has persisted in marketing beyond what the science supports.

Organic sunscreens are dangerous hormonal disruptors

Oversimplified. EU Cosmetics Regulation requires extensive safety assessment before any filter is approved. Modern filters like Tinosorb S, Uvinul A Plus and Uvasorb HEB have over twenty years of safety data with excellent tolerability profiles. The concerns about some older filters — particularly oxybenzone, which is not approved in the EU — should not be extrapolated to the entire category of organic UV chemistry.

Sunscreens are destroying coral reefs

The picture is more nuanced than either side of this debate tends to acknowledge. Climate change, agricultural runoff and ocean acidification are the primary drivers of reef damage. However, research does confirm that zinc oxide nanoparticles — widely marketed as "reef-safe" — cause coral bleaching via photocatalytic reactive oxygen species. The reef-safe label has no standardised testing requirement. The most protective behaviour for reefs is physical coverage in the water.

Heat from organic sunscreens worsens melasma

Not supported. Both organic and mineral filters absorb UV and produce heat during the absorption process. The amounts produced are equivalent and not detectable at skin level. Strong UVA protection from a reliable formula is the most important factor for melasma management, regardless of filter type.

How to choose a high-quality sunscreen

A useful checklist when evaluating any sunscreen:

• SPF 50 or higher — for practical daily use accounting for under-application
• Verified UVA coverage — PA++++ or UVA circle logo, not just "broad spectrum"
• Photostable filters — check for photostability — some older filter combinations like ethylhexyl methoxycinnamate with butyl methoxydibenzoylmethane may be less photostable unless properly stabilised
• Fragrance-free — particularly important for sensitive, redness-prone and reactive skin
• Thoughtful filter selection — especially if environmental profile and sensitive skin are priorities. The UV filter safety article covers what to look for.
• Texture you will actually use — the most technically excellent sunscreen is worthless if you do not apply it consistently

Frequently Asked Questions

© NAYA Skincare. All information is for educational purposes and does not constitute medical advice.