Sun protection is talked about constantly, and most of us understand it matters — for our health, for our skin's long-term condition. Yet research continues to show that knowledge about SPF filters and how they actually work remains surprisingly thin. We reach for sunscreen in July but skip it in October. We layer two products with SPF and assume the numbers add up. We buy the highest number without knowing what it measures. Let's change that. Here's everything you need to know about UV radiation, sun protection factors, and choosing a sunscreen that genuinely works for you.
UV Radiation: What It Is and Why It Matters
Ultraviolet (UV) radiation is electromagnetic radiation emitted by sunlight. It's invisible to the naked eye, its intensity varies with time of day, season, altitude, and cloud cover — and it reaches your skin every single day, not just in summer. On the positive side, UV light stimulates vitamin D synthesis and supports mood. The problem is that regular, unprotected exposure accumulates damage across a lifetime, well beyond what the eye can see on any given day.
UV radiation is divided into three ranges based on wavelength: UVA, UVB, and UVC. UVC is almost entirely absorbed by the ozone layer and doesn't reach us in meaningful amounts. UVA and UVB, however, both reach the skin's surface — and both cause harm, though in very different ways.
UVA — The Ray That Ages
UVA accounts for approximately 95% of the UV radiation that reaches Earth's surface. It penetrates deep into the dermis — the skin's lower layers — where it generates free radicals, degrades collagen and elastin, reduces the skin's ability to retain moisture, and causes hyperpigmentation. The result is accelerated skin ageing: loss of elasticity, deepening wrinkles, and uneven skin tone. Critically, UVA-induced damage is largely irreversible.
UVA is present year-round, at a relatively consistent level regardless of season. It passes through clouds, glass windows, and even light clothing. This is why dermatologists recommend daily sunscreen use throughout the entire year — not only on beach holidays, but on ordinary commutes and working days.
UVB — The Ray That Burns
UVB makes up roughly 5% of UV radiation at ground level, but it is more energetically intense and more directly mutagenic than UVA. It penetrates to the basal layer of the epidermis, where it damages DNA, destroys proteins and cell membranes, and drives pigmentation — the familiar suntan, and sometimes sunburn. Long-term UVB exposure is closely associated with the development of skin cancers: melanoma, basal cell carcinoma, and squamous cell carcinoma.
UVB intensity peaks in summer, typically between 10 a.m. and 3 p.m. Unlike UVA, it is partially filtered by cloud cover and fog, but it does penetrate water and glass. The combination of high UVB in summer and background UVA throughout the year is precisely why broad-spectrum protection — covering both ranges — is the only genuinely adequate approach.
SPF Explained: What the Number Actually Tells You
SPF stands for Sun Protection Factor. It is an internationally standardised measure of a product's ability to protect against UVB radiation specifically. The number reflects what fraction of UVB rays are blocked:
- SPF 15 — blocks approximately 93% of UVB
- SPF 30 — blocks approximately 97%
- SPF 50 — blocks approximately 98%
- SPF 50+ — blocks approximately 98.5%
No sunscreen provides 100% protection, and the difference between SPF 50 and SPF 50+ is marginal in absolute terms. What matters far more is consistent, correct application — a point we'll return to shortly.
What About UVA Protection? PA, PPD, and IPD
Because SPF only measures UVB protection, additional systems exist to describe UVA coverage. The PA system was developed in Japan and is widely used on Korean and Asian cosmetics. It uses a "+" scale:
- PA+ — some UVA protection
- PA++ — moderate UVA protection
- PA+++ — high UVA protection
- PA++++ — very high UVA protection
You may also encounter PPD (Persistent Pigmentation Darkening) or IPD (Immediate Pigmentation Darkening) ratings. Both measure UVA protection via different pigmentation responses. The European Commission recommends that any UVA rating on a product should correspond to at least one-third of the SPF value — so an SPF 50 product should have a meaningful UVA protection level to match. When shopping for complete coverage, look for products that explicitly state broad-spectrum or UVA/UVB protection, and check for PA++++ if you're choosing from K-beauty ranges.
[tip:K-beauty sunscreens are widely considered among the most advanced on the market — typically lightweight, high PA-rated, and formulated to sit comfortably under makeup. Many European shoppers have discovered them as a daily-use alternative to thicker Western formulations.]What's Inside a Sunscreen?
Understanding the two main types of UV filters helps you choose a product that matches both your skin's needs and your personal preferences.
Chemical (organic) filters are compounds that absorb UV radiation and convert it into harmless heat energy. They include derivatives of p-aminobenzoic acid, p-methoxycinnamate, salicylic acid, and camphor. Some offer narrow-spectrum protection (UVB only), while others — particularly newer broad-spectrum agents — cover both UVA and UVB. Chemical filters tend to feel lighter on the skin and leave no white cast, making them popular in everyday cosmetics.
Physical (mineral) filters — principally Titanium Dioxide and Zinc Oxide — work differently: they reflect and scatter UV radiation rather than absorbing it. Physical filters provide reliable UVB protection and good UVA coverage, and they are generally well tolerated by sensitive, reactive, and atopic skin. They were historically associated with a white residue, though modern micronised formulations have largely addressed this. Physical-filter sunscreens are also the recommended choice for infants and young children.
Beyond the filters themselves, many sunscreens incorporate antioxidants — vitamins C and E, coenzyme Q10, beta-carotene, and flavonoids — to help neutralise the free radicals generated by UV exposure. These are genuinely useful additions, not just marketing. Natural oils such as shea butter, argan, macadamia, and avocado may also appear in formulations; while they contribute to skin feel and hydration, their intrinsic UV protection is minimal and should not be counted as a substitute for proper filters.
Choosing the Right Sunscreen for Your Skin Type
The best sunscreen is the one you'll actually use every day — and that means finding a formula your skin tolerates well and that fits your routine. A few general guidelines help narrow it down:
- Oily or combination skin — opt for lightweight gel or fluid textures that won't clog pores or feel heavy. Many K-beauty gel sunscreens were specifically designed with this concern in mind.
- Dry or mature skin — look for hydrating formulations with added moisturising ingredients like hyaluronic acid or ceramides. Sun creams with a richer texture offer both protection and nourishment.
- Sensitive, atopic, or reactive skin — physical (mineral) filters are typically better tolerated. Fragrance-free, minimalist formulations reduce the risk of irritation.
- Acne-prone skin — non-comedogenic, mattifying formulations help prevent breakouts while maintaining protection.
For daily face use, SPF 30 is considered an acceptable minimum in typical European conditions, though SPF 50 or 50+ is always the better choice — particularly for lighter skin tones. On the body during direct sun exposure, the same principles apply. Explore our sun creams and lotions collection to find the right format for your needs.
[products:beauty-of-joseon-relief-sun-rice-probiotics-spf-50-50-ml, isntree-hyaluronic-acid-watery-sun-gel-spf-50-pa-uva-uvb-50-ml, cosrx-aloe-soothing-sun-cream-spf-50-50-ml, nacomi-next-level-face-cream-spf-50-uv-city-50-ml, mary-may-cica-soothing-sun-cream-spf50-50-ml]Common Mistakes That Undermine Your Protection
Applying sunscreen is only effective if applied correctly. Research shows that most people apply roughly 0.5 mg per cm² of skin, while SPF ratings are tested at 2 mg per cm². Using half the recommended amount means you're getting somewhere between 50–60% of the protection stated on the packaging. In practical terms: use more than you think you need, and reapply every two hours during outdoor exposure or after swimming, even with water-resistant formulations.
A few other points worth noting. SPF values do not add together — applying SPF 30 over SPF 20 does not yield SPF 50. The higher rating in the stack is your effective protection level. And sunscreen should be the last skincare step before makeup — applied after serums and moisturisers, before foundation or powder. For the face, this order is not optional: it ensures the film of protective filters sits correctly on the skin surface.
[warning:Facial sunscreens can be applied to the body if needed, but body sunscreens should never be used on the face. Body formulations are not designed for facial skin and may cause clogged pores, irritation, or breakouts.]For those who prefer on-the-go or reapplication-friendly formats, sun sticks offer a convenient alternative to creams and gels — easy to carry, precise to apply, and typically suitable for use over makeup. Our facial cosmetics range includes several options for different skin concerns and daily scenarios.
[products:pyunkang-yul-ato-mild-sun-cream-spf50-pa-75-ml, derma-sun-face-lotion-spf-30-50-ml, abib-quick-sunstick-protection-bar-spf50-22-g, isntree-hyaluronic-acid-airy-sun-stick-spf50-22-g]Sun protection is not a seasonal habit. UV radiation is present every day, through cloud cover and glass, in every month of the year. It's also one of the most evidence-backed interventions in skin health — with consistent use, quality skincare that includes daily SPF application genuinely makes a difference to how skin ages, and to long-term health outcomes. The product choices available today — including the particularly well-formulated Korean sun protection lines — make it easier than ever to find something that suits your skin and that you'll reach for every morning.
[note:All products at Medpak are shipped from within the EU — no customs delays or extra fees for customers across Europe.]
