Educational guide · 14 min read
Sunscreen is the most-evidenced anti-aging product in skincare — but most users apply the wrong amount, choose the wrong SPF, and don't understand the difference between UVB and UVA. This is the guide that explains what the labels really mean, how to apply enough to get the protection you paid for, and how to pick the right filter chemistry for your skin.
Last updated: August 23, 2026 · Sources: TGA Australia, EU COLIPA 1/3 ratio, Diffey 2001, Marrot 2020 Mexoryl 400
Sunscreen protects skin from ultraviolet (UV) radiation, which is divided into three bands by wavelength: UVC (100–280nm, blocked by the atmosphere), UVB (280–315nm, the "burning ray"), and UVA (315–400nm, the "aging ray"). A modern broad-spectrum sunscreen absorbs or reflects both UVB and UVA, preventing sunburn (UVB), photoaging (UVA), hyperpigmentation (UVA + visible light), and reducing long-term skin cancer risk.
The challenge: sunscreen is one of the most misunderstood skincare products. Marketing leads with SPF, but SPF only measures UVB protection — the most-cosmetic, most-misleading number on the bottle. A sunscreen labeled "SPF 50" can be a UVA-blocker (PPD 30+, balanced protection) or a UVA-barely-touched formula (PPD 8, basically UVB-only despite the SPF number). The Australian and EU standards require UVA-PF ≥ 1/3 of labelled SPF for "broad spectrum" — anything below that ratio is, in regulatory terms, a UVB sunscreen with extra marketing.
The bottom line: SPF is the price of entry, not the metric that matters. For real anti-aging and pigmentation prevention, the UVA-PF (PPD) is the number to look at. PPD ≥ 30 = strong UVA protection (Mexoryl 400 territory). Anything below PPD 15 at SPF 50+ is a marketing-grade "broad spectrum" claim.
UV radiation is split into two bands that penetrate the atmosphere and reach your skin, and they do different things:
Penetrates to the epidermis (the outermost skin layer). Causes sunburn, immediate tanning, and is the primary driver of non-melanoma skin cancers (BCC, SCC). Peaks 10am–4pm, varies by season and latitude. SPF measures UVB protection specifically. Window glass blocks most UVB.
Blocked by: all sunscreens (chemical + mineral). Window glass: blocks most UVB.
Penetrates deeper, into the dermis where collagen and elastin live. Causes photoaging (wrinkles, sagging), melasma, post-inflammatory hyperpigmentation, and contributes to melanoma risk. UVA is further divided into UVA2 (315–340nm) and UVA1 (340–400nm). UVA1 is the deepest-penetrating — reaches the dermis and breaks down collagen directly. UVA is consistent year-round and penetrates clouds + window glass.
Blocked by: broad-spectrum sunscreens (UVA-PF / PPD ≥ 1/3 of SPF). Window glass: does NOT block UVA — most office-window UV exposure is UVA.
This is why the SPF 50 / PPD 46 of La Roche-Posay UVMune 400 is a fundamentally different product from an SPF 50 / PPD 10 formulation. Both prevent sunburn equally; only the UVMune 400 covers the deep UVA1 that breaks down collagen.
SPF (Sun Protection Factor) is a lab-measured ratio: how much UVB radiation is needed to cause sunburn on protected skin vs unprotected skin. SPF 30 means you can stay in the sun 30× longer before burning — assuming you apply the full 2 mg/cm² that the test uses. In real-world use, most people apply 0.5–1.0 mg/cm², getting roughly half the labelled protection.
The percentage of UVB blocked is logarithmic, not linear. SPF 15 blocks ~93%, SPF 30 blocks ~97%, SPF 50 blocks ~98%, SPF 100 blocks ~99%. The jump from SPF 30 to SPF 50 is meaningful (more headroom for under-application); the jump from SPF 50 to SPF 100 is mostly cosmetic — both deliver roughly the same real-world protection.
SPF 30 — minimum for daily indoor wear
Adequate for office workers, indoor days, brief outdoor exposure. Filters ~97% of UVB. The minimum in most regulatory standards.
SPF 50+ — the AU standard daily minimum
TGA Australia and most dermatology guidelines recommend SPF 50+ as the daily minimum, regardless of skin type. Filters ~98% of UVB. Provides meaningful headroom for under-application.
SPF 70–100 — extreme UV days only
Tropical, alpine, outdoor labour. Diminishing returns above SPF 50 for most users. The higher filter load often increases irritation and cosmetic issues (white cast, greasiness).
All 4 filter categories are sold as "sunscreen" on the label. They differ in chemistry, protection profile, skin feel, and reef impact. The right pick depends on your skin type, daily UV exposure, and any reef commitments.
Modern chemical filters — Mexoryl SX/XL/400 (L'Oréal), Tinosorb S/M (BASF), Uvinul A Plus/T 150 (BASF) — are highly photostable and achieve the highest UVA-PF values (Mexoryl 400 reaches PPD 46). Absorb UV and convert to heat. Most have minimal skin irritation in modern formulations.
Pros: highest UVA-PF options (Mexoryl 400), lightweight feel, invisible finish. Cons: not reef-safe (oxybenzone/octinoxate banned in some regions), need 15–20 min to bind before sun exposure.
Try: La Roche-Posay Anthelios UVMune 400 · Bioderma Photoderm MAX · The Ordinary UV Filters SPF 45
Zinc oxide and titanium dioxide. Sit on the skin surface and reflect/scatter UV. Inherently reef-safe (Hawaii/Mexico/Palau compliant). Work immediately on application — no 20-minute wait. No systemic absorption. The trade-off: harder to spread, can leave white cast on darker skin tones, lower peak protection per gram than modern chemical filters.
Pros: reef-safe, immediate protection, no systemic absorption, suitable for sensitive skin / pregnancy / children. Cons: white cast (solved by "sheer" formulas or tinted), thicker feel, lower UVA-PF.
Try: CeraVe Hydrating Mineral SPF 30 · Neutrogena Sheer Zinc SPF 50+ · Drunk Elephant Umbra SPF 30
Combines organic filters for high UVA/UVB absorption with mineral filters (typically titanium dioxide) for the visible-light range. Often the best balance for sensitive skin — high protection with reduced chemical filter load. The mineral component adds visible-light protection that chemical filters alone don't provide (relevant for hyperpigmentation in skin of colour).
Try: La Roche-Posay Anthelios XL Comfort Cream · RoC Mineral SPF 50 (tinted mineral-hybrid)
Zinc oxide + iron oxide pigments. The iron oxide tint eliminates the white cast that makes most mineral sunscreens hard to wear on medium/dark skin tones, and adds visible-light protection (blue light from screens contributes to pigmentation in skin of colour). Excellent for medium-to-deep skin tones and anyone who has had trouble with mineral sunscreens looking chalky.
Try: RoC Mineral SPF 50 Tinted · La Roche-Posay Anthelios tinted mineral
Studies consistently show that people apply 25–50% of the amount needed to achieve the labelled SPF. The lab test uses 2 mg/cm² — about 1/4 teaspoon (1.25 ml) for face + neck alone. The "two-finger rule" (a line of sunscreen along the length of your index and middle finger, from base to tip) is a quick visual guide for face-only application. A full-body application for an average adult is about 35 ml (a shot glass).
Face + neck: 1/4 teaspoon (1.25 ml)
The minimum to achieve the labelled SPF. Two-finger method for face alone; add another half-finger for neck and ears.
Full body: 35 ml (a shot glass)
For beach or full-exposure days. Most people use 1/4 of this. Reapply after swimming, sweating, or towel-drying.
Reapply every 2 hours
Diffey 2001 — the SPF rating declines steadily after application regardless of activity. Two hours is the maximum interval. Water-resistant products last 40 or 80 minutes of water exposure, not all day.
Sunscreen is the only skincare product that should be used 365 days a year. UVA is consistent year-round, penetrates clouds, and reaches skin through window glass. Here's the routine that delivers real protection:
Apply 1/4 teaspoon (1.25 ml) of SPF 50+ broad-spectrum sunscreen as the last step of your morning skincare routine, after moisturiser. Wait 15–20 minutes before sun exposure (chemical filters) or apply immediately (mineral). Reapply if sun exposure exceeds 2 hours.
Apply full 35 ml (a shot glass) 20 minutes before going outside. Reapply every 2 hours, or immediately after swimming / heavy sweating / towel-drying. Use SPF 50+ with water resistance ≥ 40 min. Add a hat, sunglasses, and UPF clothing for extended exposure.
Lin 2005 — applying L-ascorbic acid 15% + vitamin E + ferulic acid underneath SPF 50 doubles photoprotection vs either alone. The antioxidants neutralise the free radicals that slip past the filters. Use a CE Ferulic serum (SkinCeuticals, Paula's Choice C15) or topical vitamin C in the morning before SPF.
Mineral-only (CeraVe Hydrating Mineral, Neutrogena Sheer Zinc). Avoid chemical filters if you have a history of photoallergic reactions. Look for "fragrance-free" + "essential-oil-free" formulations.
Bioderma Photoderm MAX Aquafluide or The Ordinary UV Filters SPF 45. Lightweight, oil-free, won't clog pores. Avoid thick mineral lotions that can trigger breakouts.
La Roche-Posay Anthelios XL Comfort Cream — the hybrid formula with titanium dioxide adds emollient feel. Or layer SPF over a richer moisturiser. Drunk Elephant Umbra SPF 30 if you can afford premium tier.
Tinted mineral (RoC SPF 50 tinted, La Roche-Posay tinted) eliminates the white cast that makes most mineral sunscreens hard to wear on medium-to-deep skin tones. Visible-light protection from iron oxide pigments also helps prevent hyperpigmentation.
Mineral-only is the conservative default — TGA Australia lists zinc oxide and titanium dioxide as Category A. CeraVe Hydrating Mineral or Neutrogena Sheer Zinc. Avoid chemical filters if you have any concern about systemic absorption, though the FDA currently considers modern chemical filters safe in pregnancy.
Mineral-only — zinc oxide + titanium dioxide are inherently reef-safe. Avoid oxybenzone and octinoxate (banned in Hawaii, Mexico, Palau). The Neutrogena Sheer Zinc 21.6% and CeraVe Hydrating Mineral are both mineral-only and reef-compliant.
The concern: oxybenzone and octinoxate (two common chemical UV filters) have been shown in laboratory studies to damage coral larvae at concentrations as low as 62 parts per trillion. Hawaii banned both in 2018, followed by Mexico (2021), Palau (2020), Bonaire, Aruba, and the US Virgin Islands.
The nuance: the coral-larvae studies used concentrations far higher than what washes off a swimmer. The actual environmental impact at realistic swimmer-loading rates is still debated — but the precautionary principle has won, and most major sunscreen brands have removed oxybenzone/octinoxate from their "reef-safe" lines. Modern chemical filters (Tinosorb S/M, Mexoryl, Uvinul) are not on any banned list.
The bottom line: if you swim near coral — in Thailand (Koh Lipe, Phi Phi), Australia (Great Barrier Reef), the Caribbean, Hawaii — use mineral-only sunscreen. If you swim in pools or open ocean without coral, the choice is yours.
Mineral-only doesn't always mean reef-safe. Some "mineral" sunscreens contain nano-sized zinc oxide particles that may also have environmental impacts. Look for "non-nano zinc oxide" on the label for the most eco-conscious pick.
Marginally — SPF 30 blocks ~97% of UVB, SPF 50 blocks ~98%. The jump is small in lab conditions, but meaningful in real-world use because most people apply 25–50% of the test amount. SPF 50 gives more headroom for under-application. For daily indoor wear, SPF 30 is acceptable. For outdoor days, SPF 50+ is the AU/TGA standard.
Yes, if you're near windows. UVA penetrates glass — most office-window UV exposure is UVA, which contributes to photoaging and pigmentation. If your desk is not next to a window, the risk is minimal. If you have a home office with sun streaming in, daily SPF is worthwhile.
Both are considered safe by TGA Australia, FDA US, and EU SCCS. Mineral (zinc oxide, titanium dioxide) has zero systemic absorption — it sits on the skin surface and reflects UV. Modern chemical filters (Tinosorb, Mexoryl, Uvinul) absorb small amounts systemically but have decades of safety testing. The practical differences: mineral is reef-safe and pregnancy-default; chemical can achieve higher UVA-PF.
Yes, but the level varies. AU TGA and EU COLIPA require UVA-PF ≥ 1/3 of labelled SPF for "broad spectrum". A "broad spectrum SPF 30" must have UVA-PF ≥ 10; "broad spectrum SPF 50+" must have UVA-PF ≥ 17. The UVMune 400 PPD 46 is far above the minimum — that's the gold standard. Avoid sunscreens that don't specify UVA-PF / PPD on the label or packaging.
Three common causes: (1) applying too much — the excess rolls off when makeup touches it; (2) layering too soon — give SPF 60 seconds to absorb before foundation; (3) formula mismatch — thicker mineral creams pill more than serum or fluid textures. The fix: switch to The Ordinary UV Filters SPF 45 Serum or La Roche-Posay UVMune 400 Invisible Fluid, wait 60 seconds between layers, and use less SPF (still at 1/4 teaspoon).
No. Both chemical and mineral filters degrade over time. Most sunscreens have a 2–3 year shelf life unopened; once opened, use within 12 months. Heat accelerates degradation — don't stockpile sunscreen in hot bathrooms or cars. If your sunscreen has changed consistency (separated, grainy, watery) or smell, discard regardless of the printed expiry date.
These 10 brands are featured on every vitfacts.com comparison page. We track them for ingredient transparency, third-party testing, and Thailand availability.
Since 2013
A clinical-active cult brand built around single-molecule formulas at price points that disrupted the skincare industry. Sold at Sephora, Chemist Warehouse, and most Thai beauty retailers.
Since 2005
A dermatologist-developed US brand built around ceramides + MVE controlled-release technology. Sold at Chemist Warehouse, Watsons, Boots, and most major pharmacies worldwide.
Since 1952
A 70-year-old P&G mass-market skincare brand with clinical retinol offerings in the Regenerist line. Widely stocked at supermarkets, Watsons, Boots, and Chemist Warehouse.
Since 1930
A dermatologist-recommended US brand with a deep retinol catalog (Rapid Wrinkle Repair, Stubborn Texture). One of the most-searched retinol brands on both AU and TH retail sites.
Since 1975
A French pharmacy-grade dermocosmetics brand endorsed by dermatologists worldwide. Their Retinol B3 serum and Redermic lines are bestsellers in both Australian and Thai pharmacies.
Since 1995
A research-driven US skincare brand founded by chemist Paula Begoun. The Clinical 1% Retinol Treatment is one of the most-cited retinol products in dermatology literature. Sold via own site, iHerb, and Sephora.
Since 1957
A US skincare brand that has specialised in retinol since 1995 — one of the first mass-market retinol lines. The Retinol Correxion line is a household name in AU and TH pharmacies.
Since 1977
A French dermo-cosmetic brand under the NAOS group, widely sold at Watsons, Boots, and Thai independent pharmacies. Recently expanded retinol line with the Retinol+C10 serum.
Since 2012
A US premium "biocompatible" skincare brand owned by Shiseido. The A-Passioni 1% Retinol Cream is widely considered the gold standard in the premium retinol segment. Sold at Sephora, Mecca, and iHerb.
Since Thailand (founded year unverified — about/story page does not state a year)
A Thai clinical-skincare brand (อิงกุ) built around ingredient transparency and research-led formulations. Operates two product lines: topical skincare (Green Tea Biome Balance cleansers/creams, Green Tea Retinol Serum Shot, Vitamin C AOX Glowing Serum, broad-spectrum sunscreens) and an oral INU range (astadaily / astanext Astaxanthin + Vitamin E antioxidant supplements).
Why these 10? See the VitFacts editorial policy page (forthcoming) for the criteria — minimum 10 years of documented safety record, public certificate-of-analysis policy, and verifiable Thailand distribution.
Not medical advice. This article is for educational purposes only and does not constitute medical advice. Consult a board-certified dermatologist before changing your sun-protection routine, especially if you have a history of skin cancer, photosensitivity, or are taking photosensitising medication.