UV Filters Explained: What's in Your Sunscreen, Graded

Read this first: this guide grades UV-filter ingredients on the published evidence – photostability, spectrum, formulation behaviour. It is not sun-safety advice, not a recommendation to rely on any ingredient for sun protection, and not medical guidance. Sunscreen is a regulated OTC drug in many countries; use a finished, approved SPF product as directed, and treat sun protection as a medical matter. With that firewall stated plainly, here's what actually differs between the filters.

Sunscreen is the one skincare category that is a drug, not a cosmetic, almost everywhere – which is exactly why the ingredients inside it deserve a neutral reference. The finished product's SPF is a regulated claim we don't touch. But the filters themselves differ enormously in quality, and most people have no idea their sunscreen may be built on a filter that half-degrades in the first hour of sun.

Two families, one job

Every UV filter does the same thing – absorb or scatter ultraviolet radiation before it reaches skin – by one of two mechanisms.

Inorganic (mineral) filters – zinc oxide, titanium dioxide – sit on the surface and mainly scatter and absorb UV. They are broadly photostable (they don't break down in light), gentle, and rarely sensitising, which is why they dominate sensitive-skin and children's products. The historical trade-off was cosmetic: a white cast, improved but not eliminated by modern micronised grades.

Organic (chemical) filters – a large family – absorb UV and convert it to trace heat. They are cosmetically elegant (no white cast) and can be tuned for specific parts of the UV spectrum. The catch is that some are photounstable – they degrade under the very sunlight they're meant to defend against – and approval varies wildly by country. This is where the real quality gap lives.

The quality gap: photostability and spectrum

Here is the detail the marketing rarely surfaces, and the reason two "broad-spectrum" sunscreens can be worlds apart. A filter is only as good as its ability to survive sun exposure and cover the whole UV range (UVB and both UVA-I and UVA-II).

• The modern broad-spectrum, photostable organic filters – bemotrizinol, DHHB, ethylhexyl triazone, bis-octrizole (Tinosorb M) – are excellent: wide coverage, stable in light, well-tolerated. Several are approved in the EU, Asia and Australia but not by the US FDA, whose approved-filter list hasn't meaningfully expanded in decades. This is why sunscreens in Europe and Korea are often technically ahead of US ones.
• Avobenzone is the workhorse UVA filter in much of the world – but it is notoriously photounstable on its own, degrading significantly within an hour of sun unless stabilised by other filters (octocrylene, or the newer filters above). A well-built formula stabilises it; a careless one doesn't.
• The older, more controversial organics – oxybenzone, octinoxate – carry both photostability limits and environmental/regulatory scrutiny (some reef jurisdictions restrict them). Present in many legacy products, increasingly formulated out.

The evidence tiers (of the filters as ingredients)

Graded on filter quality – photostability, spectrum, tolerability – not on any product's SPF:

• Grade A – the modern broad-spectrum workhorses: zinc oxide (mineral, photostable, gentle), bemotrizinol, DHHB, ethylhexyl triazone, bis-octrizole. The filters you'd want doing the work.
• Grade B – solid with a caveat: titanium dioxide (great UVB, weaker on long UVA; often paired), avobenzone (essential UVA coverage but must be stabilised).
• Grade C – legacy / limited: octinoxate, octocrylene, oxybenzone – older filters with photostability, spectrum, or regulatory limitations, being designed out of better formulas.

Why your country's sunscreen is different

A genuinely useful thing to understand: the filter approved-lists differ by regulator, so "the best sunscreen" is partly a jurisdiction question. The EU, Australia, Japan and Korea permit the modern photostable filters above; the US does not, and leans harder on avobenzone-plus-stabiliser systems. Neither is unsafe – approved sunscreens work – but it explains why an EU or Korean sunscreen can feel and perform better than a US one built on an older filter set. This is about the ingredients, not a claim about any product's protection.

The one thing to take away

For the filters, one question separates good from mediocre:

Is it broad-spectrum AND photostable – and approved where you are?

A filter that covers the whole UV range and survives sunlight (the grade-A set, or avobenzone properly stabilised) is doing the real job. A "broad-spectrum" label built on an unstabilised or photounstable filter is a weaker proposition than it sounds – though this is about ingredient quality, and never a substitute for using an approved SPF product as directed.

In the register

The modern workhorses: zinc oxide, bemotrizinol, DHHB, ethylhexyl triazone, bis-octrizole (Tinosorb M). Solid-with-caveat: titanium dioxide, avobenzone. Legacy filters: octinoxate, octocrylene, oxybenzone. And the practical companion: how to use sunscreen.

How we grade: methodology.

Neutral evidence-based reference from Vallydia. This grades UV-filter ingredients on the published evidence (photostability, spectrum, tolerability); it is NOT sun-safety advice, NOT a protection claim, and NOT medical guidance. Sunscreen is a regulated over-the-counter drug in many jurisdictions – choose and use a finished, approved SPF product as directed, and treat sun protection and any skin-cancer concern as a matter for qualified professionals. We grade ingredients as commonly formulated, not any single brand; Vallydia does not sell sunscreen and grades these as independent reference.