If you've spent any time in the sun care aisle recently, you've probably noticed the words "mineral" and "chemical" being thrown around a lot. But what do they actually mean–and does the difference matter?
Short answer: yes. Here's what you need to know.
How Chemical Sunscreens Work
Chemical sunscreens use synthetic compounds–oxybenzone, avobenzone, octinoxate, homosalate, and others–to absorb ultraviolet radiation. When UV rays hit your skin, these chemicals absorb the energy and release it as heat.
The problem is that this process requires the chemicals to penetrate the skin to work. That's not a theory–the FDA itself published a study showing that several common chemical sunscreen ingredients enter the bloodstream after a single use, and can be detected for weeks afterward.
That doesn't automatically make them dangerous. But it does raise questions that the science hasn't fully answered yet.
How Mineral Sunscreens Work
Mineral sunscreens–sometimes called physical sunscreens–use zinc oxide or titanium dioxide as their active ingredient. Instead of absorbing UV rays, they sit on top of the skin and physically reflect them, like a mirror.
Because they don't need to penetrate the skin to work, they're generally considered a better option for sensitive skin, kids, and anyone who wants to minimize what gets absorbed into their body. The FDA has classified both zinc oxide and titanium dioxide as generally recognized as safe and effective.
What About the Reef?
This is where the difference becomes really significant. Oxybenzone and octinoxate–two of the most common chemical sunscreen ingredients–have been shown to cause coral bleaching, disrupt coral reproduction, and accumulate in marine ecosystems.
Hawaii banned both in 2021. The US Virgin Islands followed. More places are moving in the same direction.
Zinc oxide, by contrast, has not shown the same harmful effects. Non-nano zinc oxide–meaning particles large enough that they can't be ingested by marine organisms–is widely considered the reef-safe alternative.
Non-Nano: Why Particle Size Matters
You might see "nano" or "non-nano" on mineral sunscreen labels and wonder what it means. Nano-sized zinc oxide particles are extremely small–small enough to potentially be ingested by coral polyps and other marine life, and small enough to raise questions about skin absorption.
Non-nano zinc oxide uses larger particles that stay on the surface of the skin and are too big to be absorbed by coral. It's the more conservative, more ocean-friendly choice.
Seaker Sun Co uses exclusively non-nano zinc oxide.
The Trade-Offs
Mineral sunscreens aren't perfect. They can leave a white cast–the chalky residue you might associate with old-school zinc on a lifeguard's nose. Formulation has improved a lot, and a well-made mineral balm minimizes this, but it's worth knowing.
They also need to be applied generously and reapplied regularly, especially after swimming or sweating. Mineral protection doesn't chemically bond to the skin the way some chemical filters do.
But for anyone who cares about what goes into their body, what goes into the ocean, or both–mineral is the clearer choice.
The Bottom Line
Chemical sunscreens: absorbed into the skin, potentially problematic for coral reefs, plenty of open questions.
Mineral sunscreens: sit on top of the skin, physically reflect UV, reef-safe when non-nano, well-established safety profile.
If you want simple, clean sun protection that you can feel good about in the water, mineral is where to start.