Hand squeezing salt+blue non-nano mineral sunscreen from a blue tube into a palm on the beach

Is Non-Nano Zinc Oxide Safe? Here's What the Science Actually Says

I'm a light-skinned guy. I don't prefer a beach umbrella, I require it. I get sunburns walking through a large enough parking lot to go into the grocery store.

On vacation, people greet me with "you're starting to look a little red" or "you got a little sun today" before they say hello.

I also love being outside. Hiking, running, tennis, paddleboarding, walking on the beach, farming — all are things I thoroughly enjoy.

Because of my infatuation with the outdoors and my refusal to compromise quality of life for heliophobia, I've spent plenty of time reading the backs of sunscreen tubes.

As a child, mom did what she thought was best. Grab whatever's on the shelf, slather or spray it on, enjoy the fake coconut smell and trust that if a store sold it, it was safe. That was the 80's though, when Sears and Caldor were trusted, box store institutions.

As an adult, I started actually reading the ingredient lists — the same way I'd learned to read a cereal box or bag of chips back when I was untangling food marketing for a living — and found, with honestly little surprise, that sunscreen was part of the problem too. Another nicely designed tube full of chemical goo.

I couldn't help but think, first, what could all these chemicals do when put on the largest organ of our bodies, and secondly, what if we applied heat. It seemed like a chemist would be needed to break this down, and in fact, once I had done some preliminary research, I found that many already had.

There's a lot to unpack on the chemical side — but since salt+blue is a natural, broad spectrum sunscreen, let's start with the questions people actually ask about the natural stuff.

One question I get a lot, more than others is, usually some version of: is the zinc oxide safe? Does it get into me? What is non-nano zinc? Why is it any different?

So let's answer them. Not from a marketing perspective, but with what the research says — including the parts that complicate just a general "this is good, this is bad" synopsis.

What "non-nano" actually means

Zinc oxide is a mineral. When I was a kid, lifeguards would smear Zinka — a superthick, sometimes fluorescent-colored sunscreen made of zinc — on their noses to keep them protected. As a sunscreen, it works by sitting on top of your skin and dealing with UV rays before they reach you — reflecting some, scattering some, absorbing some. It doesn't get used up or chemically broken down by sunlight the way a lot of other filters do. (That's "photostability" and I'll cover that later.)

"Nano" versus "non-nano" comes down to one thing: particle size. A nanoparticle is smaller than 100 nanometers. For scale, a human hair is about 80,000 to 100,000 nanometers wide — so a nanoparticle is roughly a thousand times thinner than a hair, about the size of a virus. Non-nano particles are bigger than that 100-nanometer line, but still far too small to see. Both are invisible to us. The only thing that changes is whether the speck is small enough to slip through the microscopic gaps in your skin.

Why does the size of a speck of mineral too small to see matter? Because size is what decides whether that speck can physically get past your skin's outer barrier. If you follow where I'm going here — it's likely you've caught on that you don't want zinc to get past this barrier.

Does zinc oxide get into your bloodstream?

Short answer, no, the particles stay on the surface. The longer answer is more interesting.

Your stratum corneum is the outermost layer of your skin — a stack of dead cells whose entire job is to keep the outside world outside. I can't think of an appropriate metaphor here that isn't dangerously macabre, so I won't share one.

Non-nano zinc oxide particles are simply too large to cross it. They sit on top, in that dead layer and in the tiny furrows of your skin, and when you sweat, swim, or towel off, they come off.

Researchers have studied this. In a 2016 study, zinc oxide was applied to human skin under an airtight cover for 48 hours. These were conditions deliberately designed to force the particles inward. They still didn't reach the living layers underneath. An Australian government review of the whole body of evidence concluded that the likelihood of these particles penetrating past the surface into viable skin cells is extremely low.

So is nano zinc oxide dangerous?

Here I have to be straight with you, because the easy version of this story would be "nano gets into your body, non-nano doesn't," but that's not what the research says, and I won't pretend it does.

On healthy, intact skin, the evidence says both nano and non-nano zinc oxide mostly stay put. The same European and Australian reviews I keep coming back to looked at nano zinc and found it doesn't meaningfully get into living skin either. Europe's scientific committee cleared nano zinc oxide for sunscreen up to 25% — on healthy skin. They specifically flagged damaged or sunburned skin as an open question, which is exactly the thread I pull on below.

So why does nano exist at all? Looks. Grind the particles small enough and they stop scattering visible light — no white cast, the sunscreen goes on clear. That's the entire appeal.

So why did we still go non-nano? Because "mostly stays put on healthy skin" leaves a few doors open, and non-nano closes them:

  • Damaged skin. Cuts, eczema, sunburn, a fresh shave, post-procedure skin — the barrier that keeps particles out isn't fully intact. The data on nano there is thinner, and it's why a lot of dermatologists steer someone with compromised skin to non-nano.
  • Breathing it in. The one place regulators genuinely put their foot down on nano isn't your skin, it's your lungs. Europe specifically says keep nano minerals out of anything you spray or dust on, because inhaling particles that small is a different conversation than wearing them. (Definitely worth knowing next time you reach for a spray sunscreen.)
  • The reactive stuff. Under UV, uncoated mineral particles can kick off reactive molecules that could do damage if they got inside a cell. Good nano sunscreens coat their particles to stop this. Non-nano skips the whole issue by being too big to get into the cell to begin with.

None of this makes nano sunscreen a super villain. It just makes non-nano the version that I'm more comfortable using.

How that compares to chemical filters

This is where the question changes shape.

A pair of FDA-led studies published in JAMA in 2019 and 2020 looked at common chemical UV filters — avobenzone, oxybenzone, octocrylene, and others. They didn't just get absorbed in trace amounts. They showed up in the bloodstream at levels far above the threshold the FDA uses to decide a compound needs more safety study, and they were still detectable in blood and urine days after people stopped using them. Some were measured in breast milk.

I want to be fair about what that does and doesn't mean. The FDA has been explicit that "absorbed" is not the same as "unsafe" — detecting something in your blood is a reason to ask more questions, not a verdict. But notice that with chemical filters you're now asking an entirely different kind of question: what does this molecule do while it's circulating through me for days? With non-nano zinc oxide, that question mostly never comes up, because the stuff never goes for the ride. (I dig into the full mineral-versus-chemical comparison in a separate piece.)

There's one more difference worth naming, and it's the photostability I mentioned earlier: zinc doesn't break down in sunlight, so it keeps working as long as it's on you. A lot of chemical filters degrade as they absorb UV — avobenzone is notorious for it — which is part of why those sunscreens lean so hard on frequent reapplication.

What the regulators say

If you're the type who waits for the government to weigh in, here's the good news: the major bodies that have actually done the hard review keep landing in the same place.

In its 2021 proposed order on sunscreen, the FDA evaluated 16 UV filters and proposed exactly two as "generally recognized as safe and effective" or GRASE. Those two were zinc oxide and titanium dioxide. The other twelve weren't declared dangerous, but they were sent back for more safety data the agency said it still doesn't have. (Worth noting: that order is still proposed, not finalized — but it remains the agency's stated position.)

In Europe, the Scientific Committee on Consumer Safety reviewed zinc oxide and cleared it for use in sunscreen at concentrations up to 25%. Australia's regulator ran its own literature review and reached the same low-risk conclusion on skin penetration.

When the U.S., the EU, and Australia look at the same ingredient independently and walk away agreeing, that means something. That's about as close to consensus as this category gets.

So why doesn't everyone just use it?

Fair question. It's clear that it's the best ingredient for broad spectrum UV protection. It blocks both UVA (the aging rays) and UVB (the burning rays).

But the issue is that non-nano zinc oxide is harder to work with. It can leave a white cast. It takes a bit more deliberate rubbing-in than a sunscreen engineered to vanish instantly. It's easier to formulate something that feels like water if you reach for the chemical filters instead.

We went with non-nano anyway — and built the formula around skin-feeding plant oils so it actually earns its place on your body and face — because that tradeoff was the entire point. A few extra seconds of rubbing in exchange for more complete sun protection while not having to wonder what's circulating through you afterward strikes me as a deal worth making. I want to be in the sun and protected.

PRO TIP: After 2–3 minutes, work it in again and the white cast mostly disappears — the protection stays, it just stops looking like protection.

The bottom line

Armed with this information, the choice is pretty clear.

When you're using sunscreen, non-nano zinc is the way to go. It has better protection and you don't have to worry about any nastiness getting into your body while you're sipping mocktails on the Amalfi Coast or taking a beach break on your Costa Rican yoga retreat.

(It's also worth noting that all non-nano zinc products aren't always or necessarily super-clean. So be sure to read the labels and not be fooled by a non-nano product that contains other chemicals that you don't want on your skin.)

Frequently asked questions

Is non-nano zinc oxide safe for babies?

Yes. Non-nano zinc oxide is widely considered one of the gentlest UV filters available, which is why pediatric and sensitive-skin formulas so often rely on it. The particles sit on the skin's surface rather than absorbing, and zinc oxide has a long history of use on infant skin (it's the active ingredient in most diaper-rash creams). As with anything for a baby, check with your pediatrician — but mineral filters are generally the first choice clinicians point to.

Does zinc oxide absorb into the bloodstream?

The zinc oxide particles themselves stay on the surface of the skin and don't penetrate into living tissue. Sensitive isotope studies have detected a trace amount of dissolved zinc ion in blood and urine after several days of use — less than a hundredth of a percent of what's applied — which is negligible compared to the zinc you already get from food. The protective ingredient does its work on the surface and washes off.

What is the difference between nano and non-nano zinc oxide?

Particle size. Nanoparticles are smaller than 100 nanometers; non-nano particles are larger. The distinction matters because larger particles are physically too big to cross the skin's outer barrier, so there's no meaningful absorption question with non-nano. Nano research is mostly reassuring too, but non-nano removes the ambiguity entirely. The tradeoff is that non-nano can leave more of a visible white cast.

Is zinc oxide GRASE?

Yes — in its 2021 proposed sunscreen order, the FDA identified zinc oxide and titanium dioxide as the only two of 16 reviewed UV filters proposed as "generally recognized as safe and effective" (GRASE). That order has not yet been finalized, but it reflects the agency's current position, and it lines up with conclusions reached independently by regulators in the EU and Australia.

Kevin Gianni is the co-founder of salt+blue and Annmarie Skin Care and the author of Kale and Coffee. He's spent more than twenty years researching natural health and personal-care ingredients — reading studies, interviewing experts, and questioning dubious marketing. (He's also been using em-dashes well before AI made them suspicious, and has no intention of stopping.)

References

Back to blog

Leave a comment