Skincare Education Series
Through our education series, we will help explain the science that goes into formulation our skincare and suncare products to help you better understand why we developed them, what are the benefits, and which type of product is best for your skin.
Zinc Oxide Guidebook:
What is it?
Why Does It Work?
Who Is It Best For?
& More Questions Answered
You Asked, We Answered
Sunscreen is the #1 investment you can make in the health of your skin. Shopping for a sunscreen on-line is hard because it can be confusing and difficult to determine what is true with so much information on the internet. We have put together this guide to zinc oxide to help dispel some popular myths, better explain what zinc does, and help educate you with honest scientifically-supported information on this key mineral active ingredient.
What is zinc oxide?
Zinc oxide (ZnO) is an inorganic mineral found in the Earth, that has a unique property of adequately absorbing UV light through both the UVA and UVB wavelengths. This is why it is used as an effective active UV filter for sunscreens. Zinc oxide remains as a predetermined particle size in a sunscreen because of low solubility and is considered an inorganic compound (meaning it contains no carbon atoms).
What does zinc oxide do?
It is used as a insoluble inorganic UV filter in mineral sunscreens to protect the skin against harmful ultraviolet light wavelengths from the sun. Zinc oxide reflects or back scatters 5% of the UV light passing through the sunscreen and also act as semi-conductor to absorb photons with electron shifts to a different valence band, so a harmful wavelength is converted to a less harmful or innocuous wavelength.
What is the best filter for optimum protection in North America?
Zinc Oxide remains the best filter for true broad spectrum protection in North America, especially when it comes to protecting against UVA light. It has the most robust safety and efficacy data and alongside Titanium Dioxide, one of two filters that currently meet the FDA’s most stringent safety rating of GRASE (Generally Recognized as Safe and Effective). A short but good rule of thumb to remember- the more Zinc Oxide a sunscreen has, the better broad-spectrum protection it will provide. We recommend a concentrations as close to 25% zinc oxide as possible. The more Zinc, the better.
Titanium dioxide can give mostly UVB or can extend its protection to shortwave UVA, depending on the particle size. As the particle size gets smaller, the protection (attenuation) curve of titanium dioxide shifts more into the UVB range and gives less short wave UVA and little to no long wave UVA into the visible light spectrum. It can also give protection in the infrared portion of light. Titanium dioxide does not adequately give long wave UVA in comparison to zinc oxide. This is crucial to note- as no sunscreen that contains only titanium dioxide can provide sufficient long wave UVA protection.
Zinc oxide, on the other hand, extends its protection from the UVB, through to the short wave UVA, long wave UVA into the visible light spectrum. When used in sufficient concentration (as close to 25% concentration), it truly gives broad spectrum protection in a way that titanium dioxide simply cannot.
When it comes to sun protection, mineral sunscreens with high concentrations of zinc oxide remain the gold standard for broad-spectrum coverage, visible light protection, and skin tolerance.
Don’t fall for internet myths—look past SPF numbers, white-cast rumors, or marketing jargon. A well-formulated mineral sunscreen is not just safe and effective; it’s one of the most powerful tools you have to protect your skin from UV damage and premature aging.
By choosing a zinc oxide mineral sunscreen, you’re protecting your skin from sunburn, premature aging, and long-term UV damage—safely and reliably.
At The Sunscreen Company, we prefer zinc oxide as our main choice of UV filter as it provides better long wave protection and even visible light attenuation. When used at a sufficient concentration as close to the maximum of 25%, it gives excellent broad-spectrum protection.
Non-nano sized Zinc Oxide Explained
We very often wrestle with how to answer this very complicated question with a simple answer. Simply put, we use a supply of Zinc Oxide that is Ecocert Certified Organic. Ecocert does not currently certify products that are considered nano as organic. Therefore, in simple terms, our zinc oxide can be considered non-nano. However, we caution consumers to delve deeper into these types of claims. There is no current global standard or test for determining what is considered nano sized. This means that suppliers can use their own in-house tests to determine whether their zinc oxide particles are below 100 nm. in size. Results can differ dramatically depending on what type of test is used. Furthermore, while a lab might detect the presence of nano-particles, these particles might not exist as such in real life conditions in finished formulas. Zinc Oxide especially tends to aggregate into larger clumps that formulators need to find ways to prevent in order to create uniform dispersions. Nano-particles have also been shown up until 30 nm in size to have robust safety when used in lotion based sunscreens. The EU currently only recommends avoiding nano particles in spray or powder form. Finally, many brands may rely on their suppliers information about whether their zinc oxide or titanium dioxide contains nano-particles and lack the ability to delve critically into their testing and reliability of their data. We would rather consumers look for options that contain high enough concentrations of zinc oxide rather than focus on particle size of their mineral filters.
Can Zinc Oxide Be Transparent?
You’ve probably seen influencers posting videos of zinc oxide as a stark white powder, claiming that mineral sunscreens can never be transparent. But just because zinc oxide starts as a white powder doesn’t mean it has to stay that way on skin.
Modern sunscreen formulation has come a long way. Instead of simply mixing in raw zinc oxide powders (a method that often leads to thick, chalky formulas), today’s cosmetic chemists use zinc oxide dispersions—liquid suspensions designed to stabilize and evenly distribute particles. These dispersions can even be matched with carrier fluids that bend light in a way that makes the particles look invisible on skin.
The result? Mineral sunscreens that are elegant, lightweight, and transparent—no white cast required.
Today’s formulations are transparent, safe, and effective for all skin types.
Transparency is Relative
Let's first begin by clarifying the terms. The perception of transparency depends on skin type since what might work really well for someone with pale Skin Type I but will not work for someone with darker skin that is Type VI. You'll often see this with a lot of Skinfluencers that are demoing a mineral SPF; they will add the caveat that what works for them, might not work for all. To be clear, we do have formulas that are 100% transparent as in they will rub into the skin with some agitation to be completely invisible for all skin types. Our current best-selling mineral sunscreen, Ava Isa Sun-e-Serum Drops SPF 35 will apply after minimal blending to be clear or invisible on all skin types.
Are there other mineral filters that are more transparent than zinc oxide?
If you are looking for a very transparent mineral option, it’s always great to start with the ingredient list in either the actives or inactives. If it contains titanium dioxide then you can think of it as having a stronger white background to the formula. Titanium dioxide can also give a grey ashen aspect to the skin as well so something to consider. If you are a darker skin tone, then we highly recommend looking for a zinc oxide-only, mineral option. You are not 100% guaranteed that all options out there on the market will be transparent but you will have a better chance.
Transparency also relates to a scientific phenomenon called Index Matching where you match the Refractive Index of the particle in the carrier you are dispersing it into. Titanium Dioxide has a higher refractive index and is harder to match. We’ve found a supplier of zinc oxide that expertly matches the refractive index of the carrier (medium chain triglycerides) and this helps to make our sunscreens as transparent as they are.
To be frank, titanium dioxide will always be less transparent than a possible dispersion of zinc oxide. This partially relates to particle size. Titanium dioxide has gotten more transparent as suppliers have made the particles smaller. The downside of a smaller particle size is that it shifts protection from short wave UVA to be predominantly UVB. For this reason, you should never use a mineral sunscreen that exclusively uses titanium dioxide as its active UV filter. It will not have any protection in the long wave UVA and would not be considered truly broad spectrum. Zinc oxide provides better broad spectrum protection
Again, our Ava Isa Sun-è-Serum Drops SPF 35 and Ava Isa Every Morning Sunscreens are absolutely transparent, any skin tone can use them. Our new Ava Isa Every Morning SPF 30 dries transparent after rubbing it in, and only requires slightly more blending than our Sun-è-Serum Drops SPF 35. Both are great options if you need maximum protection with good transparency on all skin tones.
Why Do you Use Such High Concentrations of Zinc Oxide?
Some brands claim that coatings, dispersions, or “Super-Zinc” technologies mean you can get the same protection with less zinc oxide. But concentration still matters.
We use a simple rule of thumb:
Estimated SPF = % zinc oxide × 2
Estimated UVA-PF = % zinc oxide ÷ 2
Our research shows many sunscreens claim far higher SPFs than their zinc oxide content would suggest—often by adding SPF boosters or redness-reducing ingredients like niacinamide, aloe, or bisabolol. While these make formulas look good in testing, they don’t provide the same true UV absorption.
That’s why we stick to over 20% zinc oxide in every formula. It’s harder to formulate, but it ensures reliable broad-spectrum protection.
We created our Ava Isa line of mineral sunscreens to contain the maximum 25% of zinc oxide with no ‘chemical’ SPF boosters like butyloctyl salicylates or tridecyl salicylates. We do not use anti-redness/erythema SPF boosters like bisabolol or any similar type ingredient. We offer real protection with high UVA protection for your best daily mineral option.
Does it matter how much of an active ingredient is used in your sunscreen formula? Does the concentration Even Matter?
Pick up your all-mineral sunscreen and you'll see formulas with 25% zinc oxide and some with 2% zinc oxide. Why is there such a range or difference between different formulas? Can 2% zinc oxide ever be the same as 25%? Most consumers focus on the labelled SPF of a product and if both concentrations of the UV filter can give similar SPF’s then clearly there is no meaningful difference between the 2% vs the 25%. Brands and formulators have taken advantage of consumer confusion in thinking that the concentration of their zinc oxide does not matter.
There are always formulation considerations that can impact the efficacy and efficiency of the UV filter used in your sunscreen. The efficiency of your UV filter, i.e. how much UV light is attenuated for every 1% concentration, is definitely impacted by final formulation considerations. For example, considerations like the formulation system used, the impact of photo-stability of certain ingredients can improve or reduce the efficiency of your UV filter. (Hanay/Osterwalder, Challenges in Formulation).
Logically, it only makes sense that sunscreens are bound by the same laws of chemistry as any other product on Earth. Drugs like Tylenol or Aspirin are dosed with active ingredients according to a margin of safety and efficacy, i.e. a 5 mg dose of acetaminophen is not the same as 500 mg. Sunscreens formulas are no different.
There are established industry benchmarks for estimating the amount of protection a UV filter can provide. It is also fairly well understood within the industry about which parts of the UV spectrum an individual UV filter can cover. For example, titanium dioxide can protect against UVB and some short wave UVA (UVAII) depending on particle size. However, there is no current evidence that shows that it can ever protect against long wave UVA (UVAI) sufficiently.
If we are focusing on all-mineral sunscreens that exclusively contain zinc oxide, there are established industry benchmarks that have scientific evidence to determine approximately how much protection of the UV spectrum can be achieved for every single percentage of zinc oxide concentration. Every 1% of zinc oxide can provide 1.4 spf points of protection against the UVB and UVAI wavelengths, and 1.2 SPF points of protection against the UVAI and Visible light wavelengths. These chemistry standards allow us to determine the approximate amount of protection we can expect depending on the concentration of zinc oxide we include in our sunscreen formulas.
This means that if you see a sunscreen with a zinc oxide concentration of 12% you could conservatively expect a SPF rating of 16.8. If you are seeing higher SPF ratings than it should be, the formulators of that sunscreen are most likely using chemical SPF boosters to artificially game the SPF test to score a higher rating that what it’s protection level truly is.
We actually conducted a case study on this topic if you would like to learn more and see the breakdown of the data we tested, check out the study here: Understanding SPF Boosters in Mineral Sunscreens — The Sunscreen Company
What’s the difference With SPF vS Zinc Oxide Concentration?
Labelled SPF and consumer perception of a sunscreen's efficacy
Most consumers still judge the efficacy of a sunscreen by its labelled SPF. It's one of the few pieces of information available to consumers that is clear and concise and consumers use it accordingly.
There are well-established limitations to exclusively focusing on a sunscreen's SPF:
SPF is derived using an in-vivo (on human) test that has been shown to be highly inaccurate. Interlaboratory variability has been shown to be anywhere from 30-50% for any tested SPF (Miksa, Lutz et al, Sunscreen Sun Protection Factor claim based on in vivo interlaboratory variability). This means that one lab could test a formula as an SPF 30 and another could test the same formula as an SPF 45.
SPF does not measure protection against long wave UVA. UVA light accounts for about 95% of the UV light that hits Earth and yet the test that measures SPF eliminates most of UVA from the solar simulating device. SPF relates mostly against a sunscreens ability to protect against sunburn and some forms of skin cancer but not against UVA light that causes pigmentation, signs of skin aging and common forms of skin cancer. In North America especially due to weaker UVA related regulations, a sunscreen can have a high SPF but relatively weak UVA protection (.
With consumers's focus on SPF, many sunscreen formulators also focus on maximizing the labeled SPF of their formula. It can very challenging to do this while balancing considerations of cost, formula aesthetics and stability. Formulators have to weigh the options of using different UV filters to cover different parts of the UV spectrum (UVB, UVAII and UVAI) and how much of each filter to use.
Are newer Chemical Filters Better Than Zinc Oxide Now?
Korean and European sunscreens are often praised for using “next-gen” UV filters not available in North America. While some of these filters (like MBBT or BEMT) are excellent, not all are created equal—and many still lack the FDA’s GRASE designation (Generally Recognized as Safe and Effective).
By contrast, zinc oxide and titanium dioxide remain the only UV filters officially recognized as safe and effective by the FDA. Zinc oxide, in particular, provides unmatched broad-spectrum protection, is non-irritating, and does not absorb into the body.
Innovation is exciting, but zinc oxide has been continually refined for decades. Today’s zinc oxide mineral sunscreensare elegant, effective, and proven safe—making them a world-class choice for daily protection.
Are your Zinc Oxide sunscreens safe for pregnant women or breastfeeding women to use?
Yes! We take possible Endocrine Disruption very seriously and only work with filters that are large in size and are controversy free. Our co-founder a retired OB-GYN with a speciality in fetal maternal health and endocrinology shares his expertise with us to ensure we bring you the safest and most effective sunscreens for all phases in life. We actually use the litmus test for all of our research and development that our products should be ‘safe enough for a pregnant woman to use’ and we take a conservative approach in recommending any products that might be considered in a grey area.