What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Water
Skin ConditioningZinc Oxide
Cosmetic ColorantIsododecane
EmollientOctocrylene
UV AbsorberButyloctyl Salicylate
Skin ConditioningPropanediol
SolventTitanium Dioxide
Cosmetic ColorantDimethicone
EmollientDipropylene Glycol
HumectantEthylhexyl Salicylate
UV AbsorberPEG-10 Dimethicone
Skin ConditioningNiacinamide
SmoothingCaprylyl Methicone
Skin ConditioningDisteardimonium Hectorite
StabilisingCI 77891
Cosmetic ColorantDimer Dilinoleyl Dimer Dilinoleate
EmollientMagnesium Sulfate
1,2-Hexanediol
Skin ConditioningCaprylic/Capric Glycerides
EmollientTriethoxycaprylylsilane
Aluminum Hydroxide
EmollientPolyglyceryl-2 Dipolyhydroxystearate
Skin ConditioningC30-45 Alkyl Cetearyl Dimethicone Crosspolymer
EmollientGlycerin
HumectantStearic Acid
CleansingParfum
MaskingButylene Glycol
HumectantLauryl PEG-9 Polydimethylsiloxyethyl Dimethicone
Skin ConditioningAdenosine
Skin ConditioningHydrogenated Lecithin
EmulsifyingDiospyros Kaki Leaf Extract
Skin ProtectingVitis Vinifera Fruit Extract
Skin ConditioningCentella Asiatica Extract
CleansingFicus Carica Fruit Extract
HumectantCarthamus Tinctorius Flower Extract
Skin ConditioningCoffea Arabica Seed Extract
MaskingPolygonum Cuspidatum Root Extract
AntioxidantCamellia Sinensis Leaf Extract
AntimicrobialCastanea Crenata Bark Extract
Zanthoxylum Schinifolium Leaf Extract
Skin ConditioningSodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer
Emulsion StabilisingSelaginella Lepidophylla Extract
EmollientCI 77492
Cosmetic ColorantHydrogenated Poly(C6-14 Olefin)
EmollientCI 77491
Cosmetic ColorantCeramide NP
Skin ConditioningSalvia Hispanica Seed Extract
EmollientHouttuynia Cordata Extract
Skin ConditioningBakuchiol
AntimicrobialBenzyl Alcohol
PerfumingCI 77499
Cosmetic ColorantLauryl Glucoside
CleansingTocopherol
AntioxidantWater, Zinc Oxide, Isododecane, Octocrylene, Butyloctyl Salicylate, Propanediol, Titanium Dioxide, Dimethicone, Dipropylene Glycol, Ethylhexyl Salicylate, PEG-10 Dimethicone, Niacinamide, Caprylyl Methicone, Disteardimonium Hectorite, CI 77891, Dimer Dilinoleyl Dimer Dilinoleate, Magnesium Sulfate, 1,2-Hexanediol, Caprylic/Capric Glycerides, Triethoxycaprylylsilane, Aluminum Hydroxide, Polyglyceryl-2 Dipolyhydroxystearate, C30-45 Alkyl Cetearyl Dimethicone Crosspolymer, Glycerin, Stearic Acid, Parfum, Butylene Glycol, Lauryl PEG-9 Polydimethylsiloxyethyl Dimethicone, Adenosine, Hydrogenated Lecithin, Diospyros Kaki Leaf Extract, Vitis Vinifera Fruit Extract, Centella Asiatica Extract, Ficus Carica Fruit Extract, Carthamus Tinctorius Flower Extract, Coffea Arabica Seed Extract, Polygonum Cuspidatum Root Extract, Camellia Sinensis Leaf Extract, Castanea Crenata Bark Extract, Zanthoxylum Schinifolium Leaf Extract, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Selaginella Lepidophylla Extract, CI 77492, Hydrogenated Poly(C6-14 Olefin), CI 77491, Ceramide NP, Salvia Hispanica Seed Extract, Houttuynia Cordata Extract, Bakuchiol, Benzyl Alcohol, CI 77499, Lauryl Glucoside, Tocopherol
Water
Skin ConditioningCyclomethicone
EmollientEthylhexyl Methoxycinnamate
UV AbsorberMica
Cosmetic ColorantC12-15 Alkyl Benzoate
AntimicrobialDipropylene Glycol
HumectantGlycerin
HumectantZinc Oxide
Cosmetic ColorantCI 77891
Cosmetic ColorantPEG-10 Dimethicone
Skin ConditioningMethyl Trimethicone
Skin ConditioningTitanium Dioxide
Cosmetic ColorantCI 77007
Cosmetic ColorantEthylhexyl Salicylate
UV AbsorberDimethicone
EmollientButylene Glycol
HumectantDisteardimonium Hectorite
StabilisingCI 77492
Cosmetic ColorantMagnesium Sulfate
Centella Asiatica Extract
CleansingGlycyrrhiza Glabra Root Extract
BleachingTalc
AbrasiveVinyl Dimethicone/Methicone Silsesquioxane Crosspolymer
Dimethicone/Vinyl Dimethicone Crosspolymer
Skin ConditioningAluminum Hydroxide
EmollientTrihydroxystearin
Skin ConditioningMethicone
EmollientPalmitic Acid
EmollientPolyester-1
Stearic Acid
CleansingSilica Dimethyl Silylate
EmollientTocopheryl Acetate
AntioxidantEthylhexylglycerin
Skin ConditioningTin Oxide
AbrasivePhenoxyethanol
PreservativeParfum
MaskingHexyl Cinnamal
PerfumingAlpha-Isomethyl Ionone
PerfumingLinalool
PerfumingCitronellol
PerfumingGeraniol
PerfumingEugenol
PerfumingLimonene
PerfumingCI 77491
Cosmetic ColorantCI 77499
Cosmetic ColorantWater, Cyclomethicone, Ethylhexyl Methoxycinnamate, Mica, C12-15 Alkyl Benzoate, Dipropylene Glycol, Glycerin, Zinc Oxide, CI 77891, PEG-10 Dimethicone, Methyl Trimethicone, Titanium Dioxide, CI 77007, Ethylhexyl Salicylate, Dimethicone, Butylene Glycol, Disteardimonium Hectorite, CI 77492, Magnesium Sulfate, Centella Asiatica Extract, Glycyrrhiza Glabra Root Extract, Talc, Vinyl Dimethicone/Methicone Silsesquioxane Crosspolymer, Dimethicone/Vinyl Dimethicone Crosspolymer, Aluminum Hydroxide, Trihydroxystearin, Methicone, Palmitic Acid, Polyester-1, Stearic Acid, Silica Dimethyl Silylate, Tocopheryl Acetate, Ethylhexylglycerin, Tin Oxide, Phenoxyethanol, Parfum, Hexyl Cinnamal, Alpha-Isomethyl Ionone, Linalool, Citronellol, Geraniol, Eugenol, Limonene, CI 77491, CI 77499
Ingredients Explained
These ingredients are found in both products.
Ingredients higher up in an ingredient list are typically present in a larger amount.
Aluminum Hydroxide is a form of aluminum. It can be naturally found in nature as the mineral gibbsite. In cosmetics, Aluminum Hydroxide is used as a colorant, pH adjuster, and absorbent.
As a colorant, Aluminum Hydroxide may add opacity, or reduce the transparency. Aluminum hydroxide is contains both basic and acidic properties.
According to manufacturers, this ingredient is an emollient and humectant. This means it helps hydrate the skin.
In medicine, this ingredient is used to help relieve heartburn and help heal ulcers.
There is currently no credible scientific evidence linking aluminum hydroxide in cosmetics to increased cancer risk.
Major health organizations allow the use of aluminum hydroxide in personal care products and have not flagged it as a carcinogenic risk at typical usage levels.
Learn more about Aluminum HydroxideButylene Glycol (or BG) is used within cosmetic products for a few different reasons:
Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.
Though this ingredient works well with most skin types, some people with sensitive skin may experience a reaction such as allergic rashes, closed comedones, or itchiness.
Learn more about Butylene GlycolCentella Asiatica Extract (Centella) is one of the most researched botanical extracts in skincare with decades of studies backing its effects on inflammation, collagen, and the skin barrier.
That research keeps pointing back to the same four triterpenoid saponins: Asiaticoside, Madecassoside, Asiatic Acid, and Madecassic Acid.
These compounds allow centella to dial back inflammation, encourage the skin to build and hold onto collagen, support the barrier and hydration, and bring solid antioxidant activity to protect against signs of aging.
Centella also carries a nice supporting cast of Vitamin A, vitamin C, several B vitamins, and amino acids. Put it all together and you get an ingredient that soothes, hydrates, and protects, all at once.
Most of centella's magic comes from the four big compounds (Asiaticoside, Madecassoside, Asiatic Acid, and Madecassic Acid). These are the actives doing the heavy lifting in almost every centella study.
Here is the short version of what they do in the skin:
So it is not just soothing for the sake of soothing. Centella calms the skin AND helps it rebuild.
Just FYI, not all centella on an ingredient list is the same. What you are getting actually depends on the extract:
Fun fact on the ratios: the leaves tend to be richest in Madecassoside and Asiaticoside, and lower in the two acids. The exact amounts shift with where the plant is grown and how it is processed. This means purity really does vary brand to brand.
Centella is one of the most easygoing actives out there.
It layers well with basically everything: niacinamide, hyaluronic acid, peptides, and vitamin C, and also pairs nicely with stronger actives like retinoids and exfoliating acids where it can help take the edge off irritation.
On the safety side, centella and its triterpenes are classified as weak sensitizers, meaning allergic reactions are possible but uncommon.
Patch tests at 1% and 5% came back negative in test panels, and creams at typical use levels did not cause allergic reactions across large groups of people.
But as with any new active, a patch test is still a smart move for very reactive skin.
Centella is widely used because it is effective at low percentages. For context, human safety testing found no meaningful irritation from creams containing centella extract at everyday use levels (the tested amounts were well under 1%).
The irritancy threshold in animal testing was also above 30% (so real-world formulas sit far below anything concerning).
In collagen lab studies, higher concentrations drove more collagen synthesis, so serums built around centella tend to feature it more prominently.
Bottom line: you will find centella working nicely anywhere from a fraction of a percent up to hero-ingredient levels depending on whether it is a supporting soother or the main event.
Fun fact: Centella has been used as a medicine and in food for many centuries. As a medicine, it is used to treat burns, scratches, and wounds.
Learn more about Centella Asiatica ExtractCi 77491 is also hydrated iron III oxide. It's sole purpose is to give a red/pink hue to products.
Iron III oxides are classified as inorganic chemicals for coloring.
Synthetically created Ci 77491 is considered safer than those naturally found. This is because the synthetically created version may contain less impurities. Iron oxides are generally non-toxic and non-allergenic.
Learn more about CI 77491CI 77492 is also hydrated iron III oxide. It's sole purpose is to give a yellow hue to products.
Iron III oxides are classified as inorganic chemicals for coloring.
Synthetically created CI 77492 is considered safer than those naturally found. This is because the synthetically created version may contain less impurities. Iron oxides are generally non-toxic and non-allergenic.
Learn more about CI 77492Ci 77499 is also hydrated iron III oxide. It is created from mixing red and black iron oxides. This helps give shades of darkness to a product.
Iron III oxides are classified as inorganic chemicals for coloring.
Ci 77891 is a white pigment from Titanium dioxide. It is naturally found in minerals such as rutile and ilmenite.
It's main function is to add a white color to cosmetics. It can also be mixed with other colors to create different shades.
Ci 77891 is commonly found in sunscreens due to its ability to block UV rays.
Learn more about CI 77891Dimethicone is a type of synthetic silicone created from natural materials such as quartz. It is also known as polydimethylsiloxane.
What it does:
Dimethicone comes in different viscosities:
Depending on the viscosity, dimethicone has different properties.
Ingredients lists don't always show which type is used, so we recommend reaching out to the brand if you have questions about the viscosity.
This ingredient is unlikely to cause irritation because it does not get absorbed into skin. However, people with silicone allergies should be careful about using this ingredient.
Note: Dimethicone may contribute to pilling. This is because it is not oil or water soluble, so pilling may occur when layered with products. When mixed with heavy oils in a formula, the outcome is also quite greasy.
Learn more about DimethiconeDipropylene Glycol is a synthetically created humectant, stabilizer, and solvent.
This ingredient helps:
Dipropylene glycol is technically an alcohol, but it belongs to the glycol family (often considered part of the ‘good’ alcohols). This means it is hydrating and gentle on skin unlike drying solvent alcohols like denatured alcohol.
As a masking agent, Dipropylene Glycol can be used to cover the smell of other ingredients. However, it does not have a scent.
Studies show Dipropylene Glycol is considered safe to use in skincare.
Learn more about Dipropylene GlycolDisteardimonium Hectorite comes from the clay mineral named hectorite. It is used to add thickness to a product.
It can also help stabilize a product by helping to disperse other ingredients.
Hectorite is a rare, white clay mineral.
Learn more about Disteardimonium HectoriteEthylhexyl Salicylate (also called Octisalate or Octyl Salicylate) is an oil-soluble organic UV filter that's been used in sunscreen since the 1950's.
It absorbs UVB light in the 280-320 nm range with a peak absorbance around 306 nm.
You'll often see it paired with other UV filters to boost overall SPF because octisalate is a fairly week filter on its own.
The reason you'll see it so often is because it can help solubilize and stabilize the trickier filters like oxybenzone and avobenzone.
Unlike these filters, octisalate has pretty good photostability and doesn't create skin-damaging free radicals when exposed to sunlight.
The fatty-alcohol part of the molecule also gives it a light, emollient feel so it doubles as a nice texture enhancer.
Usage levels vary around the world:
Safety-wise, this ingredient has a pretty reassuring track record. The EU's Scientific Committee on Consumer Products (SCCP) found very low skin penetration in human skin tests and negative results for irritation, phototoxicity, and photoallergy.
The real-world allergy risk is pretty low too; a 2012 European study of 1,031 people recorded only 2 reactions to it (a rate of 0.19%).
You might have seen scary headlines about sunscreen getting into your blood.
In 2019, the FDA found that several chemical filters can absorb through the skin and show up in the bloodstream at small but measurable levels.
Here's the important part: these tiny levels are just a cutoff the FDA uses to decide which ingredients need more testing and doesn't mean anything harmful was found.
The researchers were clear that the results are no reason to stop wearing sunscreen.
Learn more about Ethylhexyl SalicylateGlycerin (or glycerol) is a compound naturally found in your skin. It's a powerhouse humectant that pulls water into the stratum corneum.
Topically, glycerin does several things at once:
Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.
Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.
This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.
Just know very high concentrations (>40%) can feel tacky in low humidity.
Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.
Learn more about GlycerinMagnesium Sulfate is a salt. More specifically, it is an epsom salt, or the bath salt used to help relieve muscle aches.
Despite having ‘sulfate’ in the name, it isn’t a surfactant or cleansing agent like sodium lauryl sulfate. Unlike those sulfates, magnesium sulfate doesn’t have the same cleansing or foaming properties (it's simply a type of salt).
In cosmetics, Magnesium Sulfate is used to thicken a product or help dilute other solids. It is a non-reactive and non-irritating ingredient.
One study shows magnesium deficiency may lead to inflammation of the skin. Applying magnesium topically may help reduce inflammation.
You can find this ingredient in sea water or mineral deposits.
Learn more about Magnesium SulfateParfum is a catch-all term for an ingredient or more that is used to give a scent to products.
Also called "fragrance", this ingredient can be a blend of hundreds of chemicals or plant oils. This means every product with "fragrance" or "parfum" in the ingredients list is a different mixture.
For instance, Habanolide is a proprietary trade name for a specific aroma chemical. When used as a fragrance ingredient in cosmetics, most aroma chemicals fall under the broad labeling category of “FRAGRANCE” or “PARFUM” according to EU and US regulations.
The term 'parfum' or 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term.
For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance by INCI standards.
One example is Calendula flower extract. Calendula is an essential oil that still imparts a scent or 'fragrance'.
Depending on the blend, the ingredients in the mixture can cause allergies and sensitivities on the skin. Some ingredients that are known EU allergens include linalool and citronellol.
Parfum can also be used to mask or cover an unpleasant scent.
The bottom line is: not all fragrances/parfum/ingredients are created equally. If you are worried about fragrances, we recommend taking a closer look at an ingredient. And of course, we always recommend speaking with a professional.
Learn more about ParfumPeg-10 Dimethicone is silicone with conditioner and emulsifier properties. It mostly acts as an emollient in skincare and and humectant in haircare.
According to the manufacturer, acidic formulations decrease the stability of this ingredient. It works best in neutral or near neutral formulations.
Stearic Acid is a fatty acid that is already found in your skin. It's one of the free fatty acids that works alongside ceramides and cholesterols to maintain your barrier.
In cosmetics, it is a multitasker:
Safety-wise, the CIR Expert Panel has concluded it to be safe in cosmetics when formulated to be non-irritating and non-sensitizing.
Free stearic acid is a C18 fatty acid that the Malassezia yeast can substrate, so this ingredient may not be fungal acne safe.
Learn more about Stearic AcidTitanium Dioxide (TD) is a mineral UV filter widely used in sunscreens and cosmetics.
It's one of only two UV filters officially classified as "mineral" by regulatory agencies (the other being Zinc Oxide).
A really common myth is that mineral filters work by reflecting UV light off your skin like tiny mirrors.
They don't only do that; modern research shows TD protects mostly by absorbing UV radiation, the same way chemical filters do.
When researchers measured this, reflection accounted for only about 4-5% of the protection (and less than SPF 2 on its own). The other ~95% comes from absorption: the UV photons hit the particle and their energy gets soaked up by its semiconductor band gap rather than bouncing off.
So "reflects vs. absorbs" was never really the right way to split mineral from chemical filters.
TD gives broad-spectrum protection that's strongest in the UVB and UVA-2 range and weaker in the UVA-1 range. Its UVA protection isn't quite as strong as Zinc Oxide's which is why you'll often see the two paired together.
Together, they make a solid broad-spectrum system.
TD is a great pick for sensitive, acne-prone, or redness-prone skin because it's non-irritating and chemically inert. Regulatory reviews classify it as a non-sensitizer and mild-to-non-irritant.
It's also unlikely to cause the "eye sting" some chemical filters are known for.
The main trade-off is cosmetic; TD can leave a white cast and has a thicker texture. This is why mineral sunscreens are often less cosmetically elegant than chemical or hybrid formulas (and harder to shade-match on deeper skin tones).
Formulators often use micronized or nano-sized TD to cut down on white case and improve spreadability. Smaller particles scatter less visible light so the formula looks less chalky while still filtering UV.
TD is almost always bundled with coatings like Alumina, Silica, Stearic Acid, or Dimethicone. These coatings do two important jobs:
TD can be used at up to 25% in a finished sunscreen; this is the regulatory ceiling in both the US and the EU.
In practice, the amount in any given product varies a lot depending on the target SPF and whether it's paired with other UV filters.
TD is one of the most heavily vetted sunscreen ingredients out there. It is approved as a UV filter in all major markets worldwide, including the US, EU, UK, Japan, Korea, China, Australia, and Canada.
The safety evidence is solid. There was an old worry that nano particles might absorb through skin into the body but multiple studies (including on damaged, sunburned, and UV-irradiated skin) have shown that TD stays on the surface and the layer of dead skin cells on top of everything else.
There's also no evidence of carcinogenicity, mutagenicity, or reproductive toxicity from dermal exposure of this ingredient.
For those who have seen the headline about a 2022 EU ban on TD, that was on TD as a food additive (a complete separate use from topical sunscreen).
There are ongoing questions about how nano-TD might affect marine ecosystems. As of now, there has been no conclusive evidence that any form of TD (or any other sunscreen filter) harms coral reefs or marine life.
The science is still developing and it's a space worth watching rather than packing over.
However, several destinations have reef-safety sunscreen rules that restrict certain chemical filters and steer visitors toward mineral, non-nano options. If you're traveling somewhere with these rules, a non-nano mineral sunscreen is the safe bet.
Learn more about Titanium DioxideWater. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.
So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.
You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!
Learn more about WaterZinc Oxide (ZO) is a mineral broad-spectrum UV filter and the broadest-spectrum filter recognized by the FDA. It covers everything from UVB through to long-wave UVA.
On top of sun protection, it has skin protectant and skin-soothing properties too.
Here's a myth worth busting: mineral filters are usually described as working by "reflecting" or "bouncing" UV off your skin.
That's mostly not true: when researchers actually measured it, ZO and Titanium Dioxide reflect only about 4-5% of UV (less than SPF 2 worth of protection).
The vast majority of the work (~95%) is done by absorption, similar to chemical UV filters. ZO is a semiconductor that absorbs UV photos through its energy band gap.
So the old "physical blocker vs. chemical absorber" framing is really an oversimplification.
Zinc Oxide is one of the most effective broad-spectrum UV filters out there. It protects across UVB, UVA2, and UVA1 with a flat, even absorption curve across the whole UVA-UVB range.
That uniform UVA coverage is its standout feature; titanium dioxide skews more toward UVB as its particle size drops so ZO gives more consistent and extended UVA protection.
It's also very photostable. As an inorganic oxide, ZO doesn't break down in sunlight the way some organic filters can, so it holds up over a day of wear.
This ingredient is gentle and soothing, making it go-to for sunscreens aimed at sensitive skin, rosacea, or ecezma-prone skin, babies, and children.
It's also unlikely to cause the "eye sting" that some sunscreen ingredients are known for, and regulatory agencies broadly consider it non-toxic and safe for topical use.
Beyond sun protection, ZO is also a recognized OTC skin protectant. It forms a breathable barrier that shields skin from moisture and irritation while supporting healing. This is why you'll see it as a classic active in diaper rash creams.
The only downside to ZO is that it can leave a visible white cast, especially on deeper skin tones. This is the main reason mineral sunscreens have historically felt less cosmetically elegant than chemical or hybrid formulas.
Zinc Oxide comes in both non-nano and nano forms. The dividing line is 100nm and anything under is classified as a nanomaterial by the EU.
The nano version scatters less visible light which cuts down white case and gives a lighter, more wearable texture.
Another thing worth understanding about formulation:
Uncoated ZO has some inherent photocatalytic activity. This just means it can generate reactive oxygen species under UV. It's exactly why cosmetic-grade ZO is almost always surface-coated; this coating suppresses that reactivity and improves how the powder disperses and feels.
A well-formulated coated ZO largely sidesteps this issue.
Zinc Oxide is commonly used anywhere from 10% up to the regulatory maximum in sunscreens (25%).
Mineral-only broad-spectrum products often land in the 15-25% range to hit higher SPF and UVA values. Keep in mind SPF performance depends heavily on particle size, dispersion, and the rest of the formula, and not just the percentage.
As an OTC skin protectant like diaper creams, ZO typically runs higher at roughly 10-40%.
This ingredient is generally easy to work with and doesn't photodegrade.
The only thing to know is that uncoated ZO can be a bit reactive in a formula.
Under UV, it can break down sensitive ingredients like other actives or UV filters. This is another reason coated versions are standard. ZO can also react with very acidic ingredients or throw off stability of some creams. A good formula will get around this with the right coatings and dispersion.
The EU's Scientific Committee on Consumer Safety has concluded that ZO nanoparticles "can be considered to not pose any risk of adverse effects in humans after application on healthy, intact or sunburnt skin".
You might hear that ZO is "toxic"; this is because an in-vitro (test tube) study suggested micronized ZO had potential phototoxicity. In vivo (human) investigations have disputed this and the results have come back reassuring.
So does ZO penetrate skin? The short answer is no, not in any way that matters.
The most relevant evidence comes from real-world human studies: in one, volunteers applied ZO nanoparticle sunscreen hourly for six hours and daily for five days. The advanced imaging showed the particles stayed on the surface and never reached the living epidermis, and no cellular toxicity was found.
Other in-vivo and ex-vivo work agree; ZO nanoparticles don't cross the stratum corneum, even on flexed, massaged, or barrier-impaired skin.
A small amount of solubilized zinc ions can dissolve off the particles and enter the upper skin. But the quantities are tiny compared to the zinc already naturally present in your body, and studies haven't found this to cause local toxicity.
The sunscreen bans you've heard of (like Hawaii's) are aimed at two chemical filters, Oxybenzone and Octinoxate. ZO itself it not banned and is often recommended instead.
So far, there's no solid evidence that any form of ZO harms reefs. It is an ongoing and active area of study, and worth keeping an eye on.
If you're traveling somewhere with these rules, a non-nano mineral sunscreen is the safe bet.
Learn more about Zinc Oxide