What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Ethylhexyl Methoxycinnamate
UV AbsorberBis-Ethylhexyloxyphenol Methoxyphenyl Triazine
Skin ConditioningMethoxyphenylbutanone
PerfumingButyl Methoxydibenzoylmethane
UV AbsorberOctocrylene
UV AbsorberTitanium Dioxide
Cosmetic ColorantZinc Oxide
Cosmetic ColorantMelaleuca Alternifolia Leaf Oil
AntioxidantCocos Nucifera Oil
MaskingSulfur
AntiseborrhoeicSalicylic Acid
MaskingLactic Acid
BufferingNiacinamide
SmoothingSodium Hyaluronate
HumectantButyrospermum Parkii Butter
Skin ConditioningCamellia Sinensis Leaf Extract
AntimicrobialDibutyl Adipate
EmollientAscorbic Acid
AntioxidantCopernicia Cerifera Cera
EmollientChamomilla Recutita Extract
Skin ConditioningBisabolol
AntioxidantAllantoin
Skin ConditioningOctyldodecyl Neopentanoate
EmollientDecyl Oleate
EmollientPEG-7 Glyceryl Cocoate
EmulsifyingC12-15 Alkyl Benzoate
AntimicrobialTocopheryl Acetate
AntioxidantCetearyl Alcohol
EmollientGlyceryl Stearate
EmollientCeteareth-20
CleansingTriethanolamine
BufferingXanthan Gum
EmulsifyingIsopropyl Palmitate
EmollientCyclomethicone
EmollientPanthenol
Skin ConditioningAlcohol Denat.
AntimicrobialGlycerin
HumectantPropylene Glycol
HumectantDimethicone
EmollientCitric Acid
BufferingCentella Asiatica Extract
CleansingPolysorbate 80
EmulsifyingPhenoxyethanol
PreservativeWater
Skin ConditioningEthylhexyl Methoxycinnamate, Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Methoxyphenylbutanone, Butyl Methoxydibenzoylmethane, Octocrylene, Titanium Dioxide, Zinc Oxide, Melaleuca Alternifolia Leaf Oil, Cocos Nucifera Oil, Sulfur, Salicylic Acid, Lactic Acid, Niacinamide, Sodium Hyaluronate, Butyrospermum Parkii Butter, Camellia Sinensis Leaf Extract, Dibutyl Adipate, Ascorbic Acid, Copernicia Cerifera Cera, Chamomilla Recutita Extract, Bisabolol, Allantoin, Octyldodecyl Neopentanoate, Decyl Oleate, PEG-7 Glyceryl Cocoate, C12-15 Alkyl Benzoate, Tocopheryl Acetate, Cetearyl Alcohol, Glyceryl Stearate, Ceteareth-20, Triethanolamine, Xanthan Gum, Isopropyl Palmitate, Cyclomethicone, Panthenol, Alcohol Denat., Glycerin, Propylene Glycol, Dimethicone, Citric Acid, Centella Asiatica Extract, Polysorbate 80, Phenoxyethanol, Water
Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine
Skin ConditioningTris-Biphenyl Triazine
UV AbsorberDibutyl Adipate
EmollientDiethylamino Hydroxybenzoyl Hexyl Benzoate
UV FilterEthylhexyl Methoxycinnamate
UV AbsorberEthylhexyl Triazone
UV AbsorberLaureth-7 Citrate
CleansingLauryl Glucoside
CleansingPolyglyceryl-2 Dipolyhydroxystearate
Skin ConditioningTriethanolamine
BufferingIsobutylamido Thiazolyl Resorcinol
BleachingGlycyrrhiza Inflata Root Extract
Skin ConditioningTocopherol
AntioxidantGlabridin
BleachingTitanium Dioxide
Cosmetic ColorantZinc Oxide
Cosmetic ColorantCarbomer
Emulsion StabilisingAscorbyl Palmitate
AntioxidantChamomilla Recutita Flower Extract
MaskingPanthenol
Skin ConditioningAllantoin
Skin ConditioningPEG-7 Glyceryl Cocoate
EmulsifyingDecyl Oleate
EmollientGlycerin
HumectantPropylene Glycol
HumectantOctyldodecanol
EmollientCocos Nucifera Oil
MaskingButyrospermum Parkii Butter
Skin ConditioningDaucus Carota Sativa Seed Oil
EmollientPhenoxyethanol
PreservativeGlyceryl Stearate
EmollientXanthan Gum
EmulsifyingWater
Skin ConditioningBis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Tris-Biphenyl Triazine, Dibutyl Adipate, Diethylamino Hydroxybenzoyl Hexyl Benzoate, Ethylhexyl Methoxycinnamate, Ethylhexyl Triazone, Laureth-7 Citrate, Lauryl Glucoside, Polyglyceryl-2 Dipolyhydroxystearate, Triethanolamine, Isobutylamido Thiazolyl Resorcinol, Glycyrrhiza Inflata Root Extract, Tocopherol, Glabridin, Titanium Dioxide, Zinc Oxide, Carbomer, Ascorbyl Palmitate, Chamomilla Recutita Flower Extract, Panthenol, Allantoin, PEG-7 Glyceryl Cocoate, Decyl Oleate, Glycerin, Propylene Glycol, Octyldodecanol, Cocos Nucifera Oil, Butyrospermum Parkii Butter, Daucus Carota Sativa Seed Oil, Phenoxyethanol, Glyceryl Stearate, Xanthan Gum, Water
Reviews
Ingredients Explained
These ingredients are found in both products.
Ingredients higher up in an ingredient list are typically present in a larger amount.
Allantoin is a soothing ingredient known for its protective and moisturizing properties; it's basically a quiet workhorse ingredient you can find in a huge range of cosmetics.
Though it can be derived from the comfrey plant, allantoin is produced synthetically for cosmetic products to ensure purity.
Research shows it can encourage your skin cells to turn over and renew by stimulating keratinocyte and fibroblast proliferation.
It also has mild keratolytic properties to help loosen and shed dead skin cells without being harsh.
Studies also suggest allantoin can help calm inflammation by dialing down some of the chemical signals your skin sends out when it is irritated.
This ingredient is typically used in the 0.1-0.5% range, and the FDA recognizes it as a skin protectant in OTC products up to 2%.
Overall, allantoin is a wonderful addition to most routines; it is stable across a wide pH range (~4-8), works well with other ingredients, and is considered non-sensitizing/non-irritating.
Fun fact: Allantoin is naturally occurring in comfrey root, beets, chamomile, and wheat sprouts. Our bodies even produce it as a byproduct of uric acid metabolism.
Learn more about AllantoinThis ingredient is better known as bemotrizinol or Tinosorb S and is one of the best broad-spectrum UV filters in modern sunscreen.
It works by absorbing UV light across a whole range (280-400 nm) with peaks around 310 nm (UVB) and 340-345 nm (UVA). This means it covers UVB plus the deeper UVA wavelengths that drive photoaging and pigmentation.
Another pro?
It's exceptionally photostable, barely degrades in sunlight, and acts as a "bodyguard" for less stable filters.
That's why you'll see it paired with avobenzone or octinoxate; this team up ensures they keep working through sun exposure.
Safety reviews have been reassuring across the board. This ingredient shows low absorption through the skin, rarely irritates, and lab studies found it doesn't act like a hormone in the body (a concern that's been raised about some older sunscreen filters).
On maximum concentrations:
In 2026, the US F.D.A finally added it as an OTC sunscreen ingredient at concentrations up to 6% for adults / children 6 months and older
Learn more about Bis-Ethylhexyloxyphenol Methoxyphenyl TriazineThis ingredient is also known as shea butter. It is a plant-derived extract from the nuts of the Africa shea tree and one of the most well-studied emollients.
Because it has a high concentration of fatty acids (primarily oleic, stearic, and linoleic) it is able to form a protective barrier on the skin's surface. This helps seal in moisture and prevents transepidermal water loss (TEWL).
In vitro research found an increase in skin hydration by 58% and a decrease in TEWL by 37.8% after 24 hours of applying this ingredient (pretty impressive for a single ingredient!).
Besides hydration, shea butter also contains triterpenes that have anti-inflammatory potential. In particule, lupeol cinnamate has shown the highest anti-inflammatory activity in vivo.
Shea butter also contains vitamins A and E which may contribute to antioxidant activity.
While Shea Butter has an SPF rating of about 3-4, it is not a sunscreen replacement.
This ingredient may not be fungal acne safe because its fatty acids fall within the C11-C24 range that the Malassezia yeast can metabolize.
Learn more about Butyrospermum Parkii ButterThis ingredient is also known as coconut oil. It is a plant-derived ingredient with skin conditioning properties.
The fatty acid profile of coconut oil is mostly lauric acid (~54%), followed by capric, caprylic, palmitic, and myristic acids. This profile allows it to penetrate easily into skin, moisturize, and improve dry skin.
A double-blind study confirmed that extra virgin coconut oil is as effective as mineral oil for treating very dry skin. Another study found it outperformed mineral oil for mild to moderate atopic dermatitis in children.
Another study from 2018 found that virgin coconut oil can soothe inflammation and boost key skin barrier proteins. Just know this evidence is still only from lab settings and not human trials.
It has also been shown to reduce Staphylococcus aureus, a bacteria that commonly overgrows in people with eczema.
Clinical testing shows very minimal skin irritation and no evidence of sensitization or phototoxicity.
Coconut oil gets flagged as a "fragrance" because it has a natural mild scent (not because it's a synthetic perfume). The European Cosmetic ingredient database also lists "perfuming" as a function of this ingredient.
Just so you know, the term "fragrance" is completely unregulated. Some brands still use botanical extracts or essential oils in their "fragrance-free" formulas, but regulatory databases technically classify these under "fragrance".
Coconut oil has a tiny and useless bit of natural SPF. Early lab studies clocked it around SPF 7-8 but a more recent study found the real number closer to SPF 1.2. It also offers no meaningful UVA protection (SPF only overs UVB rays).
The comedogenic rating of 4/5 means it has a high potential to clog pores; but it's worth noting that comedogenicity is highly individual and ratings cannot predict how an overall formula will behave on skin.
Since lauric acid is the dominant fatty acid, this ingredient may not be fungal acne safe. The Malassezia yeast feeds on fatty acids with carbon chain lengths between 11-24, and lauric acid falls within these lengths (C12).
Learn more about Cocos Nucifera OilDecyl Oleate comes from decyl alcohol and oleic acid.
Decyl Oleate is an emollient. It helps moisturize the skin by creating a thin barrier on top to prevent moisture from escaping.
This ingredient may not be fungal-acne safe.
Learn more about Decyl OleateDibutyl Adipate is a lightweight, oil-soluble ester that acts as an emollient and solvent. It helps products spread more easily and leaves a soft, silky, dry-touch finish without being greasy.
You'll likely see this ingredient in sunscreens because it does a nice job dissolving UV filters and keeping them evenly distributed.
This ingredient has been found to be safe as used in cosmetics, wasn't a skin or eye irritant in clinical patch testing, and wasn't phototoxic.
In a clinical comedogenicity test, this ingredient tested negative so it isn't likely to clog pores.
Typical use levels are about 5-8% for sunscreens + nail products, but can range from 0.005%-8% depending on the product.
Learn more about Dibutyl AdipateThis ingredient is also known as Octinoxate and is one of the oldest and most widely used chemical UV filters in skincare.
It has a simple job: soap up UVB radiation (290-320 nm), the wavelengths responsible for sunburn and a big chunk of long-term sun damage.
In formulas, it's always paired with a separate UVA filter because octinoxate solely protects skin from UVB.
Because it's an oil-soluble liquid, it's easy to blend into the oil phase of lotions/creams and gives a cosmetically elegant feel.
The one quirk about formulating this ingredient is photostability; the molecule slowly changes shape into a less effective version when sunlight hits it. So the longer you're in the sun, the weaker its protection gets. The drop can be more than 30% in some formulas.
It also doesn't play nice with Avobenzone (the common UVA filter) since avobenzone destabilizes octinoxate and the two degrade each other. But don't worry: brands have solved this issue by adding photostabilizers like Tinosorb S to prevent degradation and keep SPF stable under heavy UV exposure.
The maximum allowed level is 10% in the EU and Australia, 7.5% in the US and Canada, and 20% in Japan.
The Cosmetic Ingredient Review Panel has concluded this ingredient to be safe in cosmetics up to 10%.
One last thing worth knowing for context:
Octinoxate has been the subject of ongoing review in Europe where the Scientific Committee on Consumer Safety's (SCCS) 2025 final opinion is that this ingredient is an endocrine-active substance.
Lab and animal studies suggest it can act a bit like a hormone in the body (mildly mimicking estrogen and slightly blocking male hormones). It's important to know this hasn't really been shown to happen in everyday human use.
This ingredient is also banned in Hawaii over coral reef concerns.
Learn more about Ethylhexyl MethoxycinnamateGlycerin (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 GlycerinGlyceryl Stearate is made by reacting glycerin with stearic acid (typically sourced from plant oils like palm or coconut). It's an emulsifier, emollient, and mild occlusive.
Emulsifiers help ingredients like oil and water stay mixed so your formula stays nicely blended and uniform in texture.
This ingredient is typically used in concentrations between 1-10%. Studies have found it to be non-sensitizing, non-phototoxic, and non-photoallergenic.
A close cousin of this ingredient is Glyceryl Stearate SE ("self-emulsifying"). This just has a small amount of sodium or potassium stearate added so it can emulsify without a co-emulsifier.
Since this ingredient is an ester of a C18 fatty acid, it may not be fungal acne safe. The Malassezia yeast can potentially metabolize within the C11-C24 range.
Fun fact: The human body also creates Glyceryl Stearate naturally.
Learn more about Glyceryl StearatePanthenol is a common ingredient that helps hydrate and soothe the skin. It is found naturally in our skin and hair.
There are two forms of panthenol: D and L.
D-panthenol is also known as dexpanthenol. Most cosmetics use dexpanthenol or a mixture of D and L-panthenol.
Panthenol is famous due to its ability to go deeper into the skin's layers. Using this ingredient has numerous pros (and no cons):
Like hyaluronic acid, panthenol is a humectant. Humectants are able to bind and hold large amounts of water to keep skin hydrated.
This ingredient works well for wound healing. It works by increasing tissue in the wound and helps close open wounds.
Once oxidized, panthenol converts to pantothenic acid. Panthothenic acid is found in all living cells.
This ingredient is also referred to as pro-vitamin B5.
Learn more about PanthenolPEG-7 Glyceryl Cocoate is a synthetic, water-soluble surfactant and emulsifier.
It's a "superfatting" agent that helps replenish some of your skin's oils after they're stripped away by other surfactants.
This is why "gentle" and "moisturizing" cleansers feel less stripping than basic ones.
Typical concentrations range from 1-10% and it has a solid safety record. The CIR Expert Panel has concluded this ingredient to be safe at concentrations up to 10% in leave-on products.
Dermal application tests at 50% also did not produce irritation in two studies.
This ingredient may not be fungal acne safe and in vitro studies have shown Malassezia can metabolize it.
Learn more about PEG-7 Glyceryl CocoatePhenoxyethanol is a preservative that has germicide, antimicrobial, and aromatic properties. Studies show that phenoxyethanol can prevent microbial growth. By itself, it has a scent that is similar to that of a rose.
It's often used in formulations along with Caprylyl Glycol to preserve the shelf life of products.
Propylene Glycol is a synthetic, colorless, odorless liquid that has been a staple in cosmetics for decades. It is a skin conditioning agent, humectant, and solvent.
As a humectant, it draw water to the skin to reduce flaking and restore suppleness. It's also a solvent that helps dissolve other actives and keeps formulas stable across temperature changes.
The CIR Expert Panel has confirmed this ingredient to be nontoxic and clinical studies show no sensitization at cosmetic use concentrations.
True allergic reactions are quite rare: a 15-year retrospective study of 6,751 patients found only 0.31% had a positive reaction (and less than half were considered clinically relevant).
It seemed that when sensitization does occur, it's most commonly linked to topical medication (like corticosteroids) and not cosmetics. Allergic contact dermatitis also appears largely limited to individuals with underlying skin conditions.
Overall, propylene glycol is a well-studied ingredient that most people can tolerate without issue.
Learn more about Propylene GlycolTitanium 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 DioxideTriethanolamine (TEA) is an emulsifier and pH adjuster. It is created using ethylene oxide and ammonia. This gives Triethanolamine a nitrogen core and a similar scent to ammonia.
As an emulsifier, it prevents ingredients from separating and enhances texture by adding volume to a product.
PH adjusters are common in cosmetic products. The pH of a product can affect the effectiveness of other ingredients. A product with a high pH may also irritate the skin.
If you are looking for the tea leaf ingredient, click here.
Learn more about TriethanolamineWater. 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 WaterXanthan gum is used as a stabilizer and thickener within cosmetic products. It helps give products a sticky, thick feeling - preventing them from being too runny.
On the technical side of things, xanthan gum is a polysaccharide - a combination consisting of multiple sugar molecules bonded together.
Xanthan gum is a pretty common and great ingredient. It is a natural, non-toxic, non-irritating ingredient that is also commonly used in food products.
Learn more about Xanthan GumZinc 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