What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Zinc Oxide 16.5%
Cosmetic ColorantAloe Barbadensis Leaf Juice
Skin ConditioningArachidyl Alcohol
EmollientArachidyl Glucoside
EmulsifyingBehenyl Alcohol
EmollientBisabolol
AntioxidantButyloctyl Salicylate
Skin ConditioningCamellia Sinensis Leaf Extract
AntimicrobialCaprylhydroxamic Acid
Caprylic/Capric Triglyceride
MaskingCapryloyl Glycerin/Sebacic Acid Copolymer
Skin ConditioningCaprylyl Glycol
EmollientCellulose Gum
Emulsion StabilisingCetearyl Alcohol
EmollientCitric Acid
BufferingCoco-Glucoside
CleansingCocos Nucifera Oil
MaskingCucumis Sativus Fruit Extract
EmollientEthyl Ferulate
AntioxidantGlycerin
HumectantIron Oxides
Lecithin
EmollientMethyl Dihydroabietate
Mica
Cosmetic ColorantMicrocrystalline Cellulose
AbsorbentNiacinamide
SmoothingOctyldodecyl Neopentanoate
EmollientOctyldodecyl Oleate
EmollientPolyhydroxystearic Acid
EmulsifyingPropanediol
SolventQuercetin
AntioxidantResveratrol
AntioxidantRubus Idaeus Seed Oil
EmollientSodium Gluconate
Skin ConditioningSodium Hyaluronate
HumectantSodium Stearoyl Glutamate
CleansingSqualane
EmollientTitanium Dioxide
Cosmetic ColorantTocopherol
AntioxidantWater
Skin ConditioningXanthan Gum
EmulsifyingZinc Oxide 16.5%, Aloe Barbadensis Leaf Juice, Arachidyl Alcohol, Arachidyl Glucoside, Behenyl Alcohol, Bisabolol, Butyloctyl Salicylate, Camellia Sinensis Leaf Extract, Caprylhydroxamic Acid, Caprylic/Capric Triglyceride, Capryloyl Glycerin/Sebacic Acid Copolymer, Caprylyl Glycol, Cellulose Gum, Cetearyl Alcohol, Citric Acid, Coco-Glucoside, Cocos Nucifera Oil, Cucumis Sativus Fruit Extract, Ethyl Ferulate, Glycerin, Iron Oxides, Lecithin, Methyl Dihydroabietate, Mica, Microcrystalline Cellulose, Niacinamide, Octyldodecyl Neopentanoate, Octyldodecyl Oleate, Polyhydroxystearic Acid, Propanediol, Quercetin, Resveratrol, Rubus Idaeus Seed Oil, Sodium Gluconate, Sodium Hyaluronate, Sodium Stearoyl Glutamate, Squalane, Titanium Dioxide, Tocopherol, Water, Xanthan Gum
Zinc Oxide 15.7%
Cosmetic ColorantAloe Barbadensis Leaf Juice
Skin ConditioningArachidyl Alcohol
EmollientArachidyl Glucoside
EmulsifyingBehenyl Alcohol
EmollientBisabolol
AntioxidantButyloctyl Salicylate
Skin ConditioningButyrospermum Parkii Butter
Skin ConditioningCaprylhydroxamic Acid
Capryloyl Glycerin/Sebacic Acid Copolymer
Skin ConditioningCaprylyl Glycol
EmollientCellulose Gum
Emulsion StabilisingCetearyl Alcohol
EmollientCetyl Alcohol
EmollientCitric Acid
BufferingCoco-Glucoside
CleansingCocos Nucifera Oil
MaskingDaucus Carota Sativa Seed Oil
EmollientDiheptyl Succinate
EmollientFerulic Acid
AntimicrobialGlycerin
HumectantHelianthus Annuus Extract
EmollientMethyl Dihydroabietate
Microcrystalline Cellulose
AbsorbentOryza Sativa Bran Extract
Skin ConditioningPersea Gratissima Oil
Skin ConditioningPolyglutamic Acid
Skin ConditioningRosmarinus Officinalis Leaf Extract
AntimicrobialRubus Idaeus Seed Oil
EmollientSodium Ascorbyl Phosphate
AntioxidantSodium Gluconate
Skin ConditioningSodium Hyaluronate
HumectantSodium Stearoyl Glutamate
CleansingSqualane
EmollientTheobroma Cacao Seed Butter
EmollientTocopherol
AntioxidantWater
Skin ConditioningZinc Oxide 15.7%, Aloe Barbadensis Leaf Juice, Arachidyl Alcohol, Arachidyl Glucoside, Behenyl Alcohol, Bisabolol, Butyloctyl Salicylate, Butyrospermum Parkii Butter, Caprylhydroxamic Acid, Capryloyl Glycerin/Sebacic Acid Copolymer, Caprylyl Glycol, Cellulose Gum, Cetearyl Alcohol, Cetyl Alcohol, Citric Acid, Coco-Glucoside, Cocos Nucifera Oil, Daucus Carota Sativa Seed Oil, Diheptyl Succinate, Ferulic Acid, Glycerin, Helianthus Annuus Extract, Methyl Dihydroabietate, Microcrystalline Cellulose, Oryza Sativa Bran Extract, Persea Gratissima Oil, Polyglutamic Acid, Rosmarinus Officinalis Leaf Extract, Rubus Idaeus Seed Oil, Sodium Ascorbyl Phosphate, Sodium Gluconate, Sodium Hyaluronate, Sodium Stearoyl Glutamate, Squalane, Theobroma Cacao Seed Butter, Tocopherol, 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.
Aloe Barbadensis Leaf Juice is the filtered, stabilized liquid pressed from the inner gel of the aloe vera leaf.
In cosmetics, it shows up as either soothing active or a water-replacement base. It is roughly 98-99% water and the last 1-2% is an interesting mix of polysaccharides, amino acids, vitamins, minerals, and enzymes.
The polysaccharides do most of the work: they bind water at the skin surface for a light, non-greasy hydration boost. And one of the polysaccharides, glycomannan, is linked to fibroblast stimulation + collagen synthesis. This is also why aloe has such a long track record in wound and burn healing.
This ingredient is also calming with anti-inflammatory and mild antimicrobial activity, making it a great pick for sensitive, irritated, or post-sun skin.
Realistic expectations matter though; the solid evidence is mostly limited to hydration, soothing, and wound support. Deeper claims about anti-aging or sun protection are not well backed, and science reviews note it does not prevent radiation-induced skin injury.
Because it plays well with almost everything, it's commonly used as a base alongside other actives like niacinamide or vitamin C.
Typical usage concentrations range from 0.5% (where hydration benefits already show up) all the way to 90%+ (where it replaces water as the main base).
The safety for this ingredient is well-establish as well. Overall, this is a great supporting ingredient for those who want a boost in hydration.
Learn more about Aloe Barbadensis Leaf JuiceArachidyl Alcohol is a fatty alcohol made from the the arachidic acid found in peanut oil.
Despite having "alcohol" in the name, it is not related to denatured alcohol or ethanol.
This ingredient is a multitasker:
Just be sure to patch this ingredient if you have a peanut allergy (though this ingredient is highly processed and the allergenic proteins are typically removed).
Learn more about Arachidyl AlcoholThis ingredient is a plant-based surfactant and emulsifier. It helps oil and water based ingredients mix evenly to improve formula stability without adding a "greasy" feel.
Behenyl Alcohol is a type of fatty alcohol (these are different from the drying, solvent alcohols).
Fatty Alcohols have hydrating properties and are most often used as an emollient or to thicken a product. They are usually derived from natural fats and oils; behenyl alcohol is derived from the fats of vegetable oils.
Emollients help keep your skin soft and hydrated by creating a film that traps moisture in.
In 2000, Behenyl Alcohol was approved by the US as medicine to reduce the duration of cold sores.
Learn more about Behenyl AlcoholBisabolol is a gentle skin conditioner, antioxidant, and soothing ingredient.
It's primary claim to fame is soothing and research shows topically applied bisabolol can quiet the chemical messengers that cause your skin to become inflamed, helping to sooth any irritation.
A clinical study found that applying 0.5% bisabolol daily for 8 weeks produced an average 9% decrease in skin pigmentation. Researchers found it can also suppress the process that leads to excess melanin production in skin.
In vitro studies found that bisabolol combined with propylene glycol significantly increased skin permeability by increasing lipid fluidity in the stratum corneum.
You'll likely see use concentrations quite low, usually 0.1-0.2%.
Overall, this is a well-tolerated ingredient that works well in formulas designed for sensitive, reactive, or post-procedure skin.
Learn more about BisabololButyloctyl Salicylate is a chemical UV filter structurally similar to octisalate. It is a photostabilizer, SPF booster, emollient and solvent. This ingredient helps evenly spread out ingredients.
According to a manufacturer, it is suitable for pairing with micro Titanium Dioxide, Zinc Oxide, and pigments.
Photostabilizers help stabilize UV-filters and prevents them from degrading quickly.
Learn more about Butyloctyl SalicylateCaprylhydroxamic Acid is a chelating agent that helps cosmetics stay fresh, stable, and consistent over time.
Chelating agents help prevent metal ions from binding to other ingredients. This helps prevent unwanted reactions and effects from using the product. It also helps prevent the growth of unwanted microbes in products that contain water.
Caprylhydroxamic Acid is often used with natural antimicrobial products as an alternative to preservatives.
Learn more about Caprylhydroxamic AcidWe don't have a description for Capryloyl Glycerin/Sebacic Acid Copolymer yet.
Caprylyl Glycol is a humectant, skin conditioner, emollient, and preservative booster derived from either caprylic acid or synthetically created.
Typical use levels vary from 0.3-1% as a preservative booster and go up to 2% to condition skin.
Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).
Learn more about Caprylyl GlycolCellulose Gum is a water-soluble polymer that comes from cellulose. It is used to change the texture of a product and to help stabilize emulsions.
As an emulsifier, cellulose gum specifically thicken the texture of water-based products.
This ingredient is considered hypoallergenic and non-toxic. Cellulose Gum can be found in cosmetics, food, and other household goods such as paper products.
Learn more about Cellulose GumCetearyl alcohol is a waxy mixture of two fatty alcohols: cetyl alcohol and stearyl alcohol. It is an emollient and emulsifier.
Despite having "alcohol" in its name, it has nothing to do with drying solvent alcohols; the FDA also allows "alcohol-free" products to contain fatty alcohols like this ingredient.
It plays several roles in a formula:
Typical use levels for this ingredient sit around 1-10% and the Cosmetic Ingredient Review Expert Panel has affirmed safety at concentrations up to 25% in leave-on products.
Multiple assessments have found it to be non-irritating and non-sensitizing to most people.
However, there have been some cases of allergic contact dermatitis in patients with chronically compromised skin barriers.
Cetearyl alcohol has a comedogenic rating of 2 and irritancy rating of 1. Both of these numbers come from the 1989 study that used rabbit ears; a "2" means mildly comedogenic and a "1" means low irritancy.
Here's the catch: rabbit skin is more sensitive than human skin and throws a lot of false positives. A 1996 reappraisal found that ingredients rated 1-2 in the rabbit ear tests are generally safe for humans.
Remember comedogenic ratings are unable to assess the entire formula of a product or how it will react on your skin. Just be sure to patch test if you are unsure about certain ingredients.
This ingredient is not fungal acne safe. Cetearyl alcohol is a fatty alcohol with chain lengths that fall within the range that Malassezia can metabolize.
A 2019 study has also observed Malassezia growth in the presence of this ingredient, confirming it to be not-fungal acne safe.
Learn more about Cetearyl AlcoholCitric Acid is an alpha hydroxy acid (AHA) naturally found in citrus fruits like oranges, lemons, and limes.
Like other AHAs, citric acid can exfoliate skin by breaking down the bonds that hold dead skin cells together. This helps reveal smoother and brighter skin underneath.
However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.
Due to this, citric acid is usually included in small amounts as a pH adjuster. This helps keep products slightly more acidic and compatible with skin's natural pH.
In skincare formulas, citric acid can:
While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.
Most citric acid used in skincare today is made by fermenting sugars (usually from molasses). This synthetic version is identical to the natural citrus form but easier to stabilize and use in formulations.
Read more about some other popular AHA's here:
Learn more about Citric AcidCoco-Glucoside is a surfactant, or a cleansing ingredient. It is made from glucose and coconut oil.
Surfactants help gather dirt, oil, and other pollutants from your skin to be rinsed away.
This ingredient is considered gentle and non-comedogenic. However, it may still be irritating for some.
Learn more about Coco-GlucosideThis 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 OilGlycerin (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 GlycerinWe don't have a description for Methyl Dihydroabietate yet.
Microcrystalline Cellulose is another name for refined wood pulp. It is used as an emulsifier and mattifying ingredient. As an emulsifier, it helps keep ingredients together.
Rubus Idaeus Seed Oil is created from the seeds of the raspberry fruit. Raspberries are native to northern Europe and Asia.
Raspberry seed oil is an emollient with antioxidant and anti-inflammatory properties. It is rich in fatty acids, tocopherols, flavonoids, Vitamin C, and Vitamin E.
As an emollient, raspberry seed oil helps hydrate your skin. Emollients prevent moisture from evaporating by creating a film on top.
Learn more about Rubus Idaeus Seed OilThis is the synthetic salt of gluconic acid, a form of PHA and mild exfoliant.
It is mainly used to stabilize oil and butter formulations from going bad. Sodium gluconate is a humectant, pH regulator, and chelating agent.
Chelating agents help neutralize unwanted metals from affecting the formulation.
Sodium gluconate is water-soluble.
Learn more about Sodium GluconateSodium Hyaluronate is the salt form of hyaluronic acid. It is a long sugar chain that is naturally found in your skin, joints, and connective tissue that maintains hydration and elasticity.
In skincare, it works as a humectant. It pulls water from the environment and deeper layers of skin and binds it to the surface.
Interestingly, the size of the molecule affects its behavior:
Some clinical evidence links low molecular weight versions to improved wrinkle depth, elasticity, anti-inflammatory effects, and barrier repair.
Many serums use a blend of both weights so you can get surface hydration plus longer-lasting and deeper effects.
You'll typically see concentrations between 0.1-2% for this ingredient.
Learn more about Sodium HyaluronateSodium Stearoyl Glutamate is an amino-acid based emulsifier. It is made by combining stearic acid with L-glutamic acid and neutralizing it to a sodium salt.
As an emulsifier, it works mainly as an oil-in-water one and helps keep the oil and water in your formulas blended. It also contributes to a smooth, non-greasy skin feel.
This ingredient is biodegradable and commonly available in natural/COSMOS-certified grades.
Learn more about Sodium Stearoyl GlutamateSqualane is the hydrogenated and shelf-stable form of squalene (a lipid that naturally occurs in human sebum).
It is an emollient and skin conditioning agent that is able to integrate seamlessly into the skin's lipid barrier without clogging pores.
This is due to how structurally similar it is to what your skin already produces.
Though it is mostly an emollient that helps soften and hydrate skin, it also has some humectant and occlusive action. Humectants help the skin retain moisture while occlusives seal it in, making squalane a triple-threat moisturizer.
Research shows it has antioxidant capabilities that help protect against stressors like UV exposure, specifically UVA induced oxidative stress. This study also found that it supports collagen biosynthesis in human dermal fibroblasts.
No clinical study has reported significant adverse effects and irritation reactions are very rare from this ingredient (even at 100% concentration).
Overall, it's a fantastic ingredient for hydration and is suitable for all skin types.
This depends on the source. Squalane can be derived from both plants and animals. Most squalane used in skincare comes from plants.
Please note: the source of squalane is only known if disclosed by the brand. We recommend reaching out to the brand if you have any questions about their squalane.
Read more about squalene with an "e".
Though squalane is often called an oil, it’s technically not one. It is a hydrocarbon, meaning it is only made of carbon and hydrogen. True oils are triglycerides and made of fatty acids and glycerol.
The term “oil-free” isn’t regulated so companies can define it however they want. Some exclude all oils, while others just avoid mineral oil or comedogenic oils.
Squalane has a comedogenic rating of 1 from the original 1972 study that tested raw ingredients under occlusion on rabbit ears. This system is not standardized or peer-reviewed, and using the raw ingredients is very different from how diluted cosmetic formulations are used on human skin.
A comedogenic rating of 1 means it is "unlikely to clog pores" according to the original rating system.
The overall formula of a product matters more than the individual ingredients on whether or not it will cause clogged pores.
Learn more about SqualaneTocopherol is a fat-soluble antioxidant known as Vitamin E.
You'll find this ingredient in the vast majority of skincare (for good reason). It works to neutralize free radicals, or unstable molecules generated by UV exposure, pollution, and other environmental stressors, before they can cause oxidative damage to your skin cells.
Topically applied tocopherol has been shown to protect against UV damage by ramping up the skin's own natural defense enzymes.
It also acts as a skin conditioning agent; some studies show that regular topical use can improve the skin's water-binding capacity over 2-4 weeks.
This ingredient is especially loved for being a team player. When combined with Vitamin C, the photoprotective effect of both ingredients roughly doubles and the combo also helps reduce UV-induced DNA damage.
This ingredient has some brightening potential but it's more of a prevention ingredient than spot-fader. Cell studies show it can slow down melanin production but it's worth noting that it's not the most powerful brightener out there.
In formulations, it also serves as a stabilizer that helps protect other oxidation-prone ingredients from degrading.
Concentrations usually range from 0.1-1% in most leave-on products.
Learn more about TocopherolWater. 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