What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Water
Skin ConditioningZinc Oxide
Cosmetic ColorantDibutyl Adipate
EmollientTitanium Dioxide
Cosmetic ColorantIsononyl Isononanoate
EmollientCetyl Alcohol
EmollientNiacinamide
SmoothingCetearyl Alcohol
EmollientAvena Sativa Kernel Flour
AbrasiveC12-15 Alkyl Benzoate
AntimicrobialGlycerin
HumectantJojoba Esters
EmollientGlyceryl Stearate
EmollientAllantoin
Skin ConditioningCaprylic/Capric Triglyceride
MaskingAluminum Hydroxide
EmollientTriethoxycaprylylsilane
Polyhydroxystearic Acid
EmulsifyingStearic Acid
CleansingHelianthus Annuus Seed Wax
Skin ConditioningSodium Stearoyl Glutamate
CleansingBisabolol
AntioxidantTocopheryl Acetate
AntioxidantCitric Acid
BufferingSodium Hyaluronate
HumectantLavandula Angustifolia Oil
MaskingCitrus Medica Peel Oil
Sodium Benzoate
MaskingPotassium Sorbate
PreservativeXanthan Gum
EmulsifyingCeramide NP
Skin ConditioningCeramide AP
Skin ConditioningPhytosphingosine
Skin ConditioningCholesterol
EmollientSodium Lauroyl Lactylate
EmulsifyingCeramide EOP
Skin ConditioningPolyglycerin-3
HumectantEthylhexylglycerin
Skin ConditioningCarbomer
Emulsion StabilisingWater, Zinc Oxide, Dibutyl Adipate, Titanium Dioxide, Isononyl Isononanoate, Cetyl Alcohol, Niacinamide, Cetearyl Alcohol, Avena Sativa Kernel Flour, C12-15 Alkyl Benzoate, Glycerin, Jojoba Esters, Glyceryl Stearate, Allantoin, Caprylic/Capric Triglyceride, Aluminum Hydroxide, Triethoxycaprylylsilane, Polyhydroxystearic Acid, Stearic Acid, Helianthus Annuus Seed Wax, Sodium Stearoyl Glutamate, Bisabolol, Tocopheryl Acetate, Citric Acid, Sodium Hyaluronate, Lavandula Angustifolia Oil, Citrus Medica Peel Oil, Sodium Benzoate, Potassium Sorbate, Xanthan Gum, Ceramide NP, Ceramide AP, Phytosphingosine, Cholesterol, Sodium Lauroyl Lactylate, Ceramide EOP, Polyglycerin-3, Ethylhexylglycerin, Carbomer
Zinc Oxide
Cosmetic ColorantAllantoin
Skin ConditioningBisabolol
AntioxidantButyloctyl Salicylate
Skin ConditioningC12-15 Alkyl Benzoate
AntimicrobialCaprylic/Capric Triglyceride
MaskingCapryloyl Glycerin/Sebacic Acid Copolymer
Skin ConditioningCarbomer
Emulsion StabilisingCeramide AP
Skin ConditioningCeramide EOP
Skin ConditioningCeramide NP
Skin ConditioningCetearyl Alcohol
EmollientCetyl Palmitate
EmollientCholesterol
EmollientCitric Acid
BufferingDiisopropyl Sebacate
EmollientEthylhexyl Methoxycrylene
Skin ConditioningEthylhexylglycerin
Skin ConditioningGarcinia Indica Seed Butter
Skin ConditioningGlycerin
HumectantHydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer
Emulsion StabilisingIsodecyl Neopentanoate
EmollientLauryl Lactate
EmollientPhenoxyethanol
PreservativePhytosphingosine
Skin ConditioningPolyhydroxystearic Acid
EmulsifyingPolysorbate 60
EmulsifyingPotassium Cetyl Phosphate
EmulsifyingSodium Hyaluronate
HumectantSodium Hydroxide
BufferingSodium Lauroyl Lactylate
EmulsifyingSorbitan Isostearate
EmulsifyingSorbitan Olivate
EmulsifyingSorbitan Palmitate
EmulsifyingSqualane
EmollientTetrasodium Glutamate Diacetate
Tocopherol
AntioxidantTriethoxycaprylylsilane
Water
Skin ConditioningXanthan Gum
EmulsifyingCI 77491
Cosmetic ColorantCI 77492
Cosmetic ColorantCI 77499
Cosmetic ColorantZinc Oxide, Allantoin, Bisabolol, Butyloctyl Salicylate, C12-15 Alkyl Benzoate, Caprylic/Capric Triglyceride, Capryloyl Glycerin/Sebacic Acid Copolymer, Carbomer, Ceramide AP, Ceramide EOP, Ceramide NP, Cetearyl Alcohol, Cetyl Palmitate, Cholesterol, Citric Acid, Diisopropyl Sebacate, Ethylhexyl Methoxycrylene, Ethylhexylglycerin, Garcinia Indica Seed Butter, Glycerin, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Isodecyl Neopentanoate, Lauryl Lactate, Phenoxyethanol, Phytosphingosine, Polyhydroxystearic Acid, Polysorbate 60, Potassium Cetyl Phosphate, Sodium Hyaluronate, Sodium Hydroxide, Sodium Lauroyl Lactylate, Sorbitan Isostearate, Sorbitan Olivate, Sorbitan Palmitate, Squalane, Tetrasodium Glutamate Diacetate, Tocopherol, Triethoxycaprylylsilane, Water, Xanthan Gum, CI 77491, CI 77492, CI 77499
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 AllantoinBisabolol 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 BisabololC12-15 Alkyl Benzoate is a lightweight emollient made by combinig benzoic acid with fatty alcohols that are 12-15 carbons long.
In cosmetics, it plays several roles:
The Cosmetic Review Expert Panel has concluded the alkyl benzoate group to be safe as used in cosmetics; it wasn't found to be a skin irritant and unlikely to be absorbed due to its low water solubility.
This report recorded almost 1000 reported uses with concentrations up to 59% in leave-on products but your cosmetics will typically use 0.5-15% depending on the product.
It's often called a "SPF booster": this is because it keeps UV filters properly dissolved and evenly distributed to support a sunscreen's performance. It doesn't actually raise SPF on its own.
Overall, this ingredient is well tolerated.
This ingredient is fungal acne safe because it is an ester of benzoic acid.
Think of this ingredient as two parts stuck together: an oily part and an acid part. Malassezia only gets a meal when it can snip off a fatty acid to eat. With C12-15 Alkyl Benzoate, the acid part is benzoic acid, which isn't a fatty acid and which the yeast can't use as food.
Benzoic acid is actually used as a preservative to stop yeast from growing.
The oily part is a blend of C12-15 fatty alcohols but fatty alcohols in this size range can support only a little Malassezia growth (mostly for one species of Malassezia as well).
In the ingredient, those alcohols stay locked inside the molecule. The yeast can only reach them by snipping the benzoate bond, and that type of bond is harder for it to cut than a normal fatty bond.
So not much gets released. And whatever does get snipped comes packaged with benzoic acid, which discourages yeast growth.
Learn more about C12-15 Alkyl BenzoateCaprylic/Capric Triglyceride (aka MCT Oil) is a lightweight emollient, solvent, and texture enhancer. It is considered a skin-softener by helping to prevent moisture loss.
Though it behaves like an oil, it is not technically one due to its chemical composition. One perk of this ingredient is that it is very stable, resistant to oxidation, and unlikely to go rancid.
In practice, that translates to a long shelf life and a consistently elegant skin feel.
While there is an assumption Caprylic Triglyceride can clog pores due to it being derived from coconut oil, there is no research supporting this. Just patch test if you have concerns.
Fractionated coconut oil and MCT Oil are both listed as Caprylic/Capric Triglyceride according to INCI. This is because INCI names are based on the ingredient’s final chemical composition and not its marketing name or source.
This ingredient is treated as the gold standard fungal acne safe oil. Even though it is coconut derived, the problematic lauric acid is stripped out.
This leaves just caprylic (C8) and capric (C10) acid. These chain lengths actually trend antifungal; a 2020 study found caprylic acid was enough to disrupt Malassezia furfur cell membrane, with a caprylic acid derivative damaging membrane structures at concentrations as low as 0.2%.
Learn more about Caprylic/Capric TriglycerideCarbomer is a synthetic thickening and gelling agent. It's basically the ingredient that gives a lot of serums, gels, creams, and sunscreens their smooth, non-sticky texture.
Although legally permitted at very high levels, carbomers are normally used at concentrations below 1%.
It also needs to be neutralized to actually thicken, and because it is a large molecule, it doesn't really penetrate the skin barrier.
Allergy-wise, the risk is very low. Clinical studies show carbomers have low potential for skin irritation/sensitization even at concentrations up to 100%.
A 2024 UK study patch-tested 1,302 patients and found true allergy to the parent group of carbomer to be rare with no confirmed relevant reactions.
Learn more about CarbomerCeramide AP is is a skin-identical lipid that mimics what your skin already makes naturally. Ceramides help maintain epidermal integrity and barrier function.
You'll often see this ingredient paired with other ceramides (like ceramide NP), cholesterol, or fatty acids because this combination best mimics the natural lipid mix your skin already has.
The skin's ability to produce ceramides gets disrupted in skin conditions like eczema. This in turn weakens the skin barrier and applying ceramides topically has been shown to replenish what's been lost to restore barrier function.
Most of the studies with Ceramide AP test it as part of a multi-ceramide complex; studies reinforce ceramide AP's role in rebalancing ceramides in skin and improving skin hydration.
Learn more about Ceramide APCeramide EOP is formally known as Ceramide 1.
It is naturally found in skin and part of the intercellular "mortar" holding everything together in your outermost layer.
EOP stands for a linked Ester fatty acid, a linked Omega hydroxy fatty acid, and the Phytosphingosine base.
What makes Ceramide EOP special is its ultra-long fatty acid chain; this unique structure allows it to bridge the lipid layers in your skin barrier to prevent water loss (something no other ceramide can do).
Low levels of Ceramide EOP have been found in people with eczema and psoriasis.
Using it together with other ceramides, cholesterol, and linoleic acid have been shown to meaningfully improve hydration and reduce water loss.
In one clinical study, a regimen using Ceramide EOP, NP, and AP led to significant symptom improvements in patients with eczema, psoriasis, and dry skin in just 4 weeks.
You'll usually see concentrations between 0.1-0.5% in formulations. Overall, this is a well-tolerated and safe ingredient for cosmetic use.
Learn more about Ceramide EOPCeramide NP (formerly known as Ceramide 3) is one of the skin's naturally occurring lipids.
Since ceramides are the major lipid components of the skin, they are crucial for maintaining skin barrier and hydration. Ceramide NP most closely mirrors the dominant kind in human skin amongst ceramide subtypes.
This ceramide works by slotting into gaps within the stratum corneum's lipid matrix to limit trans-epidermal water loss (TEWL) and shield the skin against external irritants.
A study with 312 patients found that using a ceramide-containing routine for 4 weeks reduced the severity of atopic dermatitis by over 61%.
Another clinical study in subjects aged 60 and older found that a ceramide body wash and moisturizer improved skin dryness and itchy skin in 15 days.
Overall, ceramides are considered non-irritating and safety tests have found little to no observable adverse effects from using this ingredient.
Ceramide NP is usually sourced from plants (like soybean or rice bran), or produced synthetically.
Learn more about Ceramide NPCetearyl 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 AlcoholCholesterol is a lipid that is naturally found in human skin and is one of the three key components of your skin barrier. In skincare, it is an emollient and barrier-repairing ingredient.
It works by fitting directly into the lipid layers of skin to help restore structure and reduce transepidermal water loss (TEWL).
This is a great ingredient for dry, compromised, or aging skin; our skin starts to produce less cholesterol with age.
Research shows cholesterol works best in combination with ceramides and fatty acids, the other two major components in your skin barrier.
Cholesterol is also a well-establish penetration enhancer and can help other actives absorb more effectively.
Cosmetic-grade cholesterol is usually derived from lanolin but plant and synthetic options also exist. We recommend reaching out to the brand if you have questions about their source of cholesterol.
Learn more about CholesterolCitric 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 AcidEthylhexylglycerin is created from glycerin. It is a multitasker ingredient that:
The CIR Expert Panel found minimal skin absorption or sensitization of any kind in a safety assessment. Though this ingredient is considered well-tolerated, a small number of cases of allergic dermatitis have been published since 2002. Just be sure to patch test if you are unsure.
Industry-reported use ranges from 8% in rinse-off products and 2% in leave-on formulations.
Learn more about EthylhexylglycerinGlycerin (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 GlycerinPhytosphingosine is a phospholipid naturally found in our skin as a building block for ceramides.. It helps moisturize, soothe, and protect skin.
Phytosphingosine contributes to your skin's natural moisturizing factor (NMF). The NMF is responsible for hydration, a strong barrier, and plasticity. Our NMF decreases with age. Increasing NMF leads to more healthy and hydrated skin.
Studies show products formulated with NMF ingredients help strengthen our skin's barrier. Having a healthy skin barrier reduces irritation and increases hydration. Our skin barrier is responsible for having plump and firm skin. It also helps protect our skin against infection, allergies, and inflammation.
Fun fact: Phytosphingosine is abundant in plants and fungi.
More ingredients that help boost collagen in skin:
Learn more about PhytosphingosinePolyhydroxystearic Acid is a vegetable-derived soft wax made from castor oil. It's an emulsion stabilizer, thickener, and film former.
You'll likely see it in sunscreens because it helps disperse pigments and UV-reflecting minerals like titanium dioxide and zinc oxide evenly.
Depending on the concentration, it can drastically change the texture of a product from pasty solid (like lipstick) to sprayable liquid.
The CIR Expert Panel for Cosmetic Ingredient Safety has concluded this ingredient to be safe in cosmetics. The highest reported use concentration is 14.2% in lipsticks.
Learn more about Polyhydroxystearic AcidSodium 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 Lauroyl Lactylate (SLL) is a mild, plant-derived surfactant made by combining lauric acid with lactic acid.
It has two main jobs in a formula:
A perk of this ingredient is that it leaves skin feeling soft and silky after rinsing. This is why you'll even see it in baby washes.
Another perk?
The lauric acid backbone gives it mild antimicrobial activity and lauric acid itself has been shown to suppress acne-causing bacteria in lab studies.
In 2023, scientists took a close look at how SLL behaves and found it can break apart the fatty outer layers of cells. This is basically why it cleans well and can fight off certain microbes.
The Cosmetic Ingredient Review (CIR) Expert Panel has reviewed it and concluded it's safe as used.
A 2017 survey showed concentrations up to 10% are used in rinse-off cleansers and roughly 0.5-5% being typical in skincare.
Animal and reconstructed-skin testing found it to be non-irritating at 10%, and it's well tolerated even on sensitive skin. The only caveat is to patch test if you have a lactic acid allergy.
As a lactylate salt used at low co-emulsifier concentrations, this ingredient is less likely to break down and release free lauric acid on skin. This ingredient is fungal acne safe.
Learn more about Sodium Lauroyl LactylateTriethoxycaprylylsilane is a silicon-based surface modifier that makes sunscreens feel silky and makeup stay put.
Its main job is to coat mineral particles like titanium dioxide, zinc oxide, and color pigments in a thin, oily layer so they spread smoothly, don't clump, and stick to skin better.
This ingredient is typically used at low levels (up to 2.5% in eyeshadow and 1% in lipstick).
Learn more about TriethoxycaprylylsilaneWater. 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