Dr. Diamond's Metacine HYDR/O Bioactive Hydrolipid Barrier Moisturizer

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.

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.

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.

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.

You might have heard of "niacin flush", or the reddening of skin that causes itchiness. Niacinamide has not been found to cause this.

In very rare cases, some individuals may not be able to tolerate niacinamide at all or experience an allergic reaction to it.

If you are experiencing flaking, irritation, and dryness with this ingredient, be sure to double check all your products as this ingredient can be found in all categories of skincare.

When incorporating niacinamide into your routine, look out for concentration amounts. Typically, 5% niacinamide provides benefits such as fading dark spots. However, if you have sensitive skin, it is better to begin with a smaller concentration.

When you apply niacinamide to your skin, your body converts it into nicotinamide adenine dinucleotide (NAD). NAD is an essential coenzyme that is already found in your cells as "fuel" and powers countless biological processes.

In your skin, NAD helps repair cell damage, produce new healthy cells, support collagen production, strengthen the skin barrier, and fight environmental stressors (like UV and pollution).

Our natural NAD levels start to decline with age, leading to slower skin repair, visible aging, and a weaker skin barrier. By providing your skin niacinamide, you're recharging your skin's NAD levels. This leads to stronger, healthier, and younger looking skin.

Another name for vitamin B3 is nicotinamide. This vitamin is water-soluble and our bodies don't store it. We obtain Vitamin B3 from either food or skincare. Meat, fish, wheat, yeast, and leafy greens contain vitamin B3.

The type of niacinamide used in skincare is synthetically created.

This ingredient has a low sensitization risk and testing shows it does not classify as a skin irritant or sensitizer.

FOS are usually produced from sugar beets and can also be found in foods like bananas, garlic, and onions.

On the safety side, the Cosmetic Ingredient Review Expert Panel has concluded this ingredient to be safe as used in current cosmetic practices + concentrations.

Typical use levels in a formula run about 1-5%.

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.

Read about common types of Hyaluronic Acid here:

A follow-up clinical trial found that a topical crosslinked HA serum applied after fillers, microneedling, or chemical peels was well-tolerated and enhanced skin quality at 14 / 28 days.

More recent research suggests that concentrations as low as 0.03% can act as a penetration enhancer for other skincare actives.

Regular hyaluronic acid carries a negative charge and so does the surface of your skin. This means the two repel each other and hyaluronic acid can be washed away easily. The positive charge here does the opposite: it makes the ingredient cling to your skin (also called "substantivity") so it keeps hydrating even in rinse-off products where it lays down a light, moisture-holding film.

The research backs this up too; a 2025 clinical study on a shower gel containing 0.1% positively charged hyaluronic acid increased skin hydration by 6.6% versus the baseline and 11.1% versus the placebo. This was measured 6 hours after 1 minute of contact and rinse, and on volunteers with very dry skin.

The same team's lab work showed it adhered to skin far better than unmodified hyaluronic acid (+107% vs. low molecular weight, +23% versus high molecular weight). They also found it increased two proteins tied to skin hydration, aquaporin-3 by 16% and filaggrin by 35%.

A separate 2024 study reached a similar conclusion and credited the hydrating benefits to its film-forming properties.

Both studies used the ingredient at 0.1% which also matches how much it usually shows up in products (at fractions of a percent).

One honesty note worth keeping in mind: the published research comes from the company that manufactures the ingredient so independent data would strengthen the picture. However, the results are consistent and the mechanism makes sense.

As a Hyaluronic Acid derivative, it has a well-tolerated profile and suits most skin types.

The only catch is that HA isn't a single thing; it actually comes in a wide range of molecular weights (~50 - 2,000+ kDA) and size matters.

Some clinical evidence links low molecular weight versions to improved wrinkle depth, elasticity, anti-inflammatory effects, and barrier repair.

This is why the best HA serums blend the two sizes together so you get the best of both worlds.

The majority of cosmetic HA is produced by bacterial fermentation, typically using Streptococcus or Bacillus strains. Typical use levels in skincare sit around 0.1-2%.

A clinical study using a 0.2% low-molecular weight HA gel showed improvement in facial seborrheic dermatitis with excellent tolerance.

These are some other common types of Hyaluronic Acid:

According to studies, low molecular-weight hyaluronic acid can:

One study from 2011 found ultra-low weight HA to show pro-inflammatory properties. Another study from 2022 found it to downregulate UV-B induced inflammation.

Hydrolysis is a process of changing a molecule using water or enzymes.

This ingredient is water-soluble.

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:

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.

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.

Studies show conditions like atopic dermatitis can worsen when ceramide NS levels are low.

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.

Your body uses linoleic acid to build ceramides and prostaglandins. Ceramides keep your skin's barrier hydrated and strong while prosaglandins help control inflammation and healing.

Needless to say, linoleic acid is crucial for having a strong skin barrier.

One study found applying linoleic acid rich sunflower oil to be more effective at repairing the skin barrier than olive oil.

This ingredient can also help treat acne by softening sebum to prevent clogged pores. Another study found using 2.5% linoleic acid gel for 4 weeks showed a 25% reduction in small comedones.

Studies show it can also help lighten hyperpigmentation or sun spots by disrupting the melanin production process. It also helps your skin shed melanin pigment from your skin caused by UV exposure.

Due to its role in the production of the fatty acid prostaglandin, linoleic acid can also help reduce inflammation and support wound healing.

Fun fact: Linoleic acid is an essential fatty acid. This means our bodies cannot create it on its own and we need to get it through foods such as nuts and vegetable oils.

Just know this ingredient is not always fungal-acne safe because it is a long-chain fatty acid (with 18 carbon atoms) that directly feeds the Malassezia yeast responsible for fungal acne.

ALA is a great skin hydrator because it has the ability to restore lipids in our stratum corneum, or outermost layer of our skin; it also helps prevent transepidermal water loss.

This ingredient also helps soothe irritated skin by downregulating inflammation.

Chia seed oil is one of the highest natural sources of ALA. Research shows topical chia seed oil significantly improves skin hydration, reduces itch, and strengthens the barrier in both healthy and extremely dry skin.

Additionally, in-vivo and in-vitro studies show ALA exhibits antioxidant properties, reduces UV-induced inflammation, and supports wound healing.

Early research showed a fatty-acid deficiency in animals leads to abnormal skin barrier function. It is believed a deficiency in linolenic acid may be linked to skin disorders like eczema.

Fun fact: This ingredient is considered an essential fatty acid for humans. This means our bodies cannot naturally produce it and we must get it from food. Some foods rich in linolenic acid include walnuts, fish oils, soy, and canola.

They work by fitting perfectly into your stratum corneum's lipid matrix since they're structurally similar to cholesterol. Here, they reinforce your skin's barrier.

One small in vivo human study showed topical soybean phytosterols sped up barrier recovery within three days on tape-stripped skin.

Broader research credits them with:

Formulation use typically sit under 5%.

Testing in soy-allergic subjects found no sensitization signals, but be sure to patch test if you are unsure or have existing allergies.

Aleurites Moluccanus Seed Oil can also help soothe the skin.

This nut has been used by many cultures for curing illnesses, such as headache and fever.

A 14 day human study found its moisturizing performance matched olive oil and tested as mild/low irritation on skin tissue.

It also showed gentle anti-inflammatory + antioxidant activity, plus the ability to stop Staphylococcus aureus (a bacteria tied to breakouts and eczema flares) from sticking to skin.

The concentration for this oil is flexible and can range from a few percent in serums up to 100% as a facial oil.

Since this ingredient is a triglyceride oil loaded with fatty acids that Malassezia can feed on, it may not be fungal acne safe.

Allergy-wise, the risk is low. Despite having the nicknames "Inca peanut" or "mountain peanut", this ingredient is not actually a peanut or tree nut. However, allergy to the seeds does exist so patch test if your skin is reactive.

Because they mirror the lipids naturally found in the deeper layers of your skin, topical phospholipids help reinforce the lipid matrix, reduce transepidermal water loss, and leave skin feeling conditioned.

They're also used to form liposomes, or tiny self-assembling vesible used to stabilize actives like vitamin c or retinol. This helps these ingredients integrate into the upper layers of skin more easily.

Phospholipids are compatible with everything and the CIR Expert Panel has concluded them to be safe at current use levels.

Some types of phospholipids include:

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

As an emollient, polyglyceryl-6 caprylate helps soften skin.

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.

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.

Interestingly, topically applied Palmitic Acid can be elongated into longer chain fatty acids and ceramides. A 2019 study found low levels of Palmitic Acid lead to slower development of cells, suggesting it plays a role in keeping your skin's renewal process on track.

The CIR (Cosmetic Ingredient Review) panel determined it safe as used in cosmetics at concentrations up to 13%. It is non-irritating and non-sensitizing in clinical studies.

The culprit behind fungal acne, the Malassezia yeast, feeds on fatty acids with carbon chain lengths between C11-C24. Palmitic Acid, at C16, falls right into that sweet spot.

In vitro studies have shown that Palmitic Acid is one of the fatty acids that induce rapid Malassezia growth in lab settings.

It's worth noting that what feeds yeast in a lab doesn't necessarily feed it on your face since formulation and your skin's chemistry play a bigger role.

Research shows:

A 1998 study did find that applying oleic acid at higher concentrations may cause irritation and disrupt the skin barrier. Modern formulations typically use low levels that is well-tolerated.

The culprit behind fungal acne, the Malassezia yeast, feeds on fatty acids with carbon chain lengths between C11-C24. Oleic Acid, at C18, falls right into that sweet spot.

In vitro studies have shown that Oleic Acid is one of the fatty acids that induce rapid Malassezia growth in lab settings.

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.

This ingredient is an emollient, emulsifier, and penetration enhancer. As an emollient, it helps soften and hydrate skin by trapping moisture within. As an emulsifier, it prevents oil and water ingredients from separating.

Hydrogenated Lecithin can form tiny spherical structures made of phospholipid bilayers called liposomes. These liposomes are able to capture compounds inside their structure and deliver them through the skin barrier.

Because phospholipids are a natural component of our cell membranes, this ingredient is inherently compatible with skin.

A 2021 study found lecithin-based surfactants were less harsh and more tolerable comared to Sodium Lauryl Sulfate (SLS).

This is why it works so well topically; PCA is a humectant that holds water in the stratum corneum and studies link higher skin PCA levels to better hydration + lower water loss. Interestingly, people show more PCA in summer and in normal vs dry skin.

Most of the benefits of this ingredient are related to hydration, softness, and barrier support.

A long-running review found that formulas with at least 2% PCA or its salts improved dry skin over both the short and long term. And the zinc salt is also used for its mild antimicrobial and astringent properties.

The salt forms are more common in cosmetics (like sodium PCA).

This ingredient is compatible with basically everything and pairs well with other humectants like glycerin or hyaluronic acid.

Usage-wise, it's typically used at low percentages (~0.2-2%).

The Cosmetic Ingredient Review Expert Panel has concluded PCA and its salts are safe as used and is non-irritating on skin even at high concentrations.

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.

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.

Beet root has many benefits when eaten. More research is needed on applying beetroot in skincare.

Beet Root is used to add pink/red color.

Fatty alcohols are usually derived from natural fats and oils and therefore do not have the same drying or irritating effect as solvent (ethanol) alcohols.

The FDA allows products labeled "alcohol-free" to have fatty alcohols.

This ingredient may not be fungal acne safe. It is a primary fatty alcohol with a chain length above 12 carbons. A study from 2019 show Malassezia can feed on fatty alcohols in this range, so it may trigger fungal acne in those prone to it.

Industry-reported use ranges from 8% in rinse-off products and 2% in leave-on formulations.

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.

On a cellular level, it disrupts the cell membranes of microbes by poking holes that make the cell leak. This shuts down the chemical reactions the microbe needs to make energy so it can no longer survive.

Another perk of this ingredient is that it stays functional across a wide pH range (3-10).

You'll often see it paired with boosters like Ethylhexylglycerin; one study showed that a 1:9 ratio of Ethylhexylglycerin to Phenoxyethanol damages bacterial membranes as effectively as doubling the Phenoxyethanol concentration on its own.

Typical use concentrations range from 0.3-1% depending on the formula, and this ingredient is capped at 1% int the EU.

Safety-wise, the fear mongering does not hold up to the evidence. The EU's Scientific Committee on Consumer Safety and FDA consider it safe as a preservative at up to 1%, including for children of all ages.

Adverse systemic effects only showed up in animal studies at exposures roughly 200x higher than what people get from cosmetics. And despite its very widespread use, this ingredient is a rare sensitizer and allergic reactions are uncommon.

Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).

As a humectant, it pulls water into the skin. But it's a pretty minor moisturizing ingredient compared to other humectants, like glycerin.

Interestingly, it can act as a mild penetration enhancer. One in vitro study on human skin found a 12% concentration upped the absorption of mometasone furoate (a medicinal ingredient used to treat inflammatory skin conditions) up to 7%.

This ingredient is typically used at levels of 0.1-10% depending on the role it's playing.

A patch test study on eczema patients didn't find a significant increase in irritation versus the control group, but the potential for irritation rises at higher concentrations.