Humectant, drawing moisture into the skin
Emollient, helping to soften skin
Solvent, dispersing and stabilizing formulas
Preservative booster, enhancing the antimicrobial activity of other preservatives

Arginine

Masking, Skin Conditioning

Arginine is a semi-essential amino acid. This just means our bodies can product a bit on its own, but sometimes needs a little boost from food sources.

It is a part of your skin's natural moisturizing factor (NMF), or the water-loving molecules in your outermost layer of skin (stratum corneum) that keeps everything hydrated and happy.

Here's an interesting thing about Arginine: your skin converts it into urea through the Krebs-Henseleit urea cycle. Urea is one of the most effective humectants your skin naturally produces.

A clinical study showed applying 2.5% arginine hydrochloride to atopic dermatitis skin showed significant urea levels in the stratum corneum and improved moisture in just four weeks.

Arginine is also a precursor to nitric oxide; nitric oxide improves microcirculation and supports wound healing and collagen synthesis.

One study found that an amino acid complex containing Arginine reduced skin irritation, improved hydration, and accelerated skin repair in clinical / in-vivo studies.

Arginine itself is an amino acid and not a fatty acid, oil, or ester. On its own, it's not a direct food source for Malassezia, or the yeast that causes fungal acne.

Learn more about Arginine

Butylene Glycol

Humectant, Masking, Skin Conditioning

Butylene Glycol (or BG) is used within cosmetic products for a few different reasons:

Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.

Though this ingredient works well with most skin types, some people with sensitive skin may experience a reaction such as allergic rashes, closed comedones, or itchiness.

Learn more about Butylene Glycol

Caprylyl Glycol

Emollient, Humectant, Skin Conditioning

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 or alcohol, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).

Learn more about Caprylyl Glycol

Citrullus Lanatus Fruit Extract

Skin Conditioning

Citrullus Lanatus Fruit Extract comes from the watermelon. Watermelon has antioxidant and anti-inflammatory properties.

Watermelons are rich in antioxidants such as Vitamin A, Vitamin C and lycopene. It also contains sugars and amino acids, such as arginine and glutathione.

Lycopene is a potent antioxidant. Besides helping to protect your skin against free-radical molecules, it also helps soothe the skin. Lycopene gives watermelon the distinct red color.

Learn more about Citrullus Lanatus Fruit Extract

Cysteine

Antioxidant, Masking

Cysteine is an amino acid found in our bodies. It becomes an antioxidant when converted into gluthatione.

Once it becomes gluthatione, it prevents oxidative damage to parts of our cell. Gluthatione has also been shown to protect our skin from UV-B induced damage.

Ethylhexylglycerin

Skin Conditioning

Ethylhexylglycerin 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 Ethylhexylglycerin

Glycerin

Humectant, Skin Conditioning, Skin Protecting

Glycerin (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 Glycerin

Hyaluronic Acid

Humectant, Moisturising, Skin Conditioning

Hyaluronic acid (HA) is a glycosaminoglycan (basically a long sugar chain) that your skin already makes on its own. In your skin, HA lives in the extracellular matrix and acts as the body's moisture reservoir.

Topically, HA is a humectant that binds water and helps skin look more plump, smooth, and hydrated.

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:

Learn more about Hyaluronic Acid

Hydrolyzed Hyaluronic Acid

Humectant, Skin Conditioning

Hydrolyzed Hyaluronic Acid is hyaluronic acid (HA) that is broken down into lower molecular weight fragments.

It's a humectant that pulls and holds water in the skin to help with hydration, plumpness, and reduce transepidermal water loss.

Because hydrolyzed hyaluronic acid is smaller in size, it can slip past your outermost layer of skin more easily than full-sized HA.

Most formulations will combine all sizes to get the best of both worlds.

Typical usage levels range from 0.01-1%. Any percentage higher than 2% might become goopy and tacky.

Learn more about Hydrolyzed Hyaluronic Acid

Methionine

Skin Conditioning

Methionine is an essential amino acid. It is a conditioning agent and commonly found in both skin and hair products.

This amino acid is a precursor to glutathione, a powerful antioxidant.

Fun fact: Methionine can be found in meat, fish, and dairy. It cannot be naturally produce and requires dietary intake.

Learn more about Methionine

Sodium Hyaluronate

Humectant, Skin Conditioning

Sodium 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 Hyaluronate

Sodium Hyaluronate Crosspolymer

Humectant, Skin Conditioning

Sodium Hyaluronate Crosspolymer is a crosslinked version of sodium hyaluronate. This just means it's linked into a 3D mesh network that lets it be more stable and sit on skin as a cohesive, gel-like film rather than sinking into skin.

A 2016 human skin study found crosslinked HA increased epidermal water content by 7.6% over the control group and reduced transepidermal water loss by 27.8%.

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.

Learn more about Sodium Hyaluronate Crosspolymer

Sodium PCA

Humectant, Skin Conditioning

Sodium PCA is the sodium salt of pyroglutamic acid. It is naturally occurring in our skin's natural moisturizing factors where it works to maintain hydration.

The PCA stands for pyrrolidone carboxylic acid, a natural amino acid derivative.

This ingredient has skin conditioning, anti-inflammatory, and humectant properties. Humectants help hydrate your skin by drawing moisture from the air. This helps keep your skin moisturized.

Learn more about Sodium PCA

Sodium Polyacryloyldimethyl Taurate

Emulsion Stabilising

Sodium Polyacryloyldimethyl Taurate is a polymer and used to help stabilize other ingredients.

Emulsion stabilizers hold ingredients together, helping to create an even texture throughout the product.

Sodium Polyacryloyldimethyl Taurate can also be used to thicken the texture.

Learn more about Sodium Polyacryloyldimethyl Taurate

Tremella Fuciformis Extract

Humectant, Skin Conditioning

Tremella Fuciformis Extract comes from the tremella fuciformis mushroom, also known as snow mushroom or white jelly mushroom.

The snow mushroom has moisturizing and antioxidant properties.

Snow mushroom is rich in polysaccharides, giving it moisturizing benefits. As a humectant, snow mushroom helps draw moisture from the air to the skin. Polysaccharides are able to mimic our skin's natural carbohydrates to help the skin retain water.

Snow mushroom has been shown to help with anti-aging due to its antioxidants. It increases the presence of superoxide dismutase in our brain and liver. Superoxide is a by-product of oxygen metabolism. It left unregulated, superoxide causes cell damage. Thus, superoxide dismutase acts as an antioxidant to protect our living cells.

Another study from 2016 showed snow mushroom extract blocks the skin from creating melanin when exposed to UVB. Thus, it may help protect against the signs of aging from sun exposure. However, more studies are needed to confirm this. Another study from 2021 found snow mushroom to protect against UVA damage as well.

This white mushroom is native to Asian countries such as China, Korea, Japan, and Thailand. It is a common ingredient in traditional Chinese cuisine and medicine.

Learn more about Tremella Fuciformis Extract

Water

Skin Conditioning, Solvent

Water. 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 Water