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

Alanine

Masking, Skin Conditioning

Alanine is an amino acid and is already found in the human body. Our skin uses alanine to build collagen, elastin, and keratin.

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

Aspartic Acid

Masking, Skin Conditioning

Aspartic Acid is an amino acid that our bodies produce naturally. It is an antioxidant.

Our body uses Aspartic Acid to help build collagen and elastin. It also plays a role in hydrating skin.

Betaine

Humectant, Skin Conditioning

Betaine is a humectant. Like hyaluronic acid, it helps attract and retain moisture in the skin. It’s known for being gentle and for helping the skin maintain balanced hydration.

Betaine is mainly used to improve hydration and support calmer skin. It helps skin cells regulate water balance because it functions as an osmolyte.

Some studies suggest betaine may support making skin tone more even.

Fun fact: Betaine naturally exists in the skin and the body. In cosmetic products, it can be either plant-derived (most commonly from sugar beets) or synthetically produced for consistency and stability.

Betaine is also known as trimethylglycine.

Learn more about Betaine

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

Glutamic Acid

Humectant

Glutamic Acid is an amino acid that is found in all living organisms. Our bodies use this to help nerve cells in the brain communicate with other cells.

In cosmetics, glutamic acid is a famous humectant. It draws water from the air to your skin, keeping your skin hydrated (like hyaluronic acid).

An in-vitro study from 2024 found glutamic acid to play a role in inhibiting inflammation and thus a potential skin-soothing ingredient.

Other studies show it to be have potential wound healing, skin barrier repair, and hair growth properties.

Glutamic acid has poor solubility in water and other solvents.

Learn more about Glutamic Acid

Glycine

Buffering, Skin Conditioning

Glycine is the smallest amino acid and a key building block of collagen. It's part if 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.

A study from 2022 found that an amino acid complex featuring taurine, arginine, and glycine significantly reduced skin irritation, improved redness, and accelerated the skin repair process.

Histidine

Humectant, Skin Conditioning

Histidine is a semi-essential amino acid used by our bodies to create protein. It has humectant and skin conditioning properties.

Our bodies use histidine to create filaggrin - filaggrin is a structural protein that the skin uses in maintaining skin barrier.

One study found histidine and carnosine to be a dynamic duo for your skin:

Oral histidine has also been found to help with filaggrin-deficit skin disorders such as atopic dermatitis.

Why is it considered a semi-essential amino acid? This is because adults are able to create it but children must get it from their diet.

Learn more about Histidine

Isoleucine

Skin Conditioning

Isoleucine is an amino acid that helps reinforce our skin barrier. This amino acid plays a role in creating protein for the body.

Fun fact: Isoleucine is found in meat, fish, dairy, legumes, and nuts.

Panthenol

Skin Conditioning

Panthenol is a common ingredient that helps hydrate and soothe the skin. It is found naturally in our skin and hair.

There are two forms of panthenol: D and L.

D-panthenol is also known as dexpanthenol. Most cosmetics use dexpanthenol or a mixture of D and L-panthenol.

Panthenol is famous due to its ability to go deeper into the skin's layers. Using this ingredient has numerous pros (and no cons):

Like hyaluronic acid, panthenol is a humectant. Humectants are able to bind and hold large amounts of water to keep skin hydrated.

This ingredient works well for wound healing. It works by increasing tissue in the wound and helps close open wounds.

Once oxidized, panthenol converts to pantothenic acid. Panthothenic acid is found in all living cells.

This ingredient is also referred to as pro-vitamin B5.

Learn more about Panthenol

Phenylalanine

Masking, Skin Conditioning

Phenylalanine is an amino acid. It is a skin soothing and hydrating ingredient. Amino acids play a crucial role in wound healing and skin hydration.

This ingredient is also used to help even out skin tone due to its ability to disrupt the melanin production process.

Two structures of phenylalanine exist: L-phenylalanine and D-phenylalanine. L-phenylalanine is essential, this means our bodies cannot produce it naturally and we must get it from foods. Our bodies convert D-phenylalanine to neurotransmitters, and D-phenylalanine is found in our bodies naturally.

Some foods that contain L-phenylalanine include eggs, soybeans, beef, milk.

Learn more about Phenylalanine

Proline

Skin Conditioning

Proline is a non-essential amino acid, meaning your body can make it on its own. In skincare, it is a skin conditioning ingredient that keeps skin soft and hydrated.

It makes up about 23% of the collagen molecule (collagen is the protein responsible for keeping your skin firm) and is involved in your skin's natural hyaluronic acid production. When applied topically, proline can penetrate the skin fairly well due to its small molecular size.

Reviews of this ingredient have found it to be neither a dermal irritant nor a sensitizer.

Fun fact: Proline can be found in protein-rich foods like meat, fish, eggs, and dairy.

Learn more about Proline

Propanediol

Solvent

Propanediol is an all-star ingredient. It softens, hydrates, and smooths the skin.

It’s often used to:

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.

Learn more about Propanediol

Serine

Masking, Skin Conditioning

Serine is a non-essential amino acid (your body makes it on its own!). It is a major player in 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.

Serine is one of your NMF's most abundant components that works as a skin-identical humectant. Its hydroxyl group grabs onto water molecules to boost hydration without any heaviness or occlusion.

Research on a hydrogel with serine confirmed this serine got delivered to your stratum corneum and demonstrated enhanced skin moisturization.

Interestingly serine also helps your skin produce filaggrin, a protein that keeps your skin barrier strong and used to create collagen.

Learn more about Serine

Threonine

Threonine is an amino-acid. It helps hydrate the skin and has antioxidant benefits.

Our skin uses threonine for creating collagen and elastin. Humans are not able to create threonine and must get it through eating foods such as fish, lentils, poultry, sesame seeds, and more.

Valine

Masking, Skin Conditioning

Valine is an essential amino acid. It is used by our bodies for tissue repair and muscle growth.

An essential amino acid is one in which our bodies cannot naturally produce so we must get them through diet. Foods such as eggs, dairy, red meat, and fish contain valine.

This ingredient can either be derived from an animal product or be synthetically created.

Learn more about Valine

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