Rationale #1 The Hydragel Versus Rationale #5 The Serum

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.

Citral is the molecule responsible for the fresh lemon scent in lemon, lime, and lemongrass. It is a fragrance ingredient that can be created from plant essential oils or synthetically.

Though Citral has documented antimicrobial activity against acne bacteria (which is where the marketing claims about it being good for acne-prone skin originate), real formulas use it at fragrance-level concentrations under 1% so there's likely no skin benefit.

Citric 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.

This ingredient is also known as bitter orange flower oil, or neroli flower oil. It imparts a floral, sweet, and citrusy scent.

It is rich in linalool, linalyl acetate, limonene, and nerolidol.

Citrus Aurantium Bergamia Fruit Oil is the oil from the bergamot orange and is primarily used as a fragrance. It has a "fresh" and "bright orange" scent.

The main aroma compounds found in this ingredient are limonene (~27-52%), linalool (~2-22%), and linalyl acetate (~27-40%). These are known EU fragrance allergens.

Citrus Aurantium Bergamia Leaf Oil is an oil.

Citrus Aurantium Dulcis Oil comes from the bitter orange, an orange native to Southeast Asia.

This orange is commonly used in cosmetics and food. It is a common ingredient for marmalade.

Citrus Grandis Peel Oil is an essential oil that is derived from the peel of a Grapefruit. It is composed largely of limonene, which is a fragrance that can cause irritation for sensitive skin.

Citrus Limon Peel Oil is created from the peels of the lemon. It is used to add a lemon-scent to products. Lemon peel oil also has antibacterial, antifungal, and antioxidant properties. However, it may also cause phototoxicity and sensitize skin.

Lemon peel oil contains limonene, a skin sensitizing ingredient. Another component is furanocoumarin, which induces phototoxicity in skin.

This ingredient is a copper salt known for its wound healing properties.

Our bodies use copper to help stabilize our skin's collagen and elastin. Its also an essential for superoxide dismutase, an enzyme with strong antioxidant properties.

This is an essential oil extracted from the leaves of the clove tree. It has a warm and spicy aroma.

Clove oils contain a high proportion of eugenol.

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).

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:

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 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.

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.

This essential oil is steam-distilled from the wood of the Juniperus tree. It's mainly a fragrance ingredient used to cover the scent of other ingredients. It has a warm, woody scent.

Be sure to patch test if you are sensitive to essential oils or fragrance.

We don't have a description for Leucine yet.

Limonene is a fragrance that adds scent and taste to a formulation.

It's found in the peel oil of citrus fruits and other plants such as lavender and eucalyptus. The scent of limonene is generally described as "sweet citrus".

Linalool is a fragrance and helps add scent to products. It's derived from common plants such as cinnamon, mint, citrus, and lavender.

Like Limonene, this ingredient oxidizes when exposed to air. Oxidized linalool can cause allergies and skin sensitivity.

Litsea Cubeba Fruit Oil is also known as May Chang essential oil. It is mostly used as a fragrance ingredient and has a bright, sweet, and lemony scent.

The main fragrance compounds in this ingredient are citral (~70-85%) and limonene.

Lysine is an essential amino acid (your body cannot make it on its own). It has skin conditioning properties and one of the key players in collagen synthesis.

When your body creates collagen, lysine is basically the glue that holds everything together. It helps collagen fibers lock into each other and stay strong, with vitamin C being its trusty sidekick. Without enough lysine, this glue gets flimsy and less firm, resulting in less bouncy skin.

We don't have a description for Magnesium Aspartate yet.

Pelargonium Graveolens Oil is the pressed oil of the Rose Geranium plant. It has perfuming and masking properties.

This ingredient contains citronellol and geraniol. These compounds may cause allergies and skin-sensitivity.

Pentylene glycol is typically used within a product to thicken it. It also adds a smooth, soft, and moisturizing feel to the product. It is naturally found in plants such as sugar beets.

The hydrophilic trait of Pentylene Glycol makes it a humectant. As a humectant, Pentylene Glycol helps draw moisture from the air to your skin. This can help keep your skin hydrated.

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.

Potassium Sorbate is a preservative used to prevent yeast and mold in products. It is commonly found in both cosmetic and food products.

This ingredient comes from potassium salt derived from sorbic acid. Sorbic acid is a natural antibiotic and effective against fungus.

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.

Santalum Spicatum Seed Oil is an oil.

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.

Sodium Benzoate is a preservative. It's used in both cosmetic and food products to inhibit the growth of mold and bacteria. It is typically produced synthetically.

Both the US FDA and EU Health Committee have approved the use of sodium benzoate. In the US, levels of 0.1% (of the total product) are allowed.

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.

Tyrosine is one of the amino acids used to create protein. It plays a role in melanin production.

A study from 2012 found tyrosine to show promising results in restoring skin volume.

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.

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.

Zinc gluconate has antibacterial and wound healing properties. It is particularly effective against fighting inflammatory acne.

This ingredient is the zinc salt of the PHA gluconic acid. PHAs are gentle cousins to AHAs.