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

Adenosine

Skin Conditioning

Adenosine is a purine nucleoside that your body already makes in every cell. In skincare, it acts mainly as a skin conditioning and anti-aging agent.

The way it works is fairly well mapped out:

Your skin has cells called fibroblasts that build collagen (the stuff that keeps skin firm and smooth). Adenosine basically flips a switch on these cells that tells them to get to work making more collagen and other proteins. These cells slow down on their own as skin ages, so Adenosine helps give them a little nudge to keep going.

The clinical backing is pretty solid too.

A blind, randomized, placebo-controlled trial of 126 women aged 45-65 tested a 0.1% cream twice daily and found real improvements in crow's feet and frown lines using a precise 3D skin-mapping technique; these changes showed up by week 3 and held at 2 months.

A later study using Adenosine-loaded dissolving microneedle patches reported gains in wrinkle depth, dermal density, elasticity, and hydration.

On concentrations, South Korea's Ministry of Food and Drug Safety has set 0.04% as the approved functional anti-wrinkle level. You'll typically see this ingredient used somewhere in the 0.04-0.1% range since it works at low doses.

This ingredient has been found safe for cosmetics with the data showing no irritation or sensitization.

Overall, this is a great ingredient for any anti-aging routine and has no photosensitizing effect, so it suits both AM and PM use.

Learn more about Adenosine

Behenyl Alcohol

Emollient, Emulsion Stabilising

Behenyl Alcohol is a type of fatty alcohol (these are different from the drying, solvent alcohols).

Fatty Alcohols have hydrating properties and are most often used as an emollient or to thicken a product. They are usually derived from natural fats and oils; behenyl alcohol is derived from the fats of vegetable oils.

Emollients help keep your skin soft and hydrated by creating a film that traps moisture in.

In 2000, Behenyl Alcohol was approved by the US as medicine to reduce the duration of cold sores.

Learn more about Behenyl Alcohol

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

Cholesterol

Emollient, Emulsifying, Skin Conditioning

Cholesterol 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 Cholesterol

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

Glucose

Humectant

Glucose is a simple sugar (a monosaccharide). In skincare, it is mostly a humectant and skin conditioning agent.

Mechanistically, it has multiple hydroxyl groups that hydrogen-bond to water. This pulls moisture into the upper layers of skin to keep the surface soft and hydrated.

It's worth knowing sugars are already a natural component of the skin's NMF (natural moisturizing factor) so it's a molecule that your stratum corneum is well-acquainted with.

Just so you know, glucose is hydrophilic (water-loving) and the stratum corneum is a strong barrier to hydrophilic compounds. This just means penetration is slow and most of the action is happening on the surface.

Gram-to-gram, glucose is not as efficient as a humectant as glycerin. This is why you'll likely see glycose paired with stronger humectants for a bigger hydration payoff.

In skincare, glucose is typically derived from corn or other starch sources.

Learn more about Glucose

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

Hydrogenated Lecithin

Emulsifying, Skin Conditioning

Hydrogenated Lecithin is a more stable version of lecithin.

It's made by taking lecithin (a phospholipid commonly found in soybeans and egg yolks) and hydrogenating it. This just means the unsaturated fatty acids are turned into saturated ones so they don't go bad as easily.

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).

Learn more about Hydrogenated Lecithin

Hydroxyacetophenone

Antioxidant

Hydroxyacetophenone is a small phenolic molecule that earns its place in a formulas as an antioxidant and preservative booster.

As a phenol, it is able to neutralize free radicals to protect both the product and the skin from oxidative stress.

Though it can't kill microbes on its own, it works as a good supporting agent when combined with other preservatives like Phenoxyethanol or 1,2-Hexanediol.

This ingredient naturally occurs as piceol in Norwegian spruce needles (~0.4-1.1% dry weight and in cloudberries). Though the cosmetic-grade material is synthesized for purity and consistency.

You'll usually see it used at low levels and suppliers recommend up to 1% added to a water phase.

Safety testing was done at concentrations like 0.05% in SPF products and 0.5% in a Human Repeated Insult Patch Test. The safety evidence is assuring; this ingredient is safe for cosmetics in current use and also holds safety status as a food flavoring as well.

An honest caveat: the "soothing" and "anti-inflammatory" claims come mostly from supplier marketing rather than published clinical trials. The Cosmetic Ingredient Review's own literature search found no useful efficacy studies on this ingredient.

So the antioxidant and preservative-boosting roles are the well supported ones while the calming benefit is plausible but thinly evidenced.

Overall, this is a well-tolerated, low-irritation multitasker that quietly helps a formula stay fresh and stable.

Learn more about Hydroxyacetophenone

Niacinamide

Smoothing

Niacinamide is a multitasking form of vitamin B3 that strengthens the skin barrier, reduces pores and dark spots, regulates oil, and improves signs of aging.

And the best part? It's gentle and well-tolerated by most skin types, including sensitive and reactive skin.

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.

Learn more about Niacinamide

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

Pentylene Glycol

Skin Conditioning, Solvent

Pentylene Glycol (1,2-pentanediol) is a multitasking little diol with three main roles in a formula:

Research on alkanediols (the family pentylene glycol belongs to) show they work by disrupting microbial cell membranes. This disruption helps the primary preservative system in a product work more effectively at lower doses.

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%.

Learn more about Pentylene Glycol

Polysorbate 20

Emulsifying, Surfactant

Polysorbate 20 is a gentle, water-soluble emulsifier and mild surfactant. It stops oil and water from separating to keep your formulas blended and stable.

It also acts as a mild penetration enhancer by helping active ingredients absorb slightly better.

The common safety discussion around this ingredient involves a manufacturing byproduct called 1,4-dioxane.

Trace amounts can form during production but the EU's Scientific Committee on Consumer Safety has concluded that levels at/below 10 ppm in finished products are safe (commercial products consistently fall within acceptable margins).

True allergic reactions are uncommon and the CIR Expert Panel has confirmed this ingredient to be safe as used in cosmetics.

Because it is derived from lauric acid, it may not be fungal acne safe.

Learn more about Polysorbate 20

Sh-Oligopeptide-1

Skin Conditioning

sh-Oligopeptide-1 is a peptide found naturally in our bodies. Peptides are the building blocks for collagen and elastin in our skin.

In cosmetics, this ingredient is bioengineered to be identical to a human gene that codes for epidermal growth factor (EGF). EGF are signal molecules that simulate cell growth and healing.

Studies find EGF help with:

In South Korea and China, EGF is considered a controversial ingredient. The South Korean Ministry of Food and Drug Safety has cracked down on companies with products including EGF due to false advertisement claims.

According to Dr. Zoe Draelos, growth factors have some drawbacks:

There is also controversy surrounding growth factors. The controversy is due to their mitogenic activity, or their ability to increase the number of cells. It is best to avoid using growth factors if you have psoriasis or are at risk of skin cancer. However, it should be noted EGF are not mutagenic - meaning they will not cause cancer.

Learn more about Sh-Oligopeptide-1

Sh-Polypeptide-1

Skin Conditioning

Sh-Polypeptide-1 is a signal peptide that tells our cells to create more fibroblast cells. Fibroblasts maintain skin structure and plays a role in wound healing.

It is important to note this ingredient is mitogenic and not mutagenic. Meaning it will stimulate cell multiplication, and will not cause cancer.

Sh-Polypeptide-9

Skin Conditioning

Sh-Polypeptide-9 is a signal peptide that tells our body to create more blood vessels.

It is important to note, this ingredient is mitogenic and not mutagenic. Meaning it will stimulate cell multiplication, and will not cause cancer.

Tromethamine

Buffering, Masking

Tromethamine (aka THAM) is a synthetic amino acid that shows up in skincare as a helper ingredient.

It functions as a pH adjuster to help neutralize acidic ingredients and set a formula's pH to the right spot.

This matters a lot because a lot of actives (like vitamin C) needs a specific pH to work well and feel comfortable on skin.

Concentration use ranges from 0.1-1.0% depending on the formula.

Learn more about Tromethamine

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

Xanthan Gum

Emulsifying, Emulsion Stabilising, Gel Forming

Xanthan 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 Gum