Dear, Klairs Fundamental Watery Oil Drop Versus COSRX The 6 Peptide Skin Booster Serum

Dear, Klairs Fundamental Watery Oil Drop Versus COSRX The 6 Peptide Skin Booster Serum

This hydrating serum is formulated around Bifida Ferment Extract and Oryza Sativa Extract to hydrate skin and strengthen the skin barrier.

This anti-aging serum is formulated around Niacinamide and Acetyl Hexapeptide-8 to soften the look of wrinkles and strengthen the skin barrier.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Glycerin

Butylene Glycol

Camellia Sinensis Leaf Water

Bifida Ferment Extract

Oryza Sativa Extract

Dipropylene Glycol

Betaine

1,2-Hexanediol

Aspergillus/Rice Ferment Extract

Camellia Sinensis Leaf Extract

Sorbitol

Sorbitan Sesquioleate

Ethylhexylglycerin

Arginine

Xanthan Gum

Hydroxyethylcellulose

Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Isohexadecane

Dipotassium Glycyrrhizate

Sodium Hyaluronate

Carbomer

Acrylates/C10-30 Alkyl Acrylate Crosspolymer

Tocopheryl Acetate

Laminaria Japonica Extract

Polysorbate 80

Sorbitan Oleate

Hydrogenated Lecithin

Ceramide NP

Disodium Phosphate

Polysorbate 60

Sodium Phosphate

Copper Tripeptide-1

Acetyl Hexapeptide-8

Water, Glycerin, Butylene Glycol, Camellia Sinensis Leaf Water, Bifida Ferment Extract, Oryza Sativa Extract, Dipropylene Glycol, Betaine, 1,2-Hexanediol, Aspergillus/Rice Ferment Extract, Camellia Sinensis Leaf Extract, Sorbitol, Sorbitan Sesquioleate, Ethylhexylglycerin, Arginine, Xanthan Gum, Hydroxyethylcellulose, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Isohexadecane, Dipotassium Glycyrrhizate, Sodium Hyaluronate, Carbomer, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Tocopheryl Acetate, Laminaria Japonica Extract, Polysorbate 80, Sorbitan Oleate, Hydrogenated Lecithin, Ceramide NP, Disodium Phosphate, Polysorbate 60, Sodium Phosphate, Copper Tripeptide-1, Acetyl Hexapeptide-8

Pentylene Glycol

Niacinamide

Sh-Polypeptide-121

Dipeptide Diaminobutyroyl Benzylamide Diacetate

Oligopeptide-68

Palmitoyl Tripeptide-8

Allantoin

Acetyl Glucosamine

Serine

Alanine

Glycine

Threonine

Proline

Sodium PCA

Sodium Lactate

PCA

Glutamic Acid

Lysine Hcl

Tocopherol

Dextran

Glycine Soja Oil

Ammonium Acryloyldimethyltaurate/Vp Copolymer

Polyacrylate Crosspolymer-6

Adenosine

Polyquaternium-51

Disodium EDTA

Citric Acid

Caprylyl Glycol

T-Butyl Alcohol

Potassium Sorbate

Sodium Oleate

Water, Dipropylene Glycol, Glycerin, Pentylene Glycol, 1,2-Hexanediol, Niacinamide, Acetyl Hexapeptide-8, Copper Tripeptide-1, Sh-Polypeptide-121, Dipeptide Diaminobutyroyl Benzylamide Diacetate, Oligopeptide-68, Palmitoyl Tripeptide-8, Allantoin, Sodium Hyaluronate, Acetyl Glucosamine, Serine, Alanine, Glycine, Threonine, Arginine, Proline, Betaine, Sodium PCA, Sodium Lactate, PCA, Glutamic Acid, Lysine Hcl, Tocopherol, Dextran, Glycine Soja Oil, Hydrogenated Lecithin, Ammonium Acryloyldimethyltaurate/Vp Copolymer, Polyacrylate Crosspolymer-6, Butylene Glycol, Xanthan Gum, Ethylhexylglycerin, Adenosine, Polyquaternium-51, Disodium EDTA, Citric Acid, Caprylyl Glycol, T-Butyl Alcohol, Potassium Sorbate, Sodium Oleate

Reviews

Alternatives

Ingredients Explained

These ingredients are found in both products.

Ingredients higher up in an ingredient list are typically present in a larger amount.

1,2-Hexanediol is a synthetic liquid and another multi-functional powerhouse.

It is a:

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

Acetyl Hexapeptide-8 (also known as Argireline) is a synthetic hexapeptide that is often called a "topical Botox alternative".

It works by mimicking how Botox relaxes muscles; it interferes with the signaling process that tells your facial muscles to contract. This can help soften expression lines like forehead wrinkles or crow's feet over time.

The comparison to Botox does have limits because the molecule is water-loving and relatively large.

Acetyl Hexapeptide-8 has a hard time absorbing deeply enough through the skin's outer barrier to actually reach the muscles.

So whether it truly works the way Botox does at a biological level is still up for debate, but early clinical outcomes are fairly encouraging.

A 12 week human study of a multi-ingredient regimen containing this ingredient saw:

While some studies have observed improvements in wrinkle appearance, it is important to note that more consistent results are seen in multi-ingredient formulations (vs just Acetyl Hexapeptide-8 alone).

Some research studies also used higher concentrations (up to 10%) while this ingredient is usually found in concentrations up to 0.005% in leave-on formulations.

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.

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.

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.

Copper Tripeptide-1 (GHK-Cu) is a skin repairing ingredient known for its ability to boost collagen, improve firmness, and support skin regeneration.

It is a complex made up of a naturally occurring peptide (glycine-histidine-lysine) and copper, an essential trace element.

While studying wound healing, researchers noticed GHK-Cu stimulated hair follicle enlargement and growth by keeping hair in its active growth phase longer. This has made it a promising ingredient for hair regrowth treatments.

Some people have reported increased facial hair. While GHK-Cu can make your hair follicles bigger, it usually doesn’t turn soft, barely-visible facial hairs into thick, dark ones.

Anecdotal reports suggest that overusing copper peptides might lead to premature aging due to excess free copper or enzyme imbalances. This claim isn’t backed by large-scale studies.

Unfortunately, there are limited human studies for this ingredient. While early results are promising, many studies are either small, in-vitro, or not rigorously controlled.

For example, there is a 1998 study that explored the effects of copper tripeptide, vitamin C, tretinoin, and melatonin on skin repair and collagen synthesis.

After one month, increased procollagen production was seen in 7 out of 10 participants using copper tripeptide (more than those using vitamin C, melatonin, or tretinoin.

While the study was exploratory, it offers early evidence that copper tripeptide may support collagen production. Larger, well-designed trials are still needed to confirm its potential and understand individual responses.

Read more about other common types of peptides here:

Dipropylene Glycol is a synthetically created humectant, stabilizer, and solvent.

This ingredient helps:

Dipropylene glycol is technically an alcohol, but it belongs to the glycol family (often considered part of the ‘good’ alcohols). This means it is hydrating and gentle on skin unlike drying solvent alcohols like denatured alcohol.

As a masking agent, Dipropylene Glycol can be used to cover the smell of other ingredients. However, it does not have a scent.

Studies show Dipropylene Glycol is considered safe to use in skincare.

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.

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.

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).

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.

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!

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.

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