Paula's Choice CellularYouth Longevity Serum Versus Medik8 Liquid Peptides Advanced MP

Paula's Choice CellularYouth Longevity Serum Versus Medik8 Liquid Peptides Advanced MP

This hydrating serum is formulated around Simmondsia Chinensis Seed Oil and Bacillus Ferment to hydrate skin and strengthen the skin barrier.

This anti-aging serum is formulated around Palmitoyl Tripeptide-38 and Palmitoyl Tripeptide-5 to soften the look of wrinkles and refine skin texture.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Propanediol

Glycerin

Triheptanoin

Methyl Gluceth-20

Simmondsia Chinensis Seed Oil

Tridecyl Trimellitate

Maltodextrin

1,2-Hexanediol

Dimethicone

Taurine

Bacillus Ferment

Ganoderma Lucidum Stem Extract

Helianthus Annuus Sprout Extract

Lycium Barbarum Fruit Extract

Acetyl Tetrapeptide-2

Isomalt

Coco-Caprylate/Caprate

Hydroxyacetophenone

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

C9-12 Alkane

Dilinoleic Acid/Butanediol Copolymer

Glyceryl Behenate

Polyglyceryl-6 Octastearate

Sodium Phytate

Acrylates/C10-30 Alkyl Acrylate Crosspolymer

Potassium Chloride

Acacia Senegal Gum

Xanthan Gum

Polysorbate 60

Sorbitan Isostearate

Synthetic Fluorphlogopite

Caprylyl Glycol

Citric Acid

Castor Oil/Ipdi Copolymer

Lecithin

Cyanocobalamin

Tin Oxide

CI 77491

CI 77891

Water, Propanediol, Glycerin, Triheptanoin, Methyl Gluceth-20, Simmondsia Chinensis Seed Oil, Tridecyl Trimellitate, Maltodextrin, 1,2-Hexanediol, Dimethicone, Taurine, Bacillus Ferment, Ganoderma Lucidum Stem Extract, Helianthus Annuus Sprout Extract, Lycium Barbarum Fruit Extract, Acetyl Tetrapeptide-2, Isomalt, Coco-Caprylate/Caprate, Hydroxyacetophenone, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, C9-12 Alkane, Dilinoleic Acid/Butanediol Copolymer, Glyceryl Behenate, Polyglyceryl-6 Octastearate, Sodium Phytate, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Potassium Chloride, Acacia Senegal Gum, Xanthan Gum, Polysorbate 60, Sorbitan Isostearate, Synthetic Fluorphlogopite, Caprylyl Glycol, Citric Acid, Castor Oil/Ipdi Copolymer, Lecithin, Cyanocobalamin, Tin Oxide, CI 77491, CI 77891

Dimethyl Isosorbide

Butylene Glycol

Undecane

Arginine

Inulin

Microcrystalline Cellulose

Ceteareth-20

Tridecane

Tocopherol

Sodium Hyaluronate

Palmitoyl Tripeptide-38

Panthenol

Caprylic/Capric Triglyceride

Palmitoyl Tripeptide-5

Polyacrylate Crosspolymer-6

Palmitoyl Tripeptide-1

Pullulan

Tetrapeptide-21

Palmitoyl Tetrapeptide-10

Palmitoyl Tetrapeptide-7

Ammonium Polyacryloyldimethyl Taurate

Glyceryl Linoleate

Acetyl Hexapeptide-8

Pentapeptide-18

Oligopeptide-1

Arginine/Lysine Polypeptide

Sucrose Palmitate

Cetyl Palmitate

Phenoxyethanol

Ethylhexylglycerin

Carbomer

Copper Palmitoyl Heptapeptide-14

Heptapeptide-15 Palmitate

Benzotriazolyl Dodecyl P-Cresol

Polysorbate 80

Sorbitan Stearate

Polysorbate 20

Carnosine

Sodium Metabisulfite

Dunaliella Salina Extract

Helianthus Annuus Seed Oil

Hydroxypropyl Cyclodextrin

Dimethicone/Vinyl Dimethicone Crosspolymer

Sodium Benzoate

Hydrogenated Lecithin

Pantolactone

Disodium EDTA

T-Butyl Alcohol

Potassium Sorbate

Glyceryl Caprylate

Lactic Acid/Glycolic Acid Copolymer

Polyvinyl Alcohol

Phenylpropanol

Water, Glycerin, Dimethicone, Dimethyl Isosorbide, Butylene Glycol, Undecane, Arginine, Inulin, Microcrystalline Cellulose, Ceteareth-20, Tridecane, Tocopherol, Hydroxyacetophenone, Sodium Hyaluronate, Palmitoyl Tripeptide-38, Panthenol, Caprylic/Capric Triglyceride, Palmitoyl Tripeptide-5, Polyacrylate Crosspolymer-6, Palmitoyl Tripeptide-1, Pullulan, Tetrapeptide-21, Palmitoyl Tetrapeptide-10, Palmitoyl Tetrapeptide-7, Ammonium Polyacryloyldimethyl Taurate, Glyceryl Linoleate, Acetyl Hexapeptide-8, Pentapeptide-18, Oligopeptide-1, Arginine/Lysine Polypeptide, Sucrose Palmitate, Cetyl Palmitate, Phenoxyethanol, Ethylhexylglycerin, Carbomer, Copper Palmitoyl Heptapeptide-14, Heptapeptide-15 Palmitate, Benzotriazolyl Dodecyl P-Cresol, Polysorbate 80, Sorbitan Stearate, Polysorbate 20, Carnosine, Sodium Metabisulfite, Dunaliella Salina Extract, Helianthus Annuus Seed Oil, Hydroxypropyl Cyclodextrin, Dimethicone/Vinyl Dimethicone Crosspolymer, Sodium Benzoate, Hydrogenated Lecithin, Caprylyl Glycol, Pantolactone, Xanthan Gum, Disodium EDTA, T-Butyl Alcohol, Potassium Sorbate, Citric Acid, Glyceryl Caprylate, Lactic Acid/Glycolic Acid Copolymer, Polyvinyl Alcohol, Phenylpropanol

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Alternatives

Ingredients Explained

These ingredients are found in both products.

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

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

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.

However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.

Due to this, citric acid is usually included in small amounts as a pH adjuster. This helps keep products slightly more acidic and compatible with skin's natural pH.

In skincare formulas, citric acid can:

While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.

Most citric acid used in skincare today is made by fermenting sugars (usually from molasses). This synthetic version is identical to the natural citrus form but easier to stabilize and use in formulations.

Rosacea skin has a lower threshold for acids generally, with 62.5% of rosacea subjects in one study reacting to lactic acid in a sting test. This is why we mark citric acid as a potential rosacea trigger.

However, this ingredient shows up as a pH adjuster or chelator at roughly 0.1-1% in many products. These low levels are unlikely to be an issue for rosacea skin and becomes a potential trigger at exfoliating concentrations (20%). Because everybody's skin is unique, we recommend a patch test if you are unsure.

Dimethicone is a type of synthetic silicone created from natural materials such as quartz. It is also known as polydimethylsiloxane.

What it does:

Dimethicone comes in different viscosities:

Depending on the viscosity, dimethicone has different properties.

Ingredients lists don't always show which type is used, so we recommend reaching out to the brand if you have questions about the viscosity.

This ingredient is unlikely to cause irritation because it does not get absorbed into skin. However, people with silicone allergies should be careful about using this ingredient.

Note: Dimethicone may contribute to pilling. This is because it is not oil or water soluble, so pilling may occur when layered with products. When mixed with heavy oils in a formula, the outcome is also quite greasy.

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.

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.

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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