Medik8 Liquid Peptides Advanced MP Versus Peter Thomas Roth Peptide Skinjection Amplified Wrinkle-Fix Serum

Medik8 Liquid Peptides Advanced MP Versus Peter Thomas Roth Peptide Skinjection Amplified Wrinkle-Fix Serum

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

This anti-aging serum is formulated around Acetyl Hexapeptide-8 and Pentapeptide-18 to soften the look of wrinkles.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

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

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

Squalane

Saccharomyces Lysate

Polysilicone-11

N-Prolyl Palmitoyl Tripeptide-56 Acetate

Collagen

Phytosterols

Leuconostoc/Radish Root Ferment Filtrate

Polyglyceryl-10 Myristate

Pentylene Glycol

Sodium Phytate

Sodium Hydroxide

Ethylhexyl Palmitate

Trihydroxystearin

Lauroyl Lysine

Glucomannan

Ammonium Acryloyldimethyltaurate/Vp Copolymer

Glyceryl Stearate

Stearyl Alcohol

Behenyl Alcohol

Mica

Water, Dimethicone, Squalane, Butylene Glycol, Glycerin, Saccharomyces Lysate, Polysilicone-11, Acetyl Hexapeptide-8, Pentapeptide-18, N-Prolyl Palmitoyl Tripeptide-56 Acetate, Palmitoyl Tripeptide-38, Collagen, Sodium Hyaluronate, Tocopherol, Phytosterols, Hydrogenated Lecithin, Leuconostoc/Radish Root Ferment Filtrate, Citric Acid, Caprylic/Capric Triglyceride, Polyglyceryl-10 Myristate, Pentylene Glycol, Caprylyl Glycol, Sodium Benzoate, Sodium Phytate, Sodium Hydroxide, Potassium Sorbate, Ethylhexyl Palmitate, Hydroxypropyl Cyclodextrin, Trihydroxystearin, Lauroyl Lysine, Glucomannan, Ethylhexylglycerin, Ammonium Acryloyldimethyltaurate/Vp Copolymer, Carbomer, Glyceryl Stearate, Stearyl Alcohol, Behenyl Alcohol, Mica, Phenoxyethanol

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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.

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.

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.

Caprylic/Capric Triglyceride (aka MCT Oil) is a lightweight emollient, solvent, and texture enhancer. It is considered a skin-softener by helping to prevent moisture loss.

Though it behaves like an oil, it is not technically one due to its chemical composition. One perk of this ingredient is that it is very stable, resistant to oxidation, and unlikely to go rancid.

In practice, that translates to a long shelf life and a consistently elegant skin feel.

While there is an assumption Caprylic Triglyceride can clog pores due to it being derived from coconut oil, there is no research supporting this. Just patch test if you have concerns.

Fractionated coconut oil and MCT Oil are both listed as Caprylic/Capric Triglyceride according to INCI. This is because INCI names are based on the ingredient’s final chemical composition and not its marketing name or source.

This ingredient is treated as the gold standard fungal acne safe oil. Even though it is coconut derived, the problematic lauric acid is stripped out.

This leaves just caprylic (C8) and capric (C10) acid. These chain lengths actually trend antifungal; a 2020 study found caprylic acid was enough to disrupt Malassezia furfur cell membrane, with a caprylic acid derivative damaging membrane structures at concentrations as low as 0.2%.

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).

Carbomer is a synthetic thickening and gelling agent. It's basically the ingredient that gives a lot of serums, gels, creams, and sunscreens their smooth, non-sticky texture.

Although legally permitted at very high levels, carbomers are normally used at concentrations below 1%.

It also needs to be neutralized to actually thicken, and because it is a large molecule, it doesn't really penetrate the skin barrier.

Allergy-wise, the risk is very low. Clinical studies show carbomers have low potential for skin irritation/sensitization even at concentrations up to 100%.

A 2024 UK study patch-tested 1,302 patients and found true allergy to the parent group of carbomer to be rare with no confirmed relevant reactions.

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.

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).

This ingredient is used in skincare as a delivery system.

It works by "encapsulating" active ingredients with its unique ring shape that is water-loving on the outside and oil-loving on the inside. This improves the stability and absorption of the product into the skin.

According to a manufacturer, it also offer some moisturizing effects.

This synthetic, signal peptide has unique skin conditioning properties in that is a matrikine-mimetic compound.

First of all, Palmitoyl Tripeptide-38 is a signal peptide; signal peptides tell the body to create more collagen.

What is a matrikine-mimetic compound?

This peptide has the ability to mimic matrikines in skin. Our skin created matrikines by breaking down matrix proteins into peptides.

Matrikines play a role in:

Though further research is needed, this ingredient seems pretty promising. In one study, women over the age of 40 with visible photoaging used a vitamin C serum with this ingredient for 56 days (15% ascorbid acid, 5 ppm palmitoyl tripeptide‐38). The results found improvement in skin roughness and skin tone.

This peptide is also part of the famous Matrixyl synthe’6, a blend of ingredients that also includes glycerin, water, and hydroxypropyl cyclodextrin.

This peptide is more commonly known as Leuphasyl. It has similar properties to argireline, the "botox peptide".

According to a manufacturer, Pentapeptide-18 mimics botulinum to freeze muscles and reduce the appearance of wrinkles. Their study found this 5% of this ingredient reduced wrinkles by 11%.

Combining this ingredient with Argireline showed improved results.

Phenoxyethanol is one of the most widely used preservatives in skincare (and for good reason!).

It has a large spectrum of antimicrobial activity and especially effective bacteria, yeast, and mold while only having a weak effect on your skin's natural microbiome.

On a cellular level, it disrupts the cell membranes of microbes by poking holes that make the cell leak. This shuts down the chemical reactions the microbe needs to make energy so it can no longer survive.

Another perk of this ingredient is that it stays functional across a wide pH range (3-10).

You'll often see it paired with boosters like Ethylhexylglycerin; one study showed that a 1:9 ratio of Ethylhexylglycerin to Phenoxyethanol damages bacterial membranes as effectively as doubling the Phenoxyethanol concentration on its own.

Typical use concentrations range from 0.3-1% depending on the formula, and this ingredient is capped at 1% int the EU.

Safety-wise, the fear mongering does not hold up to the evidence. The EU's Scientific Committee on Consumer Safety and FDA consider it safe as a preservative at up to 1%, including for children of all ages.

Adverse systemic effects only showed up in animal studies at exposures roughly 200x higher than what people get from cosmetics. And despite its very widespread use, this ingredient is a rare sensitizer and allergic reactions are uncommon.

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.

Both potassium sorbate and sorbic acid can be found in baked goods, cheeses, dried meats, dried fruit, ice cream, pickles, wine, yogurt, and more.

You'll often find this ingredient used with other preservatives.

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.

Sodium benzoate works as a preservative by inhibiting the growth of bacteria inside of cells. It prevents the cell from fermenting a type of sugar using an enzyme called phosphofructokinase.

It is the salt of benzoic acid. Foods containing sodium benzoate include soda, salad dressings, condiments, fruit juices, wines, and snack foods.

Studies for using ascorbic acid and sodium benzoate in cosmetics are lacking, especially in skincare routines with multiple steps.

We always recommend speaking with a professional, such as a dermatologist, if you have any concerns.

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.

Tocopherol is a fat-soluble antioxidant known as Vitamin E.

You'll find this ingredient in the vast majority of skincare (for good reason). It works to neutralize free radicals, or unstable molecules generated by UV exposure, pollution, and other environmental stressors, before they can cause oxidative damage to your skin cells.

Topically applied tocopherol has been shown to protect against UV damage by ramping up the skin's own natural defense enzymes.

It also acts as a skin conditioning agent; some studies show that regular topical use can improve the skin's water-binding capacity over 2-4 weeks.

This ingredient is especially loved for being a team player. When combined with Vitamin C, the photoprotective effect of both ingredients roughly doubles and the combo also helps reduce UV-induced DNA damage.

This ingredient has some brightening potential but it's more of a prevention ingredient than spot-fader. Cell studies show it can slow down melanin production but it's worth noting that it's not the most powerful brightener out there.

In formulations, it also serves as a stabilizer that helps protect other oxidation-prone ingredients from degrading.

Concentrations usually range from 0.1-1% in most leave-on products.

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!

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