Peter Thomas Roth Peptide 21 Wrinkle Resist Serum Versus Medik8 Liquid Peptides
Updated on February 06, 2025
Overview
What they are
These products are both reef safe serums. They have a total of 15 ingredients in common
Cool Features
They both contain hyaluronic acid and peptides
Suited For
They're both likely to be good for anti aging, dry skin, brightening skin, oily skin, reducing pores, scar healing, dark spots and better texture
Free From
They both do not contain any harsh alcohols, common allergens, oils or parabens
We independently verify ingredients, and our claims are backed by peer-reviewed research. Spot a product that needs an update? Let us know.
Ingredient Info
Peter Thomas Roth Peptide 21 Wrinkle Resist Serum 56 ingredients
Medik8 Liquid Peptides 33 ingredients
What's inside (and what isn't)
What's inside (and what isn't)
At a glance
Click on any of the items below to learn more
Peter Thomas Roth Peptide 21 Wrinkle Resist Serum 56 ingredients
Medik8 Liquid Peptides 33 ingredients
Key Ingredients
Benefits
Concerns
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
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, commonly known as Argireline, is a popular peptide in skincare. It’s often referred to as a “Botox-like” ingredient because it helps reduce muscle movement.
By relaxing these micro-movements, Argireline may help minimize the appearance of fine lines and wrinkles. That said, it’s not as powerful as Botox, and research on its long-term effectiveness is still limited.
Beyond smoothing, Argireline may also support collagen production. Collagen is the protein that helps keep your skin firm, bouncy, and well-hydrated by strengthening the skin barrier.
So while Argireline isn’t a miracle fix, it can be a helpful addition to a routine focused on both prevention and skin health.
Read more about other common types of peptides here:
Learn more about Acetyl Hexapeptide-8Butylene 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 GlycolCaprylyl Glycol is a humectant and emollient, meaning it attracts and preserves moisture.
It is a common ingredient in many products, especially those designed to hydrate skin. The primary benefits are retaining moisture, skin softening, and promoting a healthy skin barrier.
Though Caprylyl Glycol is an alcohol derived from fatty acids, it is not the kind that can dry out skin.
This ingredient is also used as a preservative to extend the life of products. It has slight antimicrobial properties.
Learn more about Caprylyl GlycolCarbomer is a polymer of acrylic acid. Its main role is to create a gel consistency.
A high amount of carbomer can cause pilling or balling up of products. Don't worry, most products contain 1% or less of carbomer.
Glycerin is already naturally found in your skin. It helps moisturize and protect your skin.
A study from 2016 found glycerin to be more effective as a humectant than AHAs and hyaluronic acid.
As a humectant, it helps the skin stay hydrated by pulling moisture to your skin. The low molecular weight of glycerin allows it to pull moisture into the deeper layers of your skin.
Hydrated skin improves your skin barrier; Your skin barrier helps protect against irritants and bacteria.
Glycerin has also been found to have antimicrobial and antiviral properties. Due to these properties, glycerin is often used in wound and burn treatments.
In cosmetics, glycerin is usually derived from plants such as soybean or palm. However, it can also be sourced from animals, such as tallow or animal fat.
This ingredient is organic, colorless, odorless, and non-toxic.
Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.
Learn more about GlycerinPalmitoyl Tetrapeptide-7 is a lab-made peptide with anti-inflammatory and skin-repairing benefits. It's made up of four amino acids (glycine, glutamine, proline, and arginine) and palmitic acid (which helps it penetrate skin more effectively).
This ingredient helps reduce inflammation by limiting the production of interleukin-6 (IL-6), a chemical that triggers inflammatory responses, particularly after UV exposure.
Less inflammation = slower collagen breakdown and a longer-lasting, youthful appearance.
Palmitoyl Tetrapeptide-7 also stimulates collagen production and supports a healthier skin barrier.
Over time, this can improve skin firmness, hydration, and reduce the appearance of fine lines. It’s commonly paired with Palmitoyl Tripeptide-1 in the well-known Matrixyl 3000 complex for enhanced anti-aging effects.
This ingredient has been shown to be effective and safe in cosmetic use and you'll typically find it in small amounts (less than 0.01%).
Due to its palmitic acid base, it may not be safe for Malassezia folliculitis.
Read more about other common types of peptides here:
Learn more about Palmitoyl Tetrapeptide-7Palmitoyl Tripeptide-1 is also known as pal-GHK. It is made up of 3 amino acids and palmitic acid, a fatty acid that helps it absorb into skin more easily.
This peptide is as a signal peptide, meaning it tells the skin to produce more collagen. Collagen is the key protein that helps form the skin's structure and keep it plump, firm, and hydrated.
By boosting collagen production, this ingredient supports a stronger skin barrier and helps reduce the appearance of wrinkles.
You'll most likely see this ingredient paired with Palmitoyl Tetrapeptide-7 in the well-known Matrixyl 3000 complex. While results from in-house testing should be viewed cautiously, this peptide duo is among the most studied and widely used in modern skincare.
Due to its palmitic acid base, this ingredient may not be safe for Malassezia folliculitis.
Read more about other common types of peptides here:
Learn more about Palmitoyl Tripeptide-1This synthetic peptide is created from lysine, valine, and palmitic acid.
According to the manufacturer, in-vitro studies show tissue growth and collagen synthesis. Another in-vivo study found 60 volunteers saw a significant reduction in wrinkles after 84 days.
Due to its palmitic acid base, this peptide may not be fungal-acne safe.
Learn more about Palmitoyl Tripeptide-5Phenoxyethanol is a preservative that has germicide, antimicrobial, and aromatic properties. Studies show that phenoxyethanol can prevent microbial growth. By itself, it has a scent that is similar to that of a rose.
It's often used in formulations along with Caprylyl Glycol to preserve the shelf life of products.
Polysorbate 20 is made by combining ethoxylation of sorbitan, ethylene oxide, and lauric acid. It is a mild cleansing agent, surfactant, and emulsifier.
As a surfactant, it helps collect dirt and oils for washing. Emulsifiers prevent oils and water from separating.
Polysorbate 20 also adds scent to a product. Since it is made using sorbitol, it has a sweet scent. Sorbitol can also be found in fruits such as apples and peaches.
The lauric acid used to create Polysorbate 20 is often derived from coconuts.
Polysorbate 20 may not be fungal acne safe.
Learn more about Polysorbate 20Potassium 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.
Learn more about Potassium SorbateSodium 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.
Learn more about Sodium BenzoateSodium Hyaluronate is hyaluronic acid's salt form. It is commonly derived from the sodium salt of hyaluronic acid.
Like hyaluronic acid, it is great at holding water and acts as a humectant. This makes it a great skin hydrating ingredient.
Sodium Hyaluronate is naturally occurring in our bodies and is mostly found in eye fluid and joints.
These are some other common types of Hyaluronic Acid:
Learn more about Sodium HyaluronateWater. 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. Stay hydrated!
Learn more about WaterXanthan 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 GumIngredient Ratings
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Peter Thomas Roth Peptide 21 Wrinkle Resist Serum 56 ingredients
Medik8 Liquid Peptides 33 ingredients

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