Medik8 C-Tetra™ Advanced Gel-Serum Versus IMAGE skincare Vital C Hydrating Anti-Aging Serum

Medik8 C-Tetra™ Advanced Gel-Serum Versus IMAGE skincare Vital C Hydrating Anti-Aging Serum

This brightening serum is formulated around Tetrahexyldecyl Ascorbate and Acetyl Glucosamine to brighten dull-looking skin and soften the look of wrinkles.

This hydrating serum is formulated around Aloe Barbadensis Leaf Juice and Magnesium Ascorbyl Phosphate to hydrate skin.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Tetrahexyldecyl Ascorbate

Isododecane

Propanediol

Acetyl Glucosamine

Squalane

Tocopherol

Acetyl Zingerone

Camellia Sinensis Leaf

Hydroxyacetophenone

Sodium Hyaluronate

Cellulose

Avena Sativa Kernel Extract

Glycerin

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Citrus Grandis Peel Oil

Sucrose Stearate

Tetrasodium Glutamate Diacetate

Ethylhexylglycerin

Acrylates/C10-30 Alkyl Acrylate Crosspolymer

Xanthan Gum

Sodium Benzoate

Cellulose Gum

1,2-Hexanediol

Polysorbate 60

Sorbitan Isostearate

Citric Acid

Phenoxyethanol

Citral

Linalool

Limonene

Water, Tetrahexyldecyl Ascorbate, Isododecane, Propanediol, Acetyl Glucosamine, Squalane, Tocopherol, Acetyl Zingerone, Camellia Sinensis Leaf, Hydroxyacetophenone, Sodium Hyaluronate, Cellulose, Avena Sativa Kernel Extract, Glycerin, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Citrus Grandis Peel Oil, Sucrose Stearate, Tetrasodium Glutamate Diacetate, Ethylhexylglycerin, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Xanthan Gum, Sodium Benzoate, Cellulose Gum, 1,2-Hexanediol, Polysorbate 60, Sorbitan Isostearate, Citric Acid, Phenoxyethanol, Citral, Linalool, Limonene

Aloe Barbadensis Leaf Juice

Citrus Aurantium Dulcis Oil

Caprylic/Capric Triglyceride

C12-15 Alkyl Benzoate

Cetearyl Olivate

Sorbitan Olivate

Imperata Cylindrica Root Extract

Magnesium Ascorbyl Phosphate

PPG-12/Smdi Copolymer

Glyceryl Stearate

PEG-100 Stearate

Cetyl Alcohol

Dimethicone

Di-PPG-2 Myreth-10 Adipate

Stearic Acid

Ethylhexyl Methoxycinnamate

Panthenol

Prunus Amygdalus Dulcis Oil

Caprylyl Glycol

Butylene Glycol

Tocopheryl Acetate

Glycine Soja Sterols

Linoleic Acid

Phospholipids

Simmondsia Chinensis Seed Oil

Squalene

Propylene Glycol

Glucosamine Hcl

Hexylene Glycol

Linoleamidopropyl Pg-Dimonium Chloride Phosphate

PEG-8

Pisum Sativum Extract

Citrus Nobilis Peel Oil

Dipotassium Glycyrrhizate

Phyllanthus Emblica Fruit Extract

Stearyl Glycyrrhetinate

Bambusa Vulgaris Leaf/Stem Extract

Magnesium Aluminum Silicate

Olea Europaea Leaf Extract

Disodium EDTA

Eugenia Caryophyllus Leaf Oil

Yeast Polysaccharides

Glyceryl Polymethacrylate

Carbomer

Eugenol

Ascorbyl Palmitate

Benzoic Acid

Camellia Sinensis Leaf Extract

Ascorbic Acid

Sodium Lactate

Polysorbate 20

Spiraea Ulmaria Flower Extract

Taurine

Corallina Officinalis Extract

Vitis Vinifera Seed Extract

Centella Asiatica Flower/Leaf/Stem Extract

Centella Asiatica Extract

Potassium Sorbate

BHT

Acetyl Hexapeptide-8

Darutoside

Palmitoyl Pentapeptide-4

Arginine

Leucine

Lysine

Valine

Palmitoyl Tripeptide-1

Aloe Barbadensis Leaf Juice, Water, Glycerin, Citrus Aurantium Dulcis Oil, Caprylic/Capric Triglyceride, Limonene, C12-15 Alkyl Benzoate, Cetearyl Olivate, Sorbitan Olivate, Imperata Cylindrica Root Extract, Magnesium Ascorbyl Phosphate, PPG-12/Smdi Copolymer, Tetrahexyldecyl Ascorbate, Glyceryl Stearate, PEG-100 Stearate, Cetyl Alcohol, Dimethicone, Di-PPG-2 Myreth-10 Adipate, Stearic Acid, Phenoxyethanol, Ethylhexyl Methoxycinnamate, Panthenol, Prunus Amygdalus Dulcis Oil, Xanthan Gum, Caprylyl Glycol, Butylene Glycol, Tocopheryl Acetate, Glycine Soja Sterols, Linoleic Acid, Phospholipids, Simmondsia Chinensis Seed Oil, Squalene, Propylene Glycol, Ethylhexylglycerin, Glucosamine Hcl, Hexylene Glycol, Linoleamidopropyl Pg-Dimonium Chloride Phosphate, PEG-8, Pisum Sativum Extract, Citrus Nobilis Peel Oil, Dipotassium Glycyrrhizate, Phyllanthus Emblica Fruit Extract, Stearyl Glycyrrhetinate, Bambusa Vulgaris Leaf/Stem Extract, Tocopherol, Magnesium Aluminum Silicate, Olea Europaea Leaf Extract, Disodium EDTA, Eugenia Caryophyllus Leaf Oil, Yeast Polysaccharides, Sodium Hyaluronate, Glyceryl Polymethacrylate, Carbomer, Eugenol, Ascorbyl Palmitate, Citric Acid, Benzoic Acid, Camellia Sinensis Leaf Extract, Ascorbic Acid, Sodium Lactate, Polysorbate 20, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Spiraea Ulmaria Flower Extract, Taurine, Corallina Officinalis Extract, Vitis Vinifera Seed Extract, Centella Asiatica Flower/Leaf/Stem Extract, Centella Asiatica Extract, Potassium Sorbate, BHT, Acetyl Hexapeptide-8, Darutoside, Palmitoyl Pentapeptide-4, Arginine, Leucine, Lysine, Sodium Benzoate, Valine, Palmitoyl Tripeptide-1

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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.

Acrylates/C10-30 Alkyl Acrylate Crosspolymer is a synthetic polymer. It is used to thicken, emulsify, and improve the texture of products.

As an emulsifier, it helps stabilize oil-in-water emulsions to give products an elegant feel when applied.

It can also form a thin protective film on skin. One study found that a formula using this polymer helped slow down how quickly other ingredients (like DEET) were absorbed through skin.

A 2024 study of over 1,300 patients confirmed that sensitization to this ingredient is rare. It is also non-mutagenic and has a clean track record.

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.

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.

Limonene is a fragrance that adds scent and taste to a formulation.

It's found in the peel oil of citrus fruits and other plants such as lavender and eucalyptus. The scent of limonene is generally described as "sweet citrus".

Limonene acts as an antioxidant, meaning it helps neutralize free radicals.

When exposed to air, oxidized limonene may sensitize the skin. Because of this, limonene is often avoided by people with sensitive skin.

The term 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term. For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance.

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.

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.

Tetrahexyldecyl Ascorbate (THD) is a stable and oil-soluble form of Vitamin C.

THD is special in that it has the ability to travel deeper into skin than traditional ascorbic acid while maintaining the same skin benefits (double win!).

Because it’s oil-soluble, THD dives deep into your skin’s fatty layers (think ceramides and cholesterol) to fight off the kind of free radicals that mess with your skin barrier. This makes it a great pair with water-based vitamin C (ascorbic acid) that mainly works on the surface.

Even at just 0.1%, THD is already showing great antioxidant activity. When used up to 2%, it helps keep your skin happy and calm, especially when it’s stressed from pollution or sun.

Want to fade dark spots or tackle hyperpigmentation? You’ll want 5% or more. Pairing it with brightening buddies like niacinamide or licorice root gives even better results. One study even used 30% THD with other brighteners and saw real results on stubborn discoloration, even in melasma-prone skin.

A note on THD: It’s has a slightly silky, oily texture and usually shows up colorless or pale yellow (though the exact shade can vary by supplier).

While you can sneak it into water-based formulas, it really shines when paired with silicones or oils, which help your skin soak it up better.

THD is pretty stable, but it’s still vulnerable to degradation like ascorbic acid. Too much light or heat (above 113°F / 45°C) can break it down over time. Go for dark and opaque packaging that keeps it safe and shady!

Read more about other types of Vitamin C:

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!

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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