Kiehl's Powerful-Strength Dark Circle Reducing Vitamin C Eye Serum Versus Dr. Dennis Gross Skincare C+ Collagen Brighten & Firm Vitamin C Serum

Kiehl's Powerful-Strength Dark Circle Reducing Vitamin C Eye Serum Versus Dr. Dennis Gross Skincare C+ Collagen Brighten & Firm Vitamin C Serum

This brightening eye moisturizer is formulated around Ascorbic Acid and Adenosine to fade the look of dark spots and soften the look of wrinkles.

This brightening serum is formulated around 3-O-Ethyl Ascorbic Acid and Niacinamide to brighten dull-looking skin and soften the look of wrinkles.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Propylene Glycol

Dimethicone

Glycerin

Ascorbic Acid

Dimethicone Crosspolymer

Cetyl PEG/PPG-10/1 Dimethicone

Cyclohexasiloxane

Water

Hydroxyethylpiperazine Ethane Sulfonic Acid

Lauroyl Lysine

Aluminum Starch Octenylsuccinate

Polysilicone-11

CI 77891

Adenosine

Hydrolyzed Hyaluronic Acid

Steareth-20

Chlorhexidine Digluconate

N-Hydroxysuccinimide

Sodium Citrate

Potassium Sorbate

Palmitoyl Tripeptide-1

Chrysin

Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate

Palmitoyl Tetrapeptide-7

Citric Acid

Biotin

Propylene Glycol, Dimethicone, Glycerin, Ascorbic Acid, Dimethicone Crosspolymer, Cetyl PEG/PPG-10/1 Dimethicone, Cyclohexasiloxane, Water, Hydroxyethylpiperazine Ethane Sulfonic Acid, Lauroyl Lysine, Aluminum Starch Octenylsuccinate, Polysilicone-11, CI 77891, Adenosine, Hydrolyzed Hyaluronic Acid, Steareth-20, Chlorhexidine Digluconate, N-Hydroxysuccinimide, Sodium Citrate, Potassium Sorbate, Palmitoyl Tripeptide-1, Chrysin, Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate, Palmitoyl Tetrapeptide-7, Citric Acid, Biotin

3-O-Ethyl Ascorbic Acid

Niacinamide

Glycereth-7 Triacetate

Lactic Acid

Sd Alcohol 40-B

Hydroxyethylcellulose

Dimethyl Isosorbide

Collagen Amino Acids

Superoxide Dismutase

Glycine

Carnitine Hcl

Ubiquinone

Hexylresorcinol

Emblica Officinalis Fruit Extract

Hydrolyzed Soy Protein

Tetrahexyldecyl Ascorbate

Isoquercetin

Mandelic Acid

Pueraria Lobata Root Extract

Curcuma Longa Root Extract

Phytic Acid

Tetrasodium EDTA

Butylene Glycol

Xanthan Gum

Polysorbate 20

T-Butyl Alcohol

Sodium Hydroxide

Polysorbate 80

Denatonium Benzoate

Benzyl Alcohol

Phenoxyethanol

Sodium Benzoate

Water, Glycerin, 3-O-Ethyl Ascorbic Acid, Niacinamide, Glycereth-7 Triacetate, Lactic Acid, Sd Alcohol 40-B, Hydroxyethylcellulose, Dimethyl Isosorbide, Ascorbic Acid, Collagen Amino Acids, Superoxide Dismutase, Glycine, Carnitine Hcl, Ubiquinone, Hexylresorcinol, Emblica Officinalis Fruit Extract, Hydrolyzed Soy Protein, Tetrahexyldecyl Ascorbate, Isoquercetin, Mandelic Acid, Pueraria Lobata Root Extract, Curcuma Longa Root Extract, Phytic Acid, Citric Acid, Tetrasodium EDTA, Sodium Citrate, Butylene Glycol, Xanthan Gum, Polysorbate 20, T-Butyl Alcohol, Sodium Hydroxide, Polysorbate 80, Denatonium Benzoate, Benzyl Alcohol, Phenoxyethanol, Sodium Benzoate, Potassium Sorbate

Alternatives

Ingredients Explained

These ingredients are found in both products.

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

Ascorbic Acid is is pure Vitamin C and is the biologically active form used directly by skin.

Not only is vitamin C great for your overall health and immune system, but it also has plenty of benefits for your skin. It is best supported by academic literature for:

Topical vitamin C has been shown to help neutralize oxidative stress from UV and pollution, helping to improve photoaging and hyperpigmentation when used consistently.

One clinical study found that using 5% topical vitamin C for six months improved signs of photodamaged skin, both on the surface and in the deeper structural layers of the skin.

While vitamin C doesn’t replace sunscreen, studies show it can boost photoprotection when combined with Vitamin E and ferulic acid. These two ingredients help improve stability and protective effects.

The big downside of this ingredient is formulation difficulty. Vitamin C is prone to oxidation and doesn't penetrate the skin unless formulated correctly. Research found that vitamin C absorbs into the skin best at a low pH (< 3.5) with about 20% being the upper limit for effective absorption.

Skin levels can saturate after repeated application; this means your skin won’t keep absorbing more once it’s full of vitamin C. This is why more isn’t always better with vitamin C and why very high concentrations don’t necessarily give extra benefits.

Ascorbic acid generally works well with many skincare ingredients but can be irritating when combined with other active ingredients. Strong oxidizing acne treatments like benzoyl peroxide can reduce the effectiveness of vitamin C if they are used at the same time; they are often recommended for use at different times of day.

Read more about other types of Vitamin C:

Foods rich with vitamin C include oranges, strawberries, broccoli, bell peppers, and more. When consuming Vitamin C, your skin receives a portion of the nutrients.

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.

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.

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 Citrate is the sodium salts of citric acid. In skincare, it is used to alter pH levels and acts as a preservative.

Its main functions are to maintain the pH of a product and neutralize metal ions.

The acidity of our skin is maintained by our glands and skin biome; normal pH level of skin is slightly acidic (~4.75-5.5).

Being slightly acidic allows our skin to create an "acid mantle". This acid mantle is a thin barrier that protects our skin from bacteria and contaminants.

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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