Kiehl's Powerful-Strength Dark Circle Reducing Vitamin C Eye Serum Versus Youth To The People Peptides + C Energy Eye Concentrate

Kiehl's Powerful-Strength Dark Circle Reducing Vitamin C Eye Serum Versus Youth To The People Peptides + C Energy Eye Concentrate

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 anti-aging eye moisturizer is formulated around Ascorbyl Glucoside and Palmitoyl Tetrapeptide-7 to soften the look of wrinkles and brighten dull-looking skin.

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

Caprylic/Capric Triglyceride

Propanediol

Sodium Acrylates Copolymer

Citrus Junos Seed Oil

Panthenol

Ascorbyl Glucoside

Hylocereus Undatus Fruit Extract

Ilex Guayusa Leaf Extract

Ilex Paraguariensis Leaf Extract

Jania Rubens Extract

Lactobacillus Ferment

Maltodextrin

Malus Domestica Fruit Cell Culture Extract

Momordica Cochinchinensis Seed Extract

Punica Granatum Seed Extract

Sodium Carrageenan

Caffeine

Caprylyl Glycol

Dipeptide-2

Hesperidin Methyl Chalcone

Hydroxyacetophenone

Sodium Hyaluronate

Sodium Hydroxide

1,2-Hexanediol

Niacinamide

Tocopherol

Alcohol

Cellulose

Ethylhexylglycerin

Hydroxyethylcellulose

Lecithin

Sodium Acetate

Synthetic Fluorphlogopite

Tin Oxide

Xanthan Gum

Phenoxyethanol

Sodium Benzoate

Water, Caprylic/Capric Triglyceride, Propanediol, Glycerin, Sodium Acrylates Copolymer, Citrus Junos Seed Oil, Panthenol, Ascorbyl Glucoside, Hylocereus Undatus Fruit Extract, Ilex Guayusa Leaf Extract, Ilex Paraguariensis Leaf Extract, Jania Rubens Extract, Lactobacillus Ferment, Maltodextrin, Malus Domestica Fruit Cell Culture Extract, Momordica Cochinchinensis Seed Extract, Punica Granatum Seed Extract, Sodium Carrageenan, Adenosine, Biotin, Caffeine, Caprylyl Glycol, Chrysin, Dipeptide-2, Hesperidin Methyl Chalcone, Hydroxyacetophenone, N-Hydroxysuccinimide, Palmitoyl Tetrapeptide-7, Palmitoyl Tripeptide-1, Sodium Hyaluronate, Sodium Hydroxide, 1,2-Hexanediol, Niacinamide, Tocopherol, Alcohol, Cellulose, CI 77891, Citric Acid, Ethylhexylglycerin, Hydroxyethylcellulose, Lecithin, Sodium Acetate, Sodium Citrate, Steareth-20, Synthetic Fluorphlogopite, Tin Oxide, Xanthan Gum, Chlorhexidine Digluconate, Phenoxyethanol, Potassium Sorbate, Sodium Benzoate

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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.

Adenosine is a purine nucleoside that your body already makes in every cell. In skincare, it acts mainly as a skin conditioning and anti-aging agent.

The way it works is fairly well mapped out:

Your skin has cells called fibroblasts that build collagen (the stuff that keeps skin firm and smooth). Adenosine basically flips a switch on these cells that tells them to get to work making more collagen and other proteins. These cells slow down on their own as skin ages, so Adenosine helps give them a little nudge to keep going.

The clinical backing is pretty solid too.

A blind, randomized, placebo-controlled trial of 126 women aged 45-65 tested a 0.1% cream twice daily and found real improvements in crow's feet and frown lines using a precise 3D skin-mapping technique; these changes showed up by week 3 and held at 2 months.

A later study using Adenosine-loaded dissolving microneedle patches reported gains in wrinkle depth, dermal density, elasticity, and hydration.

On concentrations, South Korea's Ministry of Food and Drug Safety has set 0.04% as the approved functional anti-wrinkle level. You'll typically see this ingredient used somewhere in the 0.04-0.1% range since it works at low doses.

This ingredient has been found safe for cosmetics with the data showing no irritation or sensitization.

Overall, this is a great ingredient for any anti-aging routine and has no photosensitizing effect, so it suits both AM and PM use.

Biotin is a B vitamin that is naturally produced by our bodies. It is also called Vitamin H.

Our bodies use biotin in the metabolism process. It also helps our bodies use enzymes and move nutrients around. A biotin deficiency can lead to brittle hair and nails.

More research is needed on applying biotin topically. However, taking biotin orally has been shown to help nourish the skin, hair, and nails. They play a role in forming skin-hydrating fatty acids.

Biotin is water-soluble. It can be found in foods such as fish, eggs, dairy, nuts, and meat. Vitamin H stands for "haar" and "haut". These are the German words for hair and skin.

Chlorhexidine Digluconate is a preservative. It can worsen eczema.

We don't have a description for Chrysin yet.

Ci 77891 is a white pigment from Titanium dioxide. It is naturally found in minerals such as rutile and ilmenite.

It's main function is to add a white color to cosmetics. It can also be mixed with other colors to create different shades.

Ci 77891 is commonly found in sunscreens due to its ability to block UV rays.

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.

We don't have a description for N-Hydroxysuccinimide yet.

Palmitoyl Tetrapeptide-7 (formerly Palmitoyl Tetrapeptide-3) is a synthetic peptide. Its main job is to fight what researchers call "inflammaging".

"Inflammaging" is the slow, low-grade chronic inflammation that quietly breaks down collagen as we age.

This ingredient calms down a specific inflammation signal in your skin cells (called IL-6). When left unchecked, this signal triggers enzymes that break down collagen and elastin.

Clinical testing showed statistically significant improvements in:

Studies also found the more of this ingredient used, the more your skin produces Collagen I, fibronectin, and hyaluronic acid.

You'll likely see this ingredient paired with Palmitoyl Tripeptide-1 in the well-known Matrixyl 3000 complex for enhanced anti-aging effects.

A 3% concentration applied twice daily for two months showed meaningful skin rejuvenation results in clinical panels.

Fungal acne note: Usually a palmitic acid component can feed Malassezia in unbound form, but here is is covalently bonded to the peptide. This means it is very difficult for Malassezia to access, and therefore very unlikely to cause fungal acne.

Palmitoyl Tripeptide-1 (aka Pal-GHK) is a synthetic signal peptide made of three amino acids attached to palmitic acid.

That fatty acid attachment is the key: it boosts the peptide's ability to penetrate the skin barrier. This puts it closer to the dermal cells where it can actually make a difference.

Once there, it acts as a matrikine, a signaling peptide that prompts fibroblasts to produce more collagen, fibronectin, and hyaluronic acid.

In vitro studies show it can boost collagen production in skin cells even when UV-damaged skin samples were treated with it at a tiny concentration (it almost fully restored dermal collagen at 5ppm). It achieved this at 100x lower concentration than retinoic acid, which needed 500 ppm to do the same thing.

Human clinical data is promising, but modest:

A study of 23 female volunteers found a small but statistically significant increase (~4%) in skin thickness after treatment at 4 ppm.

A separate small trial of 15 women showed statistically significant reductions in wrinkle length, depth, and skin roughness after applying it twice daily for four weeks.

You'll likely see Pal-GHK paired with Palmitoyl Tetrapeptide-7 as part of the Matrixyl 3000 complex.

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.

Steareth-20 is an emulsifier and solubilizer. It is created from stearyl alcohol with ~20 units of ethylene oxide to give it a strong preference for water.

As an emulsifier, it helps oil-in-water emulsions like lotions, creams, and cleansers stay stable. It also solubilizes small amounts of oil-loving ingredients (like fragrance) into water-based formulas.

You'll likely find this ingredient with steareth-2 (it's oil-loving sister) where the two work together to give products a cushiony feel.

Typical use levels sit at around 1-5% and this ingredient has been found to be non-irritating by the CIR Expert Panel.

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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