Paula's Choice C15 Super Booster Versus Kiehl's Vital Skin-Strengthening Hyaluronic Acid Super Serum

Paula's Choice C15 Super Booster Versus Kiehl's Vital Skin-Strengthening Hyaluronic Acid Super Serum

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

This hydrating serum is formulated around Schisandra Chinensis Fruit Extract and Panax Ginseng Root Extract to hydrate skin.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Ascorbic Acid

Dipropylene Glycol

Propanediol

Glycerin

Ethoxydiglycol

Sodium Hydroxide

PPG-26-Buteth-26

PEG-40 Hydrogenated Castor Oil

Bisabolol

Ferulic Acid

Sodium Phytate

Decylene Glycol

Tocopherol

1,2-Hexanediol

Sphingomonas Ferment Extract

Phenoxyethanol

Water, Ascorbic Acid, Dipropylene Glycol, Propanediol, Glycerin, Ethoxydiglycol, Sodium Hydroxide, PPG-26-Buteth-26, PEG-40 Hydrogenated Castor Oil, Bisabolol, Ferulic Acid, Sodium Phytate, Decylene Glycol, Tocopherol, 1,2-Hexanediol, Sphingomonas Ferment Extract, Phenoxyethanol

Dimethicone

Alcohol Denat.

Hamamelis Virginiana Water

Ammonium Polyacryloyldimethyl Taurate

Schisandra Chinensis Fruit Extract

Capryloyl Salicylic Acid

Caprylyl Glycol

Xanthan Gum

PEG-60 Hydrogenated Castor Oil

Panax Ginseng Root Extract

Sodium Acetylated Hyaluronate

PEG-20 Methyl Glucose Sesquistearate

Disodium EDTA

Ocimum Sanctum Leaf Extract

Citrus Aurantium Dulcis Peel Oil

Limonene

Adenosine

Methyldihydrojasmonate

Citric Acid

Eugenol

Sodium Benzoate

Pelargonium Graveolens Flower Oil

Citral

Potassium Sorbate

Lavandula Angustifolia Oil

Cymbopogon Schoenanthus Oil

Citronellol

Linalool

Geraniol

Rosmarinus Officinalis Leaf Oil

Water, Dimethicone, Glycerin, Alcohol Denat., Hamamelis Virginiana Water, Propanediol, Phenoxyethanol, Tocopherol, Ammonium Polyacryloyldimethyl Taurate, Schisandra Chinensis Fruit Extract, Capryloyl Salicylic Acid, Caprylyl Glycol, Xanthan Gum, PEG-60 Hydrogenated Castor Oil, Panax Ginseng Root Extract, Sodium Acetylated Hyaluronate, PEG-20 Methyl Glucose Sesquistearate, Disodium EDTA, Ocimum Sanctum Leaf Extract, Citrus Aurantium Dulcis Peel Oil, Limonene, Adenosine, Sodium Hydroxide, Methyldihydrojasmonate, Citric Acid, Eugenol, Sodium Benzoate, Pelargonium Graveolens Flower Oil, Citral, Potassium Sorbate, Lavandula Angustifolia Oil, Cymbopogon Schoenanthus Oil, Citronellol, Linalool, Geraniol, Rosmarinus Officinalis Leaf Oil

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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.

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.

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.

Propanediol is an all-star ingredient. It softens, hydrates, and smooths the skin.

It’s often used to:

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.

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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