Paula's Choice C5 Super Boost Moisturizer Versus Kiehl's Ultra Facial Moisturizer

Paula's Choice C5 Super Boost Moisturizer Versus Kiehl's Ultra Facial Moisturizer

This brightening moisturizer is formulated around 3-O-Ethyl Ascorbic Acid and Ascorbyl Glucoside to brighten dull-looking skin.

This day moisturizer is formulated around Squalene to hydrate skin.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Dicaprylyl Carbonate

3-O-Ethyl Ascorbic Acid

Dimethicone

Butylene Glycol

Polyglyceryl-6 Distearate

Ascorbyl Glucoside

Squalane

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Acetyl Sh-Hexapeptide-5 Amide Acetate

Citrullus Lanatus Seed Oil

Hydrogenated Lecithin

Theobroma Cacao Seed Butter

Hydrogenated Phosphatidylcholine

Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate

Sodium Hyaluronate

Oryza Sativa Bran Extract

Propanediol

Jojoba Esters

Tocopherol

Acetyl Zingerone

Cetyl Palmitate

Caprylyl Glycol

Cetyl Alcohol

Polyglyceryl-3 Beeswax

Sodium Hydroxide

Sorbitan Olivate

Sorbitan Palmitate

Helianthus Annuus Extract

Ethylhexylglycerin

Hexylene Glycol

Sodium Phytate

Polysorbate 60

Sorbitan Isostearate

Lecithin

Rosmarinus Officinalis Leaf Extract

Glycine Soja Oil

Lysolecithin

Bacillus Ferment

Citric Acid

Polyglutamic Acid

Beta-Sitosterol

Phytic Acid

Squalene

Phenoxyethanol

Sodium Benzoate

Potassium Sorbate

Water, Dicaprylyl Carbonate, 3-O-Ethyl Ascorbic Acid, Dimethicone, Butylene Glycol, Polyglyceryl-6 Distearate, Ascorbyl Glucoside, Squalane, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Acetyl Sh-Hexapeptide-5 Amide Acetate, Citrullus Lanatus Seed Oil, Hydrogenated Lecithin, Theobroma Cacao Seed Butter, Hydrogenated Phosphatidylcholine, Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate, Sodium Hyaluronate, Oryza Sativa Bran Extract, Propanediol, Jojoba Esters, Tocopherol, Acetyl Zingerone, Cetyl Palmitate, Caprylyl Glycol, Cetyl Alcohol, Polyglyceryl-3 Beeswax, Sodium Hydroxide, Sorbitan Olivate, Sorbitan Palmitate, Helianthus Annuus Extract, Ethylhexylglycerin, Hexylene Glycol, Sodium Phytate, Polysorbate 60, Sorbitan Isostearate, Lecithin, Rosmarinus Officinalis Leaf Extract, Glycine Soja Oil, Lysolecithin, Bacillus Ferment, Citric Acid, Polyglutamic Acid, Beta-Sitosterol, Phytic Acid, Squalene, Phenoxyethanol, Sodium Benzoate, Potassium Sorbate

Propylene Glycol

Dicaprylyl Ether

Glycerin

PEG-100 Stearate

Glyceryl Stearate

Hydrogenated Polyisobutene

Sorbitan Oleate

Acrylates/C10-30 Alkyl Acrylate Crosspolymer

Triethanolamine

Beeswax

Disodium EDTA

Stearic Acid

Myristyl Alcohol

Prunus Amygdalus Dulcis Oil

Prunus Armeniaca Kernel Oil

Persea Gratissima Oil

Water, Propylene Glycol, Dicaprylyl Ether, Glycerin, PEG-100 Stearate, Glyceryl Stearate, Squalene, Hydrogenated Polyisobutene, Phenoxyethanol, Sorbitan Oleate, Caprylyl Glycol, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Triethanolamine, Beeswax, Tocopherol, Disodium EDTA, Stearic Acid, Myristyl Alcohol, Prunus Amygdalus Dulcis Oil, Prunus Armeniaca Kernel Oil, Persea Gratissima 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.

Caprylyl Glycol is a humectant, skin conditioner, emollient, and preservative booster derived from either caprylic acid or synthetically created.

Typical use levels vary from 0.3-1% as a preservative booster and go up to 2% to condition skin.

Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).

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.

Squalene is one of the main components of skin surface lipids. It is naturally found in our skin and makes up about 13% of sebum.

Topically, it is an emollient and skin conditioning agent.

Research highlights its role in antioxidant activity, anti-inflammatory effects, skin barrier protection, and wound healing support.

In vivo research has shown that transepidermal water loss (TEWL) caused by irritant exposure can be reverse with squalene supplementation (pointing to barrier recovery support).

Its antioxidant activity is backed by ex vivo and cell-based evidence showing it can scavenge free radicals but large-scale human clinical trials isolating this effect remain limited.

One study found squalene regulated proinflammatory behavior in ways relevant to wound healing, and in vitro fibroblast studies also shows it stimulates cell migration which is a key step in skin repair.

There's just one nuance to know about this ingredient:

Squalene is particularly vulnerable to oxidation; it breaks down from UV exposure 10x faster than the other lipids on your skin's surface. The byproducts of that breakdown can clog pores and trigger inflammation, potentially worsening acne.

This is why squalene is often hydrogenated into its stable counterpart: squalane (with an "a"). Most great formulations will have alreadu kept this in mind.

Squalene has shown no significant clinical evidence of sensitization and is a great hydrating ingredient.

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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