Paula's Choice 25% Vitamin C + Glutathione Clinical Serum Versus SkinBetter Science Alto Defense Serum

Paula's Choice 25% Vitamin C + Glutathione Clinical Serum Versus SkinBetter Science Alto Defense Serum

This brightening serum is formulated around Tetrahexyldecyl Ascorbate and Ascorbyl Glucoside to brighten dull-looking skin and fade the look of dark spots.

This calming serum is formulated around Glycyrrhiza Glabra Root Extract and Tetrahexyldecyl Ascorbate to calm redness and brighten dull-looking skin.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Tetrahexyldecyl Ascorbate

Dimethicone

Glycerin

C9-12 Alkane

Ascorbyl Glucoside

Silica

Pyrus Malus Fruit Extract

Hydrogenated Lecithin

Polyglyceryl-6 Polyricinoleate

Acrylates/C10-30 Alkyl Acrylate Crosspolymer

Xanthan Gum

Oryza Sativa Bran Extract

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Cetyl Alcohol

Caprylyl Glycol

Lysine Carboxymethyl Cysteinate

Coco-Caprylate/Caprate

Tocopherol

Glutathione

Sodium Citrate

Sodium Phytate

Hexylene Glycol

Ethylhexylglycerin

Helianthus Annuus Seed Extract

Urea

Mannitol

Caprylic/Capric Triglyceride

Sodium PCA

Rosmarinus Officinalis Leaf Extract

Polysorbate 60

Sorbitan Isostearate

Trehalose

Ascorbic Acid

Glucose

Vanilla Planifolia Fruit Extract

Polyquaternium-51

Ergothioneine

Triacetin

Sodium Hyaluronate

Phenoxyethanol

Water, Tetrahexyldecyl Ascorbate, Dimethicone, Glycerin, C9-12 Alkane, Ascorbyl Glucoside, Silica, Pyrus Malus Fruit Extract, Hydrogenated Lecithin, Polyglyceryl-6 Polyricinoleate, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Xanthan Gum, Oryza Sativa Bran Extract, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Cetyl Alcohol, Caprylyl Glycol, Lysine Carboxymethyl Cysteinate, Coco-Caprylate/Caprate, Tocopherol, Glutathione, Sodium Citrate, Sodium Phytate, Hexylene Glycol, Ethylhexylglycerin, Helianthus Annuus Seed Extract, Urea, Mannitol, Caprylic/Capric Triglyceride, Sodium PCA, Rosmarinus Officinalis Leaf Extract, Polysorbate 60, Sorbitan Isostearate, Trehalose, Ascorbic Acid, Glucose, Vanilla Planifolia Fruit Extract, Polyquaternium-51, Ergothioneine, Triacetin, Sodium Hyaluronate, Phenoxyethanol

Butylene Glycol

Propanediol

Ethylhexyl Olivate

Cetearyl Alcohol

Chlorogenic Acids

Hydrolyzed Sodium Hyaluronate

Lauryl Lactate

Dimethyl Isosorbide

Glycyrrhiza Glabra Root Extract

Benzylidene Dimethoxydimethylindanone

Arabidopsis Thaliana Extract

Carnosine

Camellia Sinensis Leaf Extract

Vitis Vinifera Seed Extract

Theobroma Cacao Seed Extract

Curcuma Longa Root Extract

Olea Europaea Fruit Extract

Euterpe Oleracea Fruit Extract

Trifluoroacetyl Tripeptide-2

Buddleja Officinalis Flower Extract

Coffea Arabica Leaf Cell Extract

Crocus Sativus Leaf Cell Culture Extract

Superoxide Dismutase

Ubiquinone

Zingiber Officinale Root Extract

Ceramide NP

Ceramide AP

Ceramide EOP

Linoleic Acid

Linolenic Acid

Sea Whip Extract

Bisabolol

Tocopheryl Acetate

Cholesterol

Phytosphingosine

Jojoba Esters

Pentylene Glycol

Methyl Gluceth-20

Helianthus Annuus Seed Wax

Acacia Decurrens Flower Wax

Lecithin

Sodium Lauroyl Lactylate

Dicetyl Phosphate

Propanediol Dicaprylate/Caprate

Polyglycerin-3

Ceteth-20 Phosphate

Diisostearyl Malate

Steareth-2

Acacia Senegal Gum

Carbomer

Dextran

Sodium Hydroxide

Citric Acid

Disodium EDTA

Water, Butylene Glycol, Propanediol, Ethylhexyl Olivate, Cetearyl Alcohol, Chlorogenic Acids, Hydrolyzed Sodium Hyaluronate, Lauryl Lactate, Dimethyl Isosorbide, Glycyrrhiza Glabra Root Extract, Tetrahexyldecyl Ascorbate, Ergothioneine, Benzylidene Dimethoxydimethylindanone, Arabidopsis Thaliana Extract, Carnosine, Camellia Sinensis Leaf Extract, Vitis Vinifera Seed Extract, Theobroma Cacao Seed Extract, Curcuma Longa Root Extract, Olea Europaea Fruit Extract, Euterpe Oleracea Fruit Extract, Trifluoroacetyl Tripeptide-2, Buddleja Officinalis Flower Extract, Coffea Arabica Leaf Cell Extract, Crocus Sativus Leaf Cell Culture Extract, Superoxide Dismutase, Ubiquinone, Zingiber Officinale Root Extract, Ceramide NP, Ceramide AP, Ceramide EOP, Linoleic Acid, Linolenic Acid, Sea Whip Extract, Bisabolol, Tocopherol, Tocopheryl Acetate, Cholesterol, Phytosphingosine, Jojoba Esters, Sodium PCA, Pentylene Glycol, Methyl Gluceth-20, Glycerin, Helianthus Annuus Seed Wax, Acacia Decurrens Flower Wax, Lecithin, Sodium Lauroyl Lactylate, Dicetyl Phosphate, Propanediol Dicaprylate/Caprate, Polyglycerin-3, Ceteth-20 Phosphate, Diisostearyl Malate, Xanthan Gum, Steareth-2, Acacia Senegal Gum, Carbomer, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Dextran, Sodium Hydroxide, Citric Acid, Disodium EDTA, Ethylhexylglycerin, Phenoxyethanol

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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.

Ergothioneine is an amino acid found naturally in mushrooms, grains, and meat. It has antioxidant and skin soothing properties.

This amino acid helps with:

Maintaining DNA stability and cell reproduction

Enhances cellular immunity

Skin brightening

Anti-aging

Skin soothing

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.

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 PCA (the salt of PCA) is one of the most well-established humectants in skincare.

Why is it so special? Your skin already makes it naturally; it's a natural component of your skin's Natural Moisturizing Factor (NMF), or the mix of water-binding compounds inside your skin cells that keeps things soft and hydrated.

As a cosmetic ingredient, it grabs water and holds it in the upper layers of skin to smooth roughness and ease dehydration.

There's some clinical support for the NMF approach with a study showing that a cream built to mimic the skin's NMF significantly boosted hydration.

Safety-wise, this ingredient non-irritating, non-comedogenic, and non-phototoxic in testing, with minimal skin absorption.

It also works really well with other hydrators like glycerin or hyaluronic acid, and typical usage is somewhere between 0.2-4%.

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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