Allies of Skin 20% Vitamin C Brighten + Firm Serum Versus Paula's Choice Resist Super Antioxidant Serum

Allies of Skin 20% Vitamin C Brighten + Firm Serum Versus Paula's Choice Resist Super Antioxidant Serum

This brightening serum is formulated around 3-O-Ethyl Ascorbic Acid and Glutathione to brighten dull-looking skin.

This anti-aging serum is formulated around Tetrahexyldecyl Ascorbate and Palmitoyl Tripeptide-5 to soften the look of wrinkles and brighten dull-looking skin.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Propanediol

Glycerin

3-O-Ethyl Ascorbic Acid

Benzimidazole Diamond Amidoethyl Urea Carbamoyl Propyl Polymethylsilsesquioxane

Dimethyl Isosorbide

Helianthus Annuus Seed Wax

Polyglyceryl-10 Tristearate

Ethoxydiglycol

Dicaprylyl Ether

Water

Caprylyl Glycol

Citrus Aurantium Dulcis Callus Culture Extract

Glutathione

Acetyl Cysteine

Dimethylmethoxy Chromanol

Ergothioneine

Tocopherol

Gluconolactone

Leuconostoc/Radish Root Ferment Filtrate

Xanthan Gum

Silica

Sodium Benzoate

Calcium Gluconate

Phenoxyethanol

Propanediol, Glycerin, 3-O-Ethyl Ascorbic Acid, Benzimidazole Diamond Amidoethyl Urea Carbamoyl Propyl Polymethylsilsesquioxane, Dimethyl Isosorbide, Helianthus Annuus Seed Wax, Polyglyceryl-10 Tristearate, Ethoxydiglycol, Dicaprylyl Ether, Water, Caprylyl Glycol, Citrus Aurantium Dulcis Callus Culture Extract, Glutathione, Acetyl Cysteine, Dimethylmethoxy Chromanol, Ergothioneine, Tocopherol, Gluconolactone, Leuconostoc/Radish Root Ferment Filtrate, Xanthan Gum, Silica, Sodium Benzoate, Calcium Gluconate, Phenoxyethanol

Cyclopentasiloxane

Dimethicone

Tetrahexyldecyl Ascorbate

Palmitoyl Tripeptide-5

Ceramide NP

Tocotrienols

Ubiquinone

Thioctic Acid

Tocopheryl Acetate

Magnesium Ascorbyl Phosphate

Ferulic Acid

Beta-Glucan

Superoxide Dismutase

Epigallocatechin Gallate

Xanthophylls

Glycine Soja Seed Extract

Arctostaphylos Uva Ursi Leaf Extract

Lupinus Albus Seed Extract

Curcuma Longa Root

Elaeis Guineensis Oil

Cyclopentasiloxane, Dimethicone, Tetrahexyldecyl Ascorbate, Palmitoyl Tripeptide-5, Ceramide NP, Tocotrienols, Tocopherol, Ubiquinone, Thioctic Acid, Tocopheryl Acetate, Magnesium Ascorbyl Phosphate, Ferulic Acid, Beta-Glucan, Superoxide Dismutase, Epigallocatechin Gallate, Ergothioneine, Glutathione, Xanthophylls, Glycine Soja Seed Extract, Glycerin, Arctostaphylos Uva Ursi Leaf Extract, Lupinus Albus Seed Extract, Curcuma Longa Root, Elaeis Guineensis Oil, Phenoxyethanol

Reviews

Alternatives

Ingredients Explained

These ingredients are found in both products.

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

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

Glutathione is a tiny protein-like molecule (a "tripeptide" build from 3 amino acids: glycine, cysteine, and glutamic acid) that your body already makes on its own.

Inside your body, it acts as one of the skin's main antioxidants that help fight against free radicals.

In skincare, it's best known as a brightening ingredient that slows down tyrosinase, the key enzyme that makes skin pigment. It also nudges the skin toward making a lighter type of pigment instead of a darker one.

This is why you'll see it in products aimed at dark spots and uneven tone.

A small number of real human trials have found a topical glutathione lotion:

The honest caveat is that the current evidence is still thin (few studies, small groups, short timelines). Glutathione also doesn't absorb into skin very easily so results tend to be modest and fade if you stop using it.

One thing worth clearing up:

The scary side effects you may have heard about come from glutathione injected intravenously, which has real safety concerns. Applying it topically is a completely different thing and has a clean track record.

Most human studies used it around 2% (as Glutathione or Glutathione Disulfide) and a 2% oxidized glutathione lotion and a 2% S-acyl glutathione cream are the concentrations with actual clinical data behind them.

There's no established "ideal" percentage yet but 1-2% is the evidence-backed range.

Allergy-wise, there is very low risk for this ingredient; it was well-tolerated across the topical trials. Only one participant had mild temporary redness that cleared up on its own and another study reported no adverse reactions at all.

One trial had ~10% of users drop out for irritation was using a combination cream that also had 10% azelaic acid so the irritation likely wasn't from the glutathione. There's no notable contact-allergy signal for topical glutathione in the literature but patch-testing before first use is still sensible for those with sensitive skin.

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.

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.

Similar Comparisons