Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

Paula's Choice Resist Intensive Repair Cream Versus La Roche-Posay Redermic R Intensive Anti-Aging Treatment

Paula's Choice Resist Intensive Repair Cream Versus La Roche-Posay Redermic R Intensive Anti-Aging Treatment This anti-aging moisturizer is formulated around Retinol and Simmondsia Chinensis Seed Oil to soften the look of wrinkles and hydrate skin. This anti-a

Paula's Choice Resist Intensive Repair Cream Versus La Roche-Posay Redermic R Intensive Anti-Aging Treatment

This anti-aging moisturizer is formulated around Retinol and Simmondsia Chinensis Seed Oil to soften the look of wrinkles and hydrate skin.

This anti-aging treatment is formulated around Retinol and Retinyl Linoleate to soften the look of wrinkles and refine skin texture.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Ethylhexyl Stearate

Simmondsia Chinensis Seed Oil

Butylene Glycol

Glycerin

Caprylic/Capric Triglyceride

Petrolatum

Cetearyl Alcohol

Dimethicone

Dipentaerythrityl Hexacaprylate/Hexacaprate

Glyceryl Stearate

Tridecyl Trimellitate

PEG-100 Stearate

Phenyl Trimethicone

Retinol

Adenosine

Palmitoyl Tetrapeptide-7

Palmitoyl Hexapeptide-12

Palmitoyl Tripeptide-1

Ceramide Ng

Sodium Hyaluronate

Magnesium Ascorbyl Phosphate

Niacinamide

Tocopherol

Lecithin

Linoleic Acid

Linolenic Acid

Retinyl Palmitate

Glycyrrhiza Glabra Root Extract

Camellia Oleifera Leaf Extract

Citrullus Lanatus Fruit Extract

Lens Esculenta Fruit Extract

Pyrus Malus Fruit Extract

Glycine Soja Sterols

Tribehenin

PEG-10 Phytosterol

Magnesium Aluminum Silicate

Sodium PCA

Sodium Lactate

Pullulan

Xanthan Gum

Sodium Hydroxide

Neopentyl Glycol Dicaprylate/Dicaprate

Cetearyl Glucoside

Tridecyl Stearate

Behenyl Alcohol

Sclerotium Gum

Carbomer

C12-15 Alkyl Benzoate

Polysorbate 20

Disodium EDTA

Sorbic Acid

Phenoxyethanol

Chlorphenesin

Benzoic Acid

Water, Ethylhexyl Stearate, Simmondsia Chinensis Seed Oil, Butylene Glycol, Glycerin, Caprylic/Capric Triglyceride, Petrolatum, Cetearyl Alcohol, Dimethicone, Dipentaerythrityl Hexacaprylate/Hexacaprate, Glyceryl Stearate, Tridecyl Trimellitate, PEG-100 Stearate, Phenyl Trimethicone, Retinol, Adenosine, Palmitoyl Tetrapeptide-7, Palmitoyl Hexapeptide-12, Palmitoyl Tripeptide-1, Ceramide Ng, Sodium Hyaluronate, Magnesium Ascorbyl Phosphate, Niacinamide, Tocopherol, Lecithin, Linoleic Acid, Linolenic Acid, Retinyl Palmitate, Glycyrrhiza Glabra Root Extract, Camellia Oleifera Leaf Extract, Citrullus Lanatus Fruit Extract, Lens Esculenta Fruit Extract, Pyrus Malus Fruit Extract, Glycine Soja Sterols, Tribehenin, PEG-10 Phytosterol, Magnesium Aluminum Silicate, Sodium PCA, Sodium Lactate, Pullulan, Xanthan Gum, Sodium Hydroxide, Neopentyl Glycol Dicaprylate/Dicaprate, Cetearyl Glucoside, Tridecyl Stearate, Behenyl Alcohol, Sclerotium Gum, Carbomer, C12-15 Alkyl Benzoate, Polysorbate 20, Disodium EDTA, Sorbic Acid, Phenoxyethanol, Chlorphenesin, Benzoic Acid

Isostearyl Neopentanoate

Octyldodecanol

Propylene Glycol

Pentylene Glycol

Acrylamide

Sodium

Ammonium Acryloyldimethyltaurate/Vp Copolymer

Vp/Va Copolymer

Glycine Soja Oil

Triethanolamine

Isohexadecane

Retinyl Linoleate

Capryloyl Salicylic Acid

Caprylyl Glycol

Polysorbate 80

Parfum

Water, Isostearyl Neopentanoate, Glycerin, Octyldodecanol, Propylene Glycol, Pentylene Glycol, Acrylamide, Sodium, Ammonium Acryloyldimethyltaurate/Vp Copolymer, Vp/Va Copolymer, Cetearyl Alcohol, Glycine Soja Oil, Triethanolamine, Isohexadecane, Sodium Hyaluronate, Retinol, Retinyl Linoleate, Adenosine, Capryloyl Salicylic Acid, Caprylyl Glycol, Polysorbate 80, Phenoxyethanol, Parfum

Reviews

Be the first to review

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.

Cetearyl alcohol is a waxy mixture of two fatty alcohols: cetyl alcohol and stearyl alcohol. It is an emollient and emulsifier.

Despite having "alcohol" in its name, it has nothing to do with drying solvent alcohols; the FDA also allows "alcohol-free" products to contain fatty alcohols like this ingredient.

It plays several roles in a formula:

Typical use levels for this ingredient sit around 1-10% and the Cosmetic Ingredient Review Expert Panel has affirmed safety at concentrations up to 25% in leave-on products.

Multiple assessments have found it to be non-irritating and non-sensitizing to most people.

However, there have been some cases of allergic contact dermatitis in patients with chronically compromised skin barriers.

Cetearyl alcohol has a comedogenic rating of 2 and irritancy rating of 1. Both of these numbers come from the 1989 study that used rabbit ears; a "2" means mildly comedogenic and a "1" means low irritancy.

Here's the catch: rabbit skin is more sensitive than human skin and throws a lot of false positives. A 1996 reappraisal found that ingredients rated 1-2 in the rabbit ear tests are generally safe for humans.

Remember comedogenic ratings are unable to assess the entire formula of a product or how it will react on your skin. Just be sure to patch test if you are unsure about certain ingredients.

This ingredient is not fungal acne safe. Cetearyl alcohol is a fatty alcohol with chain lengths that fall within the range that Malassezia can metabolize.

A 2019 study has also observed Malassezia growth in the presence of this ingredient, confirming it to be not-fungal acne safe.

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.

Retinol is one of the most studied anti-aging ingredients in skincare (and for good reason!).

It's a form of vitamin A that your skin converts into Retinoic Acid, the active molecule that actually does the work in your cells.

That conversion happens in two steps: your skin first turns Retinol into Retinaldehyde (also called Retinal), then turns Retinaldehyde into Retinoic Acid.

Retinol is converted to biologically active retinoic acid via retinaldehyde by dehydrogenases in a two-step oxidation process.

Each step is a little "upgrade" toward the active form which is part of why Retinol is gentler than prescription Retinoic Acid; your skin does the work gradually. This also explains where Retinol sits in the retinoid family.

Here is the retinoid family ranked roughly by strength: Retinyl Esters (like Retinyl Palmitate) < Retinol < Retinaldehyde < Retinoic Acid.

Retinoid activity increases in that order, while tolerance runs in reverse; retinyl esters are the gentlest and retinoic acid the most irritating.

The more conversion steps an ingredient needs, the gentler (and slower) it tends to be, so Retinol lands in a nice middle spot. It's more effective than the esters, gentler than prescription options.

Once it becomes Retinoic Acid, it binds to receptors inside your cells' nuclei (called RARs and RXRs). These receptor pairs bind to specific DNA motifs called retinoic acid response elements and act like switches that turn certain genes on or off.

In practice, this means a few things happen in a formula. It:

That last two are worth a closer look.

A study that tested Retinol directly (not just prescription Retinoic Acid) found that four weeks of retinol thickened the epidermis and switched on the genes for Collagen I and Collagen III, with more procollagen I and III showing up in the skin. And after twelve weeks, facial wrinkles were visibly reduced.

Retinoids more broadly stimulate the skin's synthesis of hyaluronan and other glycosaminoglycans, part of what gives skin a plumper, more hydrated look over time.

So even the gentler OTC form is doing real structural work (not just sitting on the surface).

It's also worth knowing Retinol isn't only a wrinkle ingredient; it can help with uneven tone, dark spots, rough texture, and the look of pores as well because it speeds up turnover and influences pigment.

The research backs this up as well.

A pooled analysis of six clinical studies found that 0.1% stabilized retinol improved all signs of photoaging versus vehicle as early as week 4 and through 12 weeks, with only a few mild cases of irritation.

Another study comparing concentrations found that 0.3% and 1% Retinol were similarly effective at remodeling photodamaged skin, but 0.3% caused fewer adverse reactions when used daily (a useful reminder that more isn't always better).

Retinol is about tenfold less potent than Retinoic Acid. This is why it works as a gentler, non-prescription option that builds results over time.

Typical concentrations range from 0.1-1%, with 0.1% to 0.3% being a well-supported sweet spot for visible benefits with good tolerability.

One quirk worth mentioning: Retinol is famously unstable.

It's highly sensitive to light and oxygen, and UV exposure breaks it down into a range of degradation products.

Real-world testing bears this out, with retinoid content in some products dropping anywhere from 0% to 80% after six months at room temperature, and even more at higher temperatures.

This is why good formulations lean on opaque, air-tight packaging (think tubes and pumps, not clear jars) and often "encapsulate" the Retinol to shield it.

Signs of oxidation include your product turning yellow or smelling "off". Keeping it somewhere cool and dark, and using it up within a few months of opening helps it stay effective.

The most common side effects are mild and temporary: usually some dryness, redness, or light peeling as your skin adjusts. These tend to settle with consistent and lower-frequency use.

Like all retinoids, Retinol works best with nightly use, a good moisturizer, and daytime sunscreen.

The "ramp up" method works well: start with Retinol once a week to give your skin time to adjust, which keeps irritation low. Slowly add more nights until you reach your goal frequency once your skin feels comfortable.

Retinoids also make your skin more sensitive to the sun in the first few weeks, so wear sunscreen every morning and protect your skin from direct sun while you build up tolerance.

One safety note: topical Retinoids aren't recommended during pregnancy or breastfeeding. Systemic absorption from creams is low but because high oral vitamin A is a known teratogen and topical safety data are limited, most clinicians recommend stopping retinoids when pregnant or trying to conceive.

Sodium Hyaluronate is the salt form of hyaluronic acid. It is a long sugar chain that is naturally found in your skin, joints, and connective tissue that maintains hydration and elasticity.

In skincare, it works as a humectant. It pulls water from the environment and deeper layers of skin and binds it to the surface.

Interestingly, the size of the molecule affects its behavior:

Some clinical evidence links low molecular weight versions to improved wrinkle depth, elasticity, anti-inflammatory effects, and barrier repair.

Many serums use a blend of both weights so you can get surface hydration plus longer-lasting and deeper effects.

You'll typically see concentrations between 0.1-2% for this ingredient.

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!

Similar Comparisons

The reference edit

Ingredients, questions
& further reading.

Connected source records selected through this article’s public topic index.

01

Formula cabinet

Ingredients & structured notes

Ingredient index

Ingredients Explained

  1. 01These ingredients are found in both products.
  2. 02Ingredients higher up in an ingredient list are typically present in a larger amount.
  3. 03Water. 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.
  4. 04So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.
  5. 05You'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!
Source · skinsort.com
02

Product index

Related product references

03

Comparison edit

Read side by side