Skin science article
Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Elizabeth Arden Ceramide Retinol + HPR Rapid Skin Renewing Water Cream
Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Elizabeth Arden Ceramide Retinol + HPR Rapid Skin Renewing Water Cream This anti-aging serum is formulated around Niacinamide and Ceramide NP to soften the look of wrinkles and refin
Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Elizabeth Arden Ceramide Retinol + HPR Rapid Skin Renewing Water Cream
This anti-aging serum is formulated around Niacinamide and Ceramide NP to soften the look of wrinkles and refine skin texture.
This anti-aging moisturizer is formulated around Ceramide NP and Hydroxypinacolone Retinoate to soften the look of wrinkles and refine skin texture.
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Water
Glycerin
Butylene Glycol
Pentylene Glycol
Niacinamide
Cetyl Alcohol
Isohexadecane
Isononyl Isononanoate
Diisopropyl Sebacate
2-Oleamido-1,3-Octadecanediol
4-T-Butylcyclohexanol
Acetyl Dipeptide-1 Cetyl Ester
Adenosine
Ceramide NP
Hydroxypalmitoyl Sphinganine
Lauroyl Lysine
Octyldodecanol
Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate
Sodium Chloride
Sodium Hyaluronate
Sodium Hydroxide
Trisodium Ethylenediamine Disuccinate
Retinol
Tocopherol
Dicaprylyl Ether
Ammonium Polyacryloyldimethyl Taurate
Behenyl Alcohol
Caprylyl Glycol
Carbomer
Cetearyl Alcohol
Cetearyl Glucoside
Glycine Soja Oil
Helianthus Annuus Seed Oil
Hydroxyethylcellulose
Lecithin
Phenethyl Alcohol
Poloxamer 188
Polycaprolactone
Sorbitan Laurate
Steareth-100
CI 40800
Chlorphenesin
Phenoxyethanol
Water, Glycerin, Butylene Glycol, Pentylene Glycol, Niacinamide, Cetyl Alcohol, Isohexadecane, Isononyl Isononanoate, Diisopropyl Sebacate, 2-Oleamido-1,3-Octadecanediol, 4-T-Butylcyclohexanol, Acetyl Dipeptide-1 Cetyl Ester, Adenosine, Ceramide NP, Hydroxypalmitoyl Sphinganine, Lauroyl Lysine, Octyldodecanol, Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate, Sodium Chloride, Sodium Hyaluronate, Sodium Hydroxide, Trisodium Ethylenediamine Disuccinate, Retinol, Tocopherol, Dicaprylyl Ether, Ammonium Polyacryloyldimethyl Taurate, Behenyl Alcohol, Caprylyl Glycol, Carbomer, Cetearyl Alcohol, Cetearyl Glucoside, Glycine Soja Oil, Helianthus Annuus Seed Oil, Hydroxyethylcellulose, Lecithin, Phenethyl Alcohol, Poloxamer 188, Polycaprolactone, Sorbitan Laurate, Steareth-100, CI 40800, Chlorphenesin, Phenoxyethanol
Caprylic/Capric Triglyceride
Diisopropyl Adipate
Dimethicone
1,2-Hexanediol
Acetyl Tetrapeptide-11
Acetyl Tetrapeptide-9
Ammonium Acryloyldimethyltaurate/Beheneth-25 Methacrylate Crosspolymer
Bisabolol
Butyrospermum Parkii Butter
C13-14 Isoparaffin
Caprylhydroxamic Acid
Cetearyl Dimethicone Crosspolymer
Dimethyl Isosorbide
Disodium EDTA
Glyceryl Stearate
Hydroxypinacolone Retinoate
Laureth-7
Limnanthes Alba Seed Oil
Macadamia Integrifolia Seed Oil
Mica
Moringa Oleifera Seed Oil
PEG-100 Stearate
Phytosphingosine
Polyacrylamide
Polysorbate 20
Tromethamine
Zingiber Officinale Root Extract
Parfum
CI 77491
Water, Caprylic/Capric Triglyceride, Glycerin, Diisopropyl Adipate, Pentylene Glycol, Dimethicone, Butylene Glycol, 4-T-Butylcyclohexanol, 1,2-Hexanediol, Acetyl Tetrapeptide-11, Acetyl Tetrapeptide-9, Ammonium Acryloyldimethyltaurate/Beheneth-25 Methacrylate Crosspolymer, Bisabolol, Butyrospermum Parkii Butter, C13-14 Isoparaffin, Caprylhydroxamic Acid, Carbomer, Ceramide NP, Cetearyl Dimethicone Crosspolymer, Dimethyl Isosorbide, Disodium EDTA, Glyceryl Stearate, Glycine Soja Oil, Hydroxypinacolone Retinoate, Laureth-7, Limnanthes Alba Seed Oil, Macadamia Integrifolia Seed Oil, Mica, Moringa Oleifera Seed Oil, PEG-100 Stearate, Phytosphingosine, Polyacrylamide, Polysorbate 20, Retinol, Sodium Hyaluronate, Tromethamine, Zingiber Officinale Root Extract, Parfum, Tocopherol, CI 77491
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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.
4-T-Butylcyclohexanol has skin soothing and perfuming/masking properties.
A study from 2016 found it to have skin-soothing properties both in-vivo and in-vitro. It works by intercepting the signals of irritation and can soothe the skin in a few minutes.
According to a manufacturer, this ingredient has a scent similar to musk or patchouli. Besides having a skin soothing effect, it can also help cover other unpleasant scents as a masking ingredient.
Butylene Glycol (or BG) is used within cosmetic products for a few different reasons:
Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.
Though this ingredient works well with most skin types, some people with sensitive skin may experience a reaction such as allergic rashes, closed comedones, or itchiness.
Carbomer is a synthetic thickening and gelling agent. It's basically the ingredient that gives a lot of serums, gels, creams, and sunscreens their smooth, non-sticky texture.
Although legally permitted at very high levels, carbomers are normally used at concentrations below 1%.
It also needs to be neutralized to actually thicken, and because it is a large molecule, it doesn't really penetrate the skin barrier.
Allergy-wise, the risk is very low. Clinical studies show carbomers have low potential for skin irritation/sensitization even at concentrations up to 100%.
A 2024 UK study patch-tested 1,302 patients and found true allergy to the parent group of carbomer to be rare with no confirmed relevant reactions.
Ceramide NP (formerly known as Ceramide 3) is one of the skin's naturally occurring lipids.
Since ceramides are the major lipid components of the skin, they are crucial for maintaining skin barrier and hydration. Ceramide NP most closely mirrors the dominant kind in human skin amongst ceramide subtypes.
This ceramide works by slotting into gaps within the stratum corneum's lipid matrix to limit trans-epidermal water loss (TEWL) and shield the skin against external irritants.
A study with 312 patients found that using a ceramide-containing routine for 4 weeks reduced the severity of atopic dermatitis by over 61%.
Another clinical study in subjects aged 60 and older found that a ceramide body wash and moisturizer improved skin dryness and itchy skin in 15 days.
Overall, ceramides are considered non-irritating and safety tests have found little to no observable adverse effects from using this ingredient.
Ceramide NP is usually sourced from plants (like soybean or rice bran), or produced synthetically.
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.
Glycine Soja Oil is a plant-derived oil from soybean seeds. Like other oils, it is rich in essential fatty acids (mostly linoleic and oleic) that support skin hydration and barrier function.
The fatty acids are able to integrate into the lipid matrix of the stratum corneum to help soften skin and reduce water loss.
On top of that, soybean oil is rich in vitamins like vitamin E, a potent antioxidant.
Research on soybean's active components also point to anti-inflammatory, collagen-stimulating, antioxidant activity, and protection against UV-induced oxidative damage.
Most of this research applies to the broader soybean plant and not just the oil fraction alone.
This ingredient may not be fungal acne safe due to the oleic acid content.
Pentylene Glycol (1,2-pentanediol) is a multitasking little diol with three main roles in a formula:
Research on alkanediols (the family pentylene glycol belongs to) show they work by disrupting microbial cell membranes. This disruption helps the primary preservative system in a product work more effectively at lower doses.
On the safety side, the Cosmetic Ingredient Review Expert Panel has concluded this ingredient to be safe as used in current cosmetic practices + concentrations.
Typical use levels in a formula run about 1-5%.
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.
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!