Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Estée Lauder Advanced Night Repair Synchronized Multi-Recovery Complex Serum

Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Estée Lauder Advanced Night Repair Synchronized Multi-Recovery Complex Serum This anti-aging serum is formulated around Niacinamide and Ceramide NP to soften the look of wrinkles and

Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide Versus Estée Lauder Advanced Night Repair Synchronized Multi-Recovery Complex Serum

This anti-aging serum is formulated around Niacinamide and Ceramide NP to soften the look of wrinkles and refine skin texture.

This barrier-repair serum is formulated around Bifida Ferment Lysate and Sodium Hyaluronate to strengthen the skin barrier and soften the look of wrinkles.

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

Bifida Ferment Lysate

PEG-8

Propanediol

Bis-PEG-18 Methyl Ether Dimethyl Silane

Methyl Gluceth-20

Glycereth-26

PEG-75

Adansonia Digitata Seed Extract

Tripeptide-32

Faex Extract

Lactobacillus Ferment

Cola Acuminata Seed Extract

Anthemis Nobilis Flower Extract

Hydrolyzed Algin

Pantethine

Caffeine

Sodium Rna

Bisabolol

Squalane

Oleth-3 Phosphate

Oleth-3

Oleth-5

Choleth-24

Hydrogenated Lecithin

Jojoba Wax PEG-120 Esters

Ceteth-24

Tocopheryl Acetate

Triethanolamine

Tetrasodium EDTA

BHT

Xanthan Gum

Potassium Sorbate

Disodium EDTA

CI 14700

CI 19140

Water, Bifida Ferment Lysate, PEG-8, Propanediol, Bis-PEG-18 Methyl Ether Dimethyl Silane, Methyl Gluceth-20, Glycereth-26, PEG-75, Butylene Glycol, Adansonia Digitata Seed Extract, Tripeptide-32, Sodium Hyaluronate, Faex Extract, Lactobacillus Ferment, Cola Acuminata Seed Extract, Anthemis Nobilis Flower Extract, Hydrolyzed Algin, Pantethine, Caffeine, Lecithin, Sodium Rna, Bisabolol, Squalane, Glycerin, Oleth-3 Phosphate, Caprylyl Glycol, Oleth-3, Oleth-5, Choleth-24, Hydrogenated Lecithin, Jojoba Wax PEG-120 Esters, Ceteth-24, Tocopheryl Acetate, Carbomer, Triethanolamine, Tetrasodium EDTA, BHT, Xanthan Gum, Potassium Sorbate, Disodium EDTA, Phenoxyethanol, CI 14700, CI 19140

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.

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.

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).

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.

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.

Lecithin is a term for a group of substances found in the cell membranes of plants, animals, and humans. They are made up of phospholipids.

Thanks to its amphiphilic structure (water-loving head and oil-loving tail), it is a true multitasker:

It plays well with most ingredients and is typically used at 0.1-1%. However, concentrations up to 50% have been reported in moisturizers.

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 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. 03Butylene Glycol (or BG) is used within cosmetic products for a few different reasons:
  4. 04Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.
  5. 05Though 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.
  6. 06Caprylyl Glycol is a humectant, skin conditioner, emollient, and preservative booster derived from either caprylic acid or synthetically created.
  7. 07Typical use levels vary from 0.3-1% as a preservative booster and go up to 2% to condition skin.
  8. 08Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).
  9. 09Glycerin (or glycerol) is a compound naturally found in your skin. It's a powerhouse humectant that pulls water into the stratum corneum.
  10. 10Topically, glycerin does several things at once:
  11. 11Your 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.
  12. 12Aquaporin-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.
  13. 13This 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.
  14. 14Just know very high concentrations (>40%) can feel tacky in low humidity.
  15. 15Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.
  16. 16Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate (long name, huh?) is a synthetic antioxidant.
  17. 17It is used to help stabilize other antioxidants or prevent the color from changing in a product.
  18. 18As an antioxidant, it helps fight free-radical molecules. Free-radical molecules are capable of damaging our cells and other genetic material. Thus, antioxidants may reduce the signs of aging.
  19. 19This ingredient is oil-soluble.
  20. 20Tocopherol is a fat-soluble antioxidant known as Vitamin E.
Source · skinsort.com
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Product index

Related product references

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Comparison edit

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