Medik8 Crystal Retinal Versus Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides and Peptide
This anti-aging serum is formulated around 3-O-Ethyl Ascorbic Acid and Tetrahexyldecyl Ascorbate to soften the look of wrinkles and refine skin texture.
This anti-aging serum is formulated around Niacinamide and Ceramide NP to soften the look of wrinkles and refine skin texture.
What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Water
Skin ConditioningCaprylic/Capric Triglyceride
Masking
Glycerin
Humectant
Isododecane
EmollientCetearyl Olivate
Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer
Emulsion StabilisingCetearyl Alcohol
Emollient
PPG-12/Smdi Copolymer
EmollientSorbitan Olivate
Emulsifying
Tocopheryl Acetate
Antioxidant
Cyclodextrin
AbsorbentSqualane
Emollient
Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer
Emulsion StabilisingHydroxyacetophenone
Antioxidant
3-O-Ethyl Ascorbic Acid
Skin Conditioning
Hydroxypropyl Methylcellulose
Emulsion StabilisingSodium Hyaluronate
Humectant
Phenoxyethanol
Preservative
Tetrahexyldecyl Ascorbate
Antioxidant
Daucus Carota Sativa Seed Oil
Emollient
Retinal
Skin Conditioning
Rubus Chamaemorus Seed Oil
Skin Conditioning
Alumina
Abrasive
Isostearic Acid
Cleansing
Lecithin
Emollient
Polyglyceryl-3 Polyricinoleate
Emulsifying
Lonicera Japonica Flower Extract
Skin ConditioningLonicera Caprifolium Flower Extract
Perfuming
Polyhydroxystearic Acid
Emulsifying
Stearic Acid
Cleansing
Sodium Polyaspartate
HumectantPentylene Glycol
Skin Conditioning
Citric Acid
Buffering
Polysorbate 60
Emulsifying
Disodium EDTA
Ethylhexylglycerin
Skin ConditioningBHT
Antioxidant
Sorbitan Isostearate
Emulsifying
Vanilla Planifolia Fruit Extract
Skin Conditioning
Dipteryx Odorata Bean Extract
Masking
Coumarin
Perfuming
CI 14700
Cosmetic ColorantCI 77891
Cosmetic ColorantWater, Caprylic/Capric Triglyceride, Glycerin, Isododecane, Cetearyl Olivate, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Cetearyl Alcohol, PPG-12/Smdi Copolymer, Sorbitan Olivate, Tocopheryl Acetate, Cyclodextrin, Squalane, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Hydroxyacetophenone, 3-O-Ethyl Ascorbic Acid, Hydroxypropyl Methylcellulose, Sodium Hyaluronate, Phenoxyethanol, Tetrahexyldecyl Ascorbate, Daucus Carota Sativa Seed Oil, Retinal, Rubus Chamaemorus Seed Oil, Alumina, Isostearic Acid, Lecithin, Polyglyceryl-3 Polyricinoleate, Lonicera Japonica Flower Extract, Lonicera Caprifolium Flower Extract, Polyhydroxystearic Acid, Stearic Acid, Sodium Polyaspartate, Pentylene Glycol, Citric Acid, Polysorbate 60, Disodium EDTA, Ethylhexylglycerin, BHT, Sorbitan Isostearate, Vanilla Planifolia Fruit Extract, Dipteryx Odorata Bean Extract, Coumarin, CI 14700, CI 77891
Water
Skin ConditioningGlycerin
Humectant
Butylene Glycol
Humectant
Pentylene Glycol
Skin Conditioning
Niacinamide
Smoothing
Cetyl Alcohol
Emollient
Isohexadecane
EmollientIsononyl Isononanoate
EmollientDiisopropyl Sebacate
Emollient2-Oleamido-1,3-Octadecanediol
Skin Conditioning4-T-Butylcyclohexanol
Masking
Acetyl Dipeptide-1 Cetyl Ester
Skin Conditioning
Adenosine
Skin Conditioning
Ceramide NP
Skin Conditioning
Hydroxypalmitoyl Sphinganine
Skin Conditioning
Lauroyl Lysine
Skin Conditioning
Octyldodecanol
Emollient
Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate
Antioxidant
Sodium Chloride
MaskingSodium Hyaluronate
Humectant
Sodium Hydroxide
BufferingTrisodium Ethylenediamine Disuccinate
Retinol
Skin Conditioning
Tocopherol
Antioxidant
Dicaprylyl Ether
Emollient
Ammonium Polyacryloyldimethyl Taurate
Emulsion StabilisingBehenyl Alcohol
Emollient
Caprylyl Glycol
Emollient
Carbomer
Emulsion StabilisingCetearyl Alcohol
Emollient
Cetearyl Glucoside
Emulsifying
Glycine Soja Oil
Emollient
Helianthus Annuus Seed Oil
Emollient
Hydroxyethylcellulose
Emulsion StabilisingLecithin
Emollient
Phenethyl Alcohol
MaskingPoloxamer 188
EmulsifyingPolycaprolactone
StabilisingSorbitan Laurate
Emulsifying
Steareth-100
Gel FormingCI 40800
Cosmetic ColorantChlorphenesin
Antimicrobial
Phenoxyethanol
Preservative
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
Reviews
Ingredients Explained
These ingredients are found in both products.
Ingredients higher up in an ingredient list are typically present in a larger amount.
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.
Learn more about Cetearyl AlcoholGlycerin (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.
Learn more about GlycerinLecithin 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.
Learn more about LecithinPentylene 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%.
Learn more about Pentylene GlycolPhenoxyethanol 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.
Learn more about PhenoxyethanolSodium 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.
Learn more about Sodium HyaluronateWater. 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!
Learn more about Water
