The INKEY List Advanced Retinal Serum Versus Medik8 Crystal Retinal

The INKEY List Advanced Retinal Serum Versus Medik8 Crystal Retinal

This anti-aging serum is formulated around 4-T-Butylcyclohexanol and Retinal to soften the look of wrinkles and refine skin texture.

This anti-aging serum is formulated around Retinal and 3-O-Ethyl Ascorbic Acid to soften the look of wrinkles and refine skin texture.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Glycerin

Caprylic/Capric Triglyceride

Dicaprylyl Carbonate

Polyglyceryl-6 Stearate

Isohexadecane

Sodium Polyacryloyldimethyl Taurate

Cetearyl Alcohol

Mangifera Indica Seed Butter

Cucumis Sativus Fruit Extract

Phenoxyethanol

Dipropylene Glycol

Pentylene Glycol

Glyceryl Caprylate

Diisopropyl Sebacate

Glyceryl Stearate

4-T-Butylcyclohexanol

Polyglyceryl-6 Behenate

Retinal

Sorbeth-30 Tetraoleate

Tocophersolan

Tocopheryl Acetate

Caprylhydroxamic Acid

Ethylhexylglycerin

Bacillus Ferment

Lactic Acid

Sodium Benzoate

Dimethylmethoxy Chromanol

Water, Glycerin, Caprylic/Capric Triglyceride, Dicaprylyl Carbonate, Polyglyceryl-6 Stearate, Isohexadecane, Sodium Polyacryloyldimethyl Taurate, Cetearyl Alcohol, Mangifera Indica Seed Butter, Cucumis Sativus Fruit Extract, Phenoxyethanol, Dipropylene Glycol, Pentylene Glycol, Glyceryl Caprylate, Diisopropyl Sebacate, Glyceryl Stearate, 4-T-Butylcyclohexanol, Polyglyceryl-6 Behenate, Retinal, Sorbeth-30 Tetraoleate, Tocophersolan, Tocopheryl Acetate, Caprylhydroxamic Acid, Ethylhexylglycerin, Bacillus Ferment, Lactic Acid, Sodium Benzoate, Dimethylmethoxy Chromanol

Isododecane

Cetearyl Olivate

Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

PPG-12/Smdi Copolymer

Sorbitan Olivate

Squalane

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Hydroxyacetophenone

Cyclodextrin

3-O-Ethyl Ascorbic Acid

Sodium Polyaspartate

Hydroxypropyl Methylcellulose

Sodium Hyaluronate

Tetrahexyldecyl Ascorbate

Daucus Carota Sativa Seed Oil

Alumina

Isostearic Acid

Lecithin

Polyglyceryl-3 Polyricinoleate

Polyhydroxystearic Acid

Lonicera Japonica Flower Extract

Lonicera Caprifolium Flower Extract

Stearic Acid

Citric Acid

BHT

Rubus Chamaemorus Seed Oil

Polysorbate 60

Disodium EDTA

Sorbitan Isostearate

Vanilla Planifolia Fruit Extract

Dipteryx Odorata Bean Extract

Coumarin

CI 14700

CI 77891

Water, Caprylic/Capric Triglyceride, Glycerin, Isododecane, Cetearyl Olivate, Sodium Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Cetearyl Alcohol, PPG-12/Smdi Copolymer, Sorbitan Olivate, Tocopheryl Acetate, Squalane, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Hydroxyacetophenone, Cyclodextrin, 3-O-Ethyl Ascorbic Acid, Sodium Polyaspartate, Hydroxypropyl Methylcellulose, Sodium Hyaluronate, Phenoxyethanol, Tetrahexyldecyl Ascorbate, Daucus Carota Sativa Seed Oil, Retinal, Alumina, Isostearic Acid, Lecithin, Polyglyceryl-3 Polyricinoleate, Polyhydroxystearic Acid, Lonicera Japonica Flower Extract, Lonicera Caprifolium Flower Extract, Stearic Acid, Citric Acid, BHT, Rubus Chamaemorus Seed Oil, Polysorbate 60, Disodium EDTA, Ethylhexylglycerin, Sorbitan Isostearate, Pentylene Glycol, Vanilla Planifolia Fruit Extract, Dipteryx Odorata Bean Extract, Coumarin, CI 14700, CI 77891

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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.

Caprylic/Capric Triglyceride (aka MCT Oil) is a lightweight emollient, solvent, and texture enhancer. It is considered a skin-softener by helping to prevent moisture loss.

Though it behaves like an oil, it is not technically one due to its chemical composition. One perk of this ingredient is that it is very stable, resistant to oxidation, and unlikely to go rancid.

In practice, that translates to a long shelf life and a consistently elegant skin feel.

While there is an assumption Caprylic Triglyceride can clog pores due to it being derived from coconut oil, there is no research supporting this. Just patch test if you have concerns.

Fractionated coconut oil and MCT Oil are both listed as Caprylic/Capric Triglyceride according to INCI. This is because INCI names are based on the ingredient’s final chemical composition and not its marketing name or source.

This ingredient is treated as the gold standard fungal acne safe oil. Even though it is coconut derived, the problematic lauric acid is stripped out.

This leaves just caprylic (C8) and capric (C10) acid. These chain lengths actually trend antifungal; a 2020 study found caprylic acid was enough to disrupt Malassezia furfur cell membrane, with a caprylic acid derivative damaging membrane structures at concentrations as low as 0.2%.

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.

Ethylhexylglycerin is created from glycerin. It is a multitasker ingredient that:

The CIR Expert Panel found minimal skin absorption or sensitization of any kind in a safety assessment. Though this ingredient is considered well-tolerated, a small number of cases of allergic dermatitis have been published since 2002. Just be sure to patch test if you are unsure.

Industry-reported use ranges from 8% in rinse-off products and 2% in leave-on formulations.

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.

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%.

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.

Retinal (aka retinaldehyde) is a form of retinoid that formulators use mainly as an antiaging and skin-renewing active.

What makes it special is its position in the retinoid family; skin converts it to retinoic acid (the prescription gold standard) in just one step.

Because retinal only requires 1 conversion step to become retinoic acid, it's the strongest over-the-counter retinoid. It also works at lower concentrations than retinol, since retinal is about 10x more bioavailable.

Studies back up its efficacy in skin:

A foundational trial showed that applying 0.05-0.5% retinal for 1-3 months produced a dose-dependent and significant increase in epidermal thickness + cell turnover markers.

And a head-to-head comparison of 0.05% retinal against a 0.05% retinoid acid found both formulations were effective for the basis of wrinkle/skin roughness features, but retinoic acid caused more local irritation.

More recent controlled trials confirm it improves wrinkles, dermal density, and firmness over 12-24 weeks, with significant improvements in skin texture and firmness (particularly with the higher 0.1% concentration).

Retinal also has one trick the other retinoids do not: it directly fights against acne bacteria since a clinical study showed retinaldehyde-treated areas displayed a significant decrease in counts of viable P. acnes.

This makes it a great pick for people who want to treat aging and breakouts.

Typical cosmetic use sits in the 0.05-0.1% range with 0.05% being the gentle starting point and 0.1% giving stronger results.

Like all retinoids, retinal works best with nightly use, a good moisturizer, and daytime sunscreen. It can cause some irritation so ease into it slowly rather than going all in.

The "ramp up" method works well: start with Retinal 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.

Tocopheryl Acetate is a stable, shelf-friendly form of vitamin E.

Formulators love it because plain vitamin E oxidizes quickly once it hits air. This acetate version stays stable and resists going off, helping to extend a product's shelf life.

It's actually inactive on its own and works like a slow-release "storage" form; the enzymes in your skin called esterases gradually convert it into active vitamin E over time.

One in vivo study showed 5% of the acetate in the living layer of the epidermis converted to vitamin E after 5 days of application. This study also found the skin gained protection against UV damage even though the conversion was slow and small.

Once converted, vitamin E acts as a skin's main fat-soluble antioxidant that fights free radicals to protect skin from damage.

Topical vitamin E generally boosts the skin's photoprotection, and it reduced UV-damage in animal models.

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.

Overall, it has a pretty solid safety profile and has been found to be non-irritating and non-comedogenic. Allergic reactions may happen but stay rare due to how widely the ingredient gets used.

The concentration will vary depending on the formula; industry data shows 0.1% in baby lotions, 3% in lipsticks, and 5% in foot powders. You can also find this ingredient at 100% in a pure vitamin E oil.

Most leave-on skincare keeps it at the lower end, often between 0.5-1%.

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!

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