Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

The INKEY List Retinol Serum Versus Naturium Retinaldehyde Cream Serum 0.05%

The INKEY List Retinol Serum Versus Naturium Retinaldehyde Cream Serum 0.05% This anti-aging serum is formulated around Retinyl Acetate and Palmitoyl Tetrapeptide-7 to soften the look of wrinkles and refine skin texture. This anti-aging serum is formulated aro

The INKEY List Retinol Serum Versus Naturium Retinaldehyde Cream Serum 0.05%

This anti-aging serum is formulated around Retinyl Acetate and Palmitoyl Tetrapeptide-7 to soften the look of wrinkles and refine skin texture.

This anti-aging serum is formulated around Retinal 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

Propanediol

Dicaprylyl Carbonate

Retinyl Acetate

Dimethicone

Phenoxyethanol

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Caprylyl Glycol

Phospholipids

Squalane

Glycine Soja Oil

Carbomer

Polysorbate 60

Tocopheryl Acetate

Glycolipids

Sodium Hydroxide

Sodium Phytate

Sorbitan Isostearate

Glycine Soja Sterols

Tetrahexyldecyl Ascorbate

Leuconostoc/Radish Root Ferment Filtrate

Hyaluronic Acid

Sodium Lactate

Tocopherol

Polysorbate 20

Palmitoyl Tetrapeptide-7

Palmitoyl Tripeptide-1

Water, Glycerin, Butylene Glycol, Propanediol, Dicaprylyl Carbonate, Retinyl Acetate, Dimethicone, Phenoxyethanol, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Caprylyl Glycol, Phospholipids, Squalane, Glycine Soja Oil, Carbomer, Polysorbate 60, Tocopheryl Acetate, Glycolipids, Sodium Hydroxide, Sodium Phytate, Sorbitan Isostearate, Glycine Soja Sterols, Tetrahexyldecyl Ascorbate, Leuconostoc/Radish Root Ferment Filtrate, Hyaluronic Acid, Sodium Lactate, Tocopherol, Polysorbate 20, Palmitoyl Tetrapeptide-7, Palmitoyl Tripeptide-1

Triheptanoin

C13-15 Alkane

Coco-Caprylate/Caprate

Faex Extract

Apricot Kernel Oil Polyglyceryl-6 Esters

Soy Amino Acids

Punica Granatum Seed Extract

Cetyl Diglyceryl Tris(Trimethylsiloxy)Silylethyl Dimethicone

Hydrolyzed Yeast Extract

Olivine Extract

Dilinoleic Acid/Butanediol Copolymer

Cellulose

Sorbitan Oleate

Sodium Metabisulfite

Retinal

Guanosine

Uracil

Polyacrylate Crosspolymer-6

C9-12 Alkane

Polyglyceryl-10 Dipalmitate

Dipropylene Glycol

Glyceryl Polyacrylate

Pvm/Ma Copolymer

Adenosine Phosphate

Castor Oil/Ipdi Copolymer

Potassium Sorbate

Hexadecene

Sodium Benzoate

T-Butyl Alcohol

Water, Glycerin, Propanediol, Triheptanoin, C13-15 Alkane, Coco-Caprylate/Caprate, Carbomer, Faex Extract, Apricot Kernel Oil Polyglyceryl-6 Esters, Soy Amino Acids, Punica Granatum Seed Extract, Cetyl Diglyceryl Tris(Trimethylsiloxy)Silylethyl Dimethicone, Hydrolyzed Yeast Extract, Olivine Extract, Dilinoleic Acid/Butanediol Copolymer, Cellulose, Phenoxyethanol, Sorbitan Oleate, Sodium Metabisulfite, Retinal, Guanosine, Uracil, Polyacrylate Crosspolymer-6, C9-12 Alkane, Caprylyl Glycol, Polyglyceryl-10 Dipalmitate, Dipropylene Glycol, Sodium Hydroxide, Glyceryl Polyacrylate, Tocopherol, Pvm/Ma Copolymer, Adenosine Phosphate, Castor Oil/Ipdi Copolymer, Potassium Sorbate, Hexadecene, Sodium Benzoate, T-Butyl Alcohol

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.

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.

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.

Propanediol is an all-star ingredient. It softens, hydrates, and smooths the skin.

It’s often used to:

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.

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!

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. 03Tocopheryl Acetate is a stable, shelf-friendly form of vitamin E.
  4. 04Formulators 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.
  5. 05It'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.
  6. 06One 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.
  7. 07Once converted, vitamin E acts as a skin's main fat-soluble antioxidant that fights free radicals to protect skin from damage.
  8. 08Topical vitamin E generally boosts the skin's photoprotection, and it reduced UV-damage in animal models.
  9. 09This 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.
  10. 10Overall, 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.
  11. 11The 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.
  12. 12Most leave-on skincare keeps it at the lower end, often between 0.5-1%.
Source · skinsort.com
02

Product index

Related product references

03

Comparison edit

Read side by side