Rachel Perry Celestial Glow Rejuvenating Serum Versus Kosas Plump + Juicy Vegan Collagen Spray-On Serum
This hydrating serum is formulated around Sodium Hyaluronate to hydrate skin and strengthen the skin barrier.
This barrier-repair serum is formulated around Lactobacillus Ferment to strengthen the skin barrier.
What's inside
What's inside
Key Ingredients
Benefits
Concerns
Ingredients Side-by-side
Water
Skin ConditioningCitrus Aurantium Dulcis Fruit Water
MaskingPropanediol
SolventPolyglyceryl-6 Caprylate
EmulsifyingPolyglyceryl-4 Caprate
EmulsifyingGlycerin
HumectantParfum
MaskingPolyglyceryl-3 Cocoate
EmulsifyingPolyglyceryl-6 Ricinoleate
EmulsifyingTamarindus Indica Seed Polysaccharide
Skin ConditioningCaprylic/Capric Triglyceride
MaskingPentylene Glycol
Skin ConditioningCaprylyl Glycol
EmollientSodium Hyaluronate
HumectantSodium Levulinate
Skin ConditioningLavandula Oil/Extract
Pelargonium Graveolens Flower Oil
MaskingSodium Anisate
AntimicrobialPunica Granatum Pericarp Extract
Skin ConditioningLinalool
PerfumingCitric Acid
BufferingLinalyl Acetate
MaskingCitronellol
PerfumingGeraniol
PerfumingPinene
MaskingSempervivum Tectorum Extract
Skin ConditioningBeta-Caryophyllene
MaskingTerpineol
MaskingGeranyl Acetate
PerfumingCamphor
MaskingCitral
PerfumingLimonene
PerfumingCynara Scolymus Leaf Extract
Skin ConditioningOcimum Tenuiflorum Extract
Skin ConditioningCapparis Spinosa Fruit Extract
Skin ConditioningWater, Citrus Aurantium Dulcis Fruit Water, Propanediol, Polyglyceryl-6 Caprylate, Polyglyceryl-4 Caprate, Glycerin, Parfum, Polyglyceryl-3 Cocoate, Polyglyceryl-6 Ricinoleate, Tamarindus Indica Seed Polysaccharide, Caprylic/Capric Triglyceride, Pentylene Glycol, Caprylyl Glycol, Sodium Hyaluronate, Sodium Levulinate, Lavandula Oil/Extract, Pelargonium Graveolens Flower Oil, Sodium Anisate, Punica Granatum Pericarp Extract, Linalool, Citric Acid, Linalyl Acetate, Citronellol, Geraniol, Pinene, Sempervivum Tectorum Extract, Beta-Caryophyllene, Terpineol, Geranyl Acetate, Camphor, Citral, Limonene, Cynara Scolymus Leaf Extract, Ocimum Tenuiflorum Extract, Capparis Spinosa Fruit Extract
Water
Skin ConditioningPropanediol
SolventPentylene Glycol
Skin ConditioningGlycerin
HumectantPhenethyl Alcohol
MaskingHydrolyzed Rice Protein
Skin ConditioningHydrolyzed Vegetable Protein
Skin ConditioningPolyglyceryl-6 Caprylate
EmulsifyingPolyglyceryl-3 Cocoate
EmulsifyingPolyglyceryl-4 Caprate
EmulsifyingPolyglyceryl-6 Ricinoleate
EmulsifyingSodium Gluconate
Skin ConditioningErythritol
HumectantHydrolyzed Pea Protein
EmollientCaprylic/Capric Triglyceride
MaskingMaltodextrin
AbsorbentAcacia Seyal Gum Extract
HumectantLactobacillus Ferment
Skin ConditioningArtemisia Capillaris Flower Extract
Skin ConditioningHibiscus Sabdariffa Fruit Extract
Hibiscus Sabdariffa Flower Extract
Skin ConditioningGlycine
BufferingProline
Skin ConditioningHydrolyzed Sodium Hyaluronate
Skin ConditioningSodium Hyaluronate
HumectantPalmitoyl Tripeptide-37
Skin ConditioningPotassium Sorbate
PreservativeCitric Acid
BufferingBenzyl Alcohol
PerfumingSodium Benzoate
MaskingWater, Propanediol, Pentylene Glycol, Glycerin, Phenethyl Alcohol, Hydrolyzed Rice Protein, Hydrolyzed Vegetable Protein, Polyglyceryl-6 Caprylate, Polyglyceryl-3 Cocoate, Polyglyceryl-4 Caprate, Polyglyceryl-6 Ricinoleate, Sodium Gluconate, Erythritol, Hydrolyzed Pea Protein, Caprylic/Capric Triglyceride, Maltodextrin, Acacia Seyal Gum Extract, Lactobacillus Ferment, Artemisia Capillaris Flower Extract, Hibiscus Sabdariffa Fruit Extract, Hibiscus Sabdariffa Flower Extract, Glycine, Proline, Hydrolyzed Sodium Hyaluronate, Sodium Hyaluronate, Palmitoyl Tripeptide-37, Potassium Sorbate, Citric Acid, Benzyl Alcohol, Sodium Benzoate
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%.
Learn more about Caprylic/Capric TriglycerideCitric Acid is an alpha hydroxy acid (AHA) naturally found in citrus fruits like oranges, lemons, and limes.
Like other AHAs, citric acid can exfoliate skin by breaking down the bonds that hold dead skin cells together. This helps reveal smoother and brighter skin underneath.
However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.
Due to this, citric acid is usually included in small amounts as a pH adjuster. This helps keep products slightly more acidic and compatible with skin's natural pH.
In skincare formulas, citric acid can:
While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.
Most citric acid used in skincare today is made by fermenting sugars (usually from molasses). This synthetic version is identical to the natural citrus form but easier to stabilize and use in formulations.
Rosacea skin has a lower threshold for acids generally, with 62.5% of rosacea subjects in one study reacting to lactic acid in a sting test. This is why we mark citric acid as a potential rosacea trigger.
However, this ingredient shows up as a pH adjuster or chelator at roughly 0.1-1% in many products. These low levels are unlikely to be an issue for rosacea skin and becomes a potential trigger at exfoliating concentrations (20%). Because everybody's skin is unique, we recommend a patch test if you are unsure.
Learn more about Citric AcidGlycerin (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 GlycerinPentylene 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 GlycolPolyglyceryl-3 Cocoate isn't fungal acne safe. It can be bad for dry skin.
Polyglyceryl-4 Caprate comes from Capric Acid and Polyglycerin-4. It is an emulsifier.
Emulsifiers help stabilize a product. They do this by preventing ingredients from separating, such as oils and water which do not mix naturally.
Polyglyceryl-6 Caprylate comes from caprylic acid and Polyglycerin-6. It is an emulsifier, emollient, and cleansing agent.
Emulsifiers help stabilize a product. It does this by preventing certain ingredients from separating. Common ingredients include oils and water, which do not mix naturally. Emulsifiers have properties that help keep ingredients such as these together. There is emerging research that shows emulsifiers may also help in delivering ingredients into the skin.
As an emollient, polyglyceryl-6 caprylate helps soften skin.
Learn more about Polyglyceryl-6 CaprylatePolyglyceryl-6 Ricinoleate isn't fungal acne safe.
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.
Learn more about PropanediolSodium 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