Kiehl's Ultra Pure High-Potency 5.0% Niacinamide Serum Versus PCA Skin Hyaluronic Acid Boosting Serum

Kiehl's Ultra Pure High-Potency 5.0% Niacinamide Serum Versus PCA Skin Hyaluronic Acid Boosting Serum

This oil-control serum is formulated around Niacinamide to balance excess oil and refine the look of pores.

This hydrating serum is formulated around Niacinamide and Sodium Hyaluronate to hydrate skin and strengthen the skin barrier.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Niacinamide

Glycerin

Propanediol

Methyl Gluceth-20

Hydroxyacetophenone

Sodium Hyaluronate

Caprylyl Glycol

Carbomer

Sodium Hydroxide

Water, Niacinamide, Glycerin, Propanediol, Methyl Gluceth-20, Hydroxyacetophenone, Sodium Hyaluronate, Caprylyl Glycol, Carbomer, Sodium Hydroxide

Dimethicone

Hydrolyzed Yeast Extract

Polyglyceryl-3 Beeswax

Coconut Alkanes

Phenoxyethanol

Isododecane

Jojoba Esters

Dimethicone Crosspolymer

Polysilicone-11

Sodium Benzoate

Xanthan Gum

Hydrolyzed Hyaluronic Acid

Cetyl Alcohol

Polyglyceryl-6 Distearate

Sodium Lauroyl Lactylate

Disodium Acetyl Glucosamine Phosphate

Hydrolyzed Glycosaminoglycans

Ethylhexylglycerin

Hexylene Glycol

Polygonum Bistorta Root Extract

Cetyl Hydroxyethylcellulose

Rosmarinus Officinalis Leaf Oil

Aroma

Polyglucuronic Acid

Ceramide NP

Hyaluronic Acid

Sodium Carrageenan

Ceramide AP

Phytosphingosine

Cholesterol

Lecithin

Maris Sal

Ceramide EOP

Water, Propanediol, Glycerin, Niacinamide, Dimethicone, Hydrolyzed Yeast Extract, Polyglyceryl-3 Beeswax, Coconut Alkanes, Phenoxyethanol, Isododecane, Jojoba Esters, Dimethicone Crosspolymer, Polysilicone-11, Sodium Hyaluronate, Sodium Benzoate, Carbomer, Xanthan Gum, Hydrolyzed Hyaluronic Acid, Cetyl Alcohol, Polyglyceryl-6 Distearate, Sodium Lauroyl Lactylate, Disodium Acetyl Glucosamine Phosphate, Hydrolyzed Glycosaminoglycans, Ethylhexylglycerin, Sodium Hydroxide, Hexylene Glycol, Polygonum Bistorta Root Extract, Cetyl Hydroxyethylcellulose, Rosmarinus Officinalis Leaf Oil, Aroma, Polyglucuronic Acid, Ceramide NP, Hyaluronic Acid, Sodium Carrageenan, Ceramide AP, Phytosphingosine, Caprylyl Glycol, Cholesterol, Lecithin, Maris Sal, Ceramide EOP

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.

Niacinamide is a multitasking form of vitamin B3 that strengthens the skin barrier, reduces pores and dark spots, regulates oil, and improves signs of aging.

And the best part? It's gentle and well-tolerated by most skin types, including sensitive and reactive skin.

You might have heard of "niacin flush", or the reddening of skin that causes itchiness. Niacinamide has not been found to cause this.

In very rare cases, some individuals may not be able to tolerate niacinamide at all or experience an allergic reaction to it.

If you are experiencing flaking, irritation, and dryness with this ingredient, be sure to double check all your products as this ingredient can be found in all categories of skincare.

When incorporating niacinamide into your routine, look out for concentration amounts. Typically, 5% niacinamide provides benefits such as fading dark spots. However, if you have sensitive skin, it is better to begin with a smaller concentration.

When you apply niacinamide to your skin, your body converts it into nicotinamide adenine dinucleotide (NAD). NAD is an essential coenzyme that is already found in your cells as "fuel" and powers countless biological processes.

In your skin, NAD helps repair cell damage, produce new healthy cells, support collagen production, strengthen the skin barrier, and fight environmental stressors (like UV and pollution).

Our natural NAD levels start to decline with age, leading to slower skin repair, visible aging, and a weaker skin barrier. By providing your skin niacinamide, you're recharging your skin's NAD levels. This leads to stronger, healthier, and younger looking skin.

Another name for vitamin B3 is nicotinamide. This vitamin is water-soluble and our bodies don't store it. We obtain Vitamin B3 from either food or skincare. Meat, fish, wheat, yeast, and leafy greens contain vitamin B3.

The type of niacinamide used in skincare is synthetically created.

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 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.

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.

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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