Principia Sérum Facial αA-2 Versus SLMD Hyaluronic Acid Serum

Principia Sérum Facial αA-2 Versus SLMD Hyaluronic Acid Serum

This brightening serum is formulated around Gluconolactone and Alpha-Arbutin to fade the look of dark spots and brighten dull-looking skin.

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

What's inside

Key Ingredients

Benefits

Concerns

No concerns

Ingredients Side-by-side

Water

Xanthan Gum

Propanediol

Disodium EDTA

Sodium Hyaluronate

Gluconolactone

Alpha-Arbutin

Phenoxyethanol

Caprylyl Glycol

Water, Xanthan Gum, Propanediol, Disodium EDTA, Sodium Hyaluronate, Gluconolactone, Alpha-Arbutin, Phenoxyethanol, Caprylyl Glycol

Squalane

Ethylhexyl Palmitate

Silica Dimethyl Silylate

Butylene Glycol

Hexylene Glycol

Squalane, Sodium Hyaluronate, Ethylhexyl Palmitate, Silica Dimethyl Silylate, Butylene Glycol, Caprylyl Glycol, Hexylene Glycol, Phenoxyethanol

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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.

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).

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.

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.

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