Paula's Choice Hydralight Moisture Infusing Lotion Versus Paula's Choice Rehydrating Moisture Mask

This ingredient is typically used in concentrations between 1-10%. Studies have found it to be non-sensitizing, non-phototoxic, and non-photoallergenic.

A close cousin of this ingredient is Glyceryl Stearate SE ("self-emulsifying"). This just has a small amount of sodium or potassium stearate added so it can emulsify without a co-emulsifier.

Since this ingredient is an ester of a C18 fatty acid, it may not be fungal acne safe. The Malassezia yeast can potentially metabolize within the C11-C24 range.

Fun fact: The human body also creates Glyceryl Stearate naturally.

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.

This ingredient has skin conditioning, anti-inflammatory, and humectant properties. Humectants help hydrate your skin by drawing moisture from the air. This helps keep your skin moisturized.

Potassium Sorbate, another commonly-used preservative, is the potassium salt of Sorbic Acid.

Sorbic Acid may worsen eczema. We recommend speaking with a professional if you have any concerns.

Potassium sorbate and sorbic acid can be found in baked goods, cheeses, dried meats, dried fruit, ice cream, pickles, wine, yogurt, and more.

Because it’s oil-soluble, THD dives deep into your skin’s fatty layers (think ceramides and cholesterol) to fight off the kind of free radicals that mess with your skin barrier. This makes it a great pair with water-based vitamin C (ascorbic acid) that mainly works on the surface.

Even at just 0.1%, THD is already showing great antioxidant activity. When used up to 2%, it helps keep your skin happy and calm, especially when it’s stressed from pollution or sun.

Want to fade dark spots or tackle hyperpigmentation? You’ll want 5% or more. Pairing it with brightening buddies like niacinamide or licorice root gives even better results. One study even used 30% THD with other brighteners and saw real results on stubborn discoloration, even in melasma-prone skin.

A note on THD: It’s has a slightly silky, oily texture and usually shows up colorless or pale yellow (though the exact shade can vary by supplier).

While you can sneak it into water-based formulas, it really shines when paired with silicones or oils, which help your skin soak it up better.

THD is pretty stable, but it’s still vulnerable to degradation like ascorbic acid. Too much light or heat (above 113°F / 45°C) can break it down over time. Go for dark and opaque packaging that keeps it safe and shady!

Read more about other types of Vitamin C:

Tocopheryl Acetate is commonly found in both skincare and dietary supplements.

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!