The INCI Decoder : Hyaluronic Acid, HA, Hydrolyzed Hyaluronic Acid, Sodium Hyaluronate

How to Choose Your Hydrating Serum?

Look at the size of the molecules — that’s what really matters

Hyaluronic acid comes in different molecular weights, and each size plays a role. There are actually three main sizes:

- High molecular weight stays on the surface of the skin, forming a moisturizing film and giving an instant plumping effect.

- Medium molecular weight penetrates slightly deeper 

- Low molecular weight penetrates deeper, delivering long-term hydration and supporting elasticity

A good serum doesn’t rely on just one size of hyaluronic acid molecules. While you might assume it needs all three sizes, the most effective formulas focus on the two size of molecules that matter most: lower and higher. This layered approach creates a cushion of moisture that delivers deep, lasting hydration   — imagine a pillow for your skin, soft, supportive, and always comforting.

The Modern (and Clean) Hyaluronic Acid origin

Today, most hyaluronic acid used in skincare today is made via biotechnology, not animal sources. It's typically produced through bacterial fermentation, especially using strains like Streptococcus zooepidemicus or Bacillus subtilis. These bacteria are cultured in a nutrient-rich medium, and then the hyaluronic acid they produce is harvested, purified, and formulated into skincare products.

This method is:
- Vegan-friendly (unlike older methods that extracted it from rooster combs),

- More sustainable and consistent,

- and Better for sensitive skin, as it reduces risk of contamination or immune reaction.

Thanks to fermentation, the resulting hyaluronic acid is highly pure, vegan, and mimics what your body produces — without compromise.

And then there’s the French touch. In some of the formulas I work with, we go a step further: we use a premium, COSMOS-approved hyaluronic acid derived from the fermentation of wheat.

It wasn’t always so clean and gentle. Years ago, hyaluronic acid was typically extracted from animal sources — most commonly from rooster combs. Yes, the fleshy red crest on top of a rooster’s head. It sounds surprising, but that method was widely used for a long time, especially in the pharmaceutical world.

Hyaluronic Acid Serum

Not Magic, Just Molecules: Why Hyaluronic Acid Works

IIn its raw form, Hyaluronic acid is a fine, almost weightless white powder (at least the one we source in France). When mixed with water, the molecules swell and transform into a gel-like texture. It takes us about two hours to make two liters of gel.

This transformation is key: hyaluronic acid can hold up to 1,000 times its weight in water. Once applied to your skin, it acts like a moisture magnet, drawing hydration into the upper layers.

So now you know how it works, what’s the best kind of hyaluronic acid serum? My answer is simple: your serum should combine both small and large molecule sizes — and include key ingredients like Vitamin B5 but also Glycerin and Cucumber extracts to lock in hydration and soothe the skin.