Hyaluronic Acid

Overview

Hyaluronic acid is a naturally occurring sugar molecule (a polysaccharide) found in human skin, joints, and connective tissue. In cosmetics it is almost always sold as its sodium salt — sodium hyaluronate — because the salt form is more stable, easier to handle, and slightly more skin-compatible. The INCI label says “Sodium Hyaluronate” 95% of the time even when the marketing says “Hyaluronic Acid.”

It is the most-talked-about humectant in modern skincare, and rightly so: it can hold up to 1000 times its weight in water. A finished serum with 0.5% sodium hyaluronate feels noticeably plump and slippery. The cosmetic-grade material is produced by fermentation of bacteria (typically Streptococcus zooepidemicus or Bacillus subtilis), so it is vegan and not animal-derived.

What it does in a formula

The molecular weight of the hyaluronate determines what it does on the skin:

• High molecular weight (HMW) — typically 1,000,000 to 1,500,000 daltons. Sits on the surface of the skin, forms a hydrating film, plumps and smooths instantly. Gives that “glass skin” feel within seconds. Cannot penetrate, so its effect is entirely topical.
• Low molecular weight (LMW) — around 50,000 to 300,000 daltons. Small enough to slip into the upper layers of the stratum corneum and hydrate from slightly below the surface. The plumping effect is less immediate but lasts longer.
• Ultra-low molecular weight (ULMW) — below 50,000 daltons, sometimes labeled “oligo” hyaluronic acid. Penetrates deeper. There is some debate (and some controversy) about whether ULMW HA can trigger mild inflammation in damaged skin, so it is mostly used at very low percentages.

The best DIY serums blend two or three weights — for example 0.3% HMW + 0.3% LMW — to hit the surface and the deeper layers in one formula.

How to use

Sodium hyaluronate is a powder. It is a stubborn powder. Dropped straight into water it forms little clumps with dry centers that take forever to hydrate. There are two reliable ways to handle it.

Method 1 — dispersion in a glycol. Mix the powder into propanediol or glycerin first (about 1 part powder to 10 parts glycol), stir until smooth, then add the slurry to your water phase. The glycol wets the particles individually so they cannot clump.

Method 2 — stock solution. Make a 1% hyaluronate stock in distilled water with a preservative (Liquid Germall Plus works). Let it hydrate overnight in the fridge. Add the finished stock to formulas at 10-50% inclusion (which gives you 0.1-0.5% HA in the final product).

Either way, hyaluronate gels take several hours to fully hydrate. Make ahead. It is also stable up to 80°C for short periods, so you can include it in heated water phases without losing performance.

Usage rate: 0.1-2% of pure powder. Most face serums sit at 0.3-0.5%. Above 1% the formula gets stringy and hard to spread.

Best for / Worst for

Best for: face serums, hydrating toners, sheet-mask soaks, post-acid soothing gels, mature-skin lotions, eye gels, any product where instant plumping is a selling point.

Worst for: heavy occlusive balms (no water for it to bind), oil cleansers, very low-pH (under 3) acid serums where the polymer can break down faster, dry-climate use without an occlusive on top (without humidity to draw from, HA can pull water from deeper skin and make things drier).

Common pitfalls

Clumping. The number-one beginner mistake. Always disperse in a glycol first, or hydrate as a stock solution. Never sprinkle powder into still water.

Drying effect in arid climates. HA pulls water from wherever it can find it. In low humidity, that includes the deeper layers of your own skin. Always seal a HA serum with a cream or oil-based moisturizer on top in dry weather.

Using the wrong weight. A high-molecular-weight powder marketed as “anti-aging penetrating serum” will not penetrate anything. Read the technical data sheet from your supplier.

Stringiness at high %. Above 1.5% the gel becomes too thick to spread evenly. If you want more plumping, blend weights rather than pushing one weight higher.

Substitutes

• Beta-glucan — also a polysaccharide humectant. Smoother feel, less plumping, more soothing.
• Sodium PCA — smaller molecule, lighter feel, less film-forming.
• Glycerin at higher percentages — much cheaper, similar surface hydration, no plumping film.
• Hydrolyzed hyaluronic acid — pre-broken into small fragments, sold as a deeper-penetrating alternative.