Hyaluronic Acid

Sodium hyaluronate is the salt form of hyaluronic acid, a polysaccharide that occurs naturally in skin, where it sits in the extracellular matrix and holds water between cells.

How it works

Hyaluronic acid holds water through hydrogen bonding along its molecular chain. It draws moisture from two sources: the environment when humidity is high, and the deeper layers of skin when it is not.

That second route is worth understanding. In dry conditions, a humectant on the skin surface can pull water upward from the epidermis rather than inward from the air, which is why hyaluronic acid is usually applied to damp skin and sealed with an occlusive or emollient layer.

Molecular weight

Hyaluronic acid is manufactured across a wide range of molecular weights, and the differences are meaningful.

High molecular weight forms remain on the surface, where they form a hydrating film and reduce water loss. Low molecular weight forms are smaller and can move further into the upper layers of the epidermis. Many formulas combine several weights to work at different depths.

Molecular weight is rarely disclosed on packaging, so an ingredient list showing sodium hyaluronate tells you the ingredient is present but not how it behaves.

Acid versus salt

Sodium hyaluronate and hyaluronic acid are frequently used interchangeably in marketing. The salt form is more stable, more soluble in water, and smaller, so it is what appears in most formulas regardless of what the front of the pack says.