Hyaluronic acid: how to use it, and the mistake that dries you out

A humectant pulls water from wherever it can find it. In a dry European winter, that can mean your own skin — unless you apply it correctly.

Hyaluronic acid is a humectant: a molecule that binds water and holds it in place. Applied well it plumps the upper layers, softens fine lines within minutes and improves how everything layered on top feels. Applied badly it can leave skin tighter than before.

The mechanism behind that failure is simple. In low ambient humidity — a heated flat in Warsaw in January, an aircraft cabin, an air-conditioned office in Madrid — there is little water in the air to draw from, so the humectant draws from the deeper layers of your own skin and then lets it evaporate.

Two rules prevent it. Apply to damp skin, straight after cleansing, so the molecule has water to bind. Then seal immediately with a moisturiser or facial oil, which slows evaporation and locks the hydration in place. Hyaluronic acid without an occlusive on top is an unfinished step.

Molecular weight is worth knowing about but not worth obsessing over. High-molecular-weight HA sits on the surface and provides an immediate smoothing film; lower-weight fractions penetrate a little further for a longer-lasting effect. Good formulas use several weights, which the INCI list shows as Sodium Hyaluronate alongside Hydrolyzed Hyaluronic Acid or Sodium Hyaluronate Crosspolymer.

Finally, hydration is not the same as moisturisation. Hyaluronic acid adds water; ceramides, squalane and fatty acids keep it there. Skin that feels dehydrated in winter usually needs both, and adding a second humectant serum instead of a barrier cream is the most common way people make it worse.