Hydrating serum is a category that includes products with completely different mechanisms — from humectants that attract water from deep layers to actives that replenish barrier lipids. Choosing a serum without understanding which mechanism your skin needs is like buying medication without reading the therapeutic indication.

Different Hydration Mechanisms in Serum Form

Humectants (Attract Water)

Hyaluronic acid, vegetable glycerin, sodium PCA, beta-glucan. They need ambient moisture to function. Without an occlusive layer on top, hydration evaporates within 30–40 minutes.

Barrier Actives (Retain Water)

Prebiotics, ceramides in serum, lightweight fatty acids. They don't hydrate directly — they strengthen skin's capacity to retain the water already there. More lasting efficacy but less immediate results.

Combined (Attract + Retain)

The best approach: humectant + barrier in the same serum or two products in sequence. Prebiotic + HA is the most effective combination — prebiotics reinforce barrier while HA hydrates immediately.

Serum vs. Cream: Which First?

Always serum first — lighter textures penetrate before denser layers. Cream on top seals what the serum did. The wrong sequence (cream over serum over cream) creates competing absorption layers.

For Very Dry Skin: The Sandwich Technique

Apply HA to slightly damp skin → wait 30 seconds → occlusive moisturiser on top immediately. The occlusive layer seals the HA and the moisture it absorbed.