Hyaluronic acid: real hydration or just a cosmetic effect?

Reading time: 7-9 min

Important note: this article provides general cosmetic and scientific information. It is not a substitute for medical advice and does not constitute a diagnosis.

Introduction

Hyaluronic acid is everywhere: "plumping" serums, "24h hydration" creams, "instant glow" masks. It has become the symbol of hydration.

But there's a legitimate question: does it really moisturize the skin... or does it mainly provide a cosmetic effect (smoother surface, immediate comfort) that disappears as soon as you stop?

The scientific answer is nuanced, and that's precisely what makes it useful. Yes, hyaluronic acid can improve hydration parameters. No, it does not "repair" a weakened barrier on its own. It works best as part of a complete strategy: humectants + barrier + protection.

Hyaluronic acid: what exactly is it?

Hyaluronic acid (HA) is a glycosaminoglycan naturally present in the skin, notably in the dermis, where it forms part of the extracellular matrix. Its most famous property is its ability to retain water, which contributes to hydration and tissue suppleness.

In cosmetics, we're not talking about a single HA, but a family: different molecular sizes, sometimes cross-linked, with different behaviors on the skin surface.

High-molecular-weight HA vs. low-molecular-weight HA

• High molecular weight: tends to stay more on the surface, film-forming effect, comfort, reduced feeling of tightness.
• Low molecular weight: may interact differently with the stratum corneum; its benefit is highly dependent on formulation, tolerance and context of use.

This point is essential: perceived efficacy often depends more on the overall formulation than on the "percentage" displayed.

Hydration: what does it mean scientifically?

In everyday language, "hydrate" means "to give water to the skin". In cutaneous biophysics, it's more precise:

• Hydration of the stratum corneum: quantity of water in the most superficial layer (measurable, for example, by corneometry).
• Water loss (TEWL ): speed at which water evaporates through the skin. The higher the TEWL, the more fragile the barrier.

An active ingredient can increase hydration (more water "retained") without necessarily improving TEWL. This is often where the illusion arises: immediate comfort, but a barrier that's still unstable if there's nothing to support it.

What studies on topical hyaluronic acid really show

Publications on topical HA suggest that it can :

• increase stratum corneum hydration,
• improve surface appearance (smoothness, suppleness),
• temporarily reduce the appearance of fine dehydration lines,
• contribute to improved skin comfort.

These benefits are consistent with its role as ahumectant and, in certain forms, as a film-forming agent.

But the literature also makes one point: in the case of a weakened barrier, the most stable improvement often comes from a combination with lipids/barriers (ceramides, fatty acids, cholesterol), and not from a humectant alone.

The "cosmetic effect": why results can seem spectacular... and then fade away

Many HA serums have an immediate effect: skin is plumper and smoother to the touch. This is due to :

• a transient increase in water in the stratum corneum,
• a surface film that temporarily reduces the sensation of dryness,
• an optical improvement (more regular micro-relief).

If, afterwards, the skin continues to lose water (high TEWL), the effect fades. This is not a product "lie": it's a logical limitation of a humectant alone.

The key point: hyaluronic acid works best "sealed".

In cosmetic practice, HA works best when :

• applied to slightly damp skin (without excess),
• then "sealed" with a cream to limit evaporation.

This strategy is particularly important in winter or in heated, dry environments. Without a protective phase, the humectant may improve comfort... but the skin quickly returns to its initial level of discomfort.

How to integrate hyaluronic acid into a PERS routine (barrier-first logic)

Morning: hydration + protection

• Gentle cleanser (or simple rinse if skin is dry)
  
• Cream adapted to hyaluronic acid (light or rich, depending on your comfort level)
• SPF50+ sun protection

Evening: comfort and repair

• Double cleansing
• HA if skin tolerates it and feels the benefits
• Barrier cream (especially if night-time tightness)

If your skin is very sensitive or fragile: first stabilize the barrier (gentle cleanser + repair cream), then reintroduce HA.

Common mistakes with hyaluronic acid

• Not applying cream afterwards: hydration may remain superficial and transitory.
• Overuse on irritated skin: discomfort isn't always "a lack of water", sometimes it's a damaged barrier.
• Believe that "lower molecular weight = better": tolerance and the complete formula are more important.

Things to remember

• Topical hyaluronic acid can improve stratum corneum hydration and comfort.
• Its effect may appear highly visible, as it smoothes the micro-relief and temporarily plumps up the skin.
• It does not replace a barrier strategy: for a lasting result, it is often preferable to seal it with a suitable cream.
• The "best" HA depends on the formula, your tolerance and the context (winter, dry air, sensitized skin).

Scientific sources

• Papakonstantinou E, Roth M, Karakiulakis G. Hyaluronic acid: A key molecule in skin aging (2012).
• Pavicic T et al. Efficacy of cream-based novel formulations of hyaluronic acid of different molecular weights in anti-wrinkle treatment. (2011).
• Bukhari SN et al. Hyaluronic acid, a promising skin rejuvenating biomedicine: A review of recent updates and pre-clinical and clinical investigations. (2018).
• Passeron T et al. Clinical and biological impact of the exposome on the skin (barrier and hydration context). (2020).