What hyaluronic acid actually does.

Hyaluronic acid is probably the most ubiquitous ingredient in modern skincare. It appears in serums, moisturisers, toners, and eye creams across every price point. Understanding what it actually does — and what it does not — is more useful than the marketing claims that surround it.

What hyaluronic acid is

Hyaluronic acid is a polysaccharide — a type of molecule found naturally throughout the body, most concentrated in connective tissue, synovial fluid, and the extracellular matrix of the skin. The skin produces its own supply, though production declines with age and cumulative sun exposure. It is biocompatible, non-sensitising for the vast majority of people, and has a well-established safety profile.

What it does

Hyaluronic acid is a humectant. Its function is to draw moisture from the environment — or from the deeper layers of the skin — and hold it at the surface. The often-cited claim is that a single molecule can hold up to 1,000 times its weight in water. This is technically true, but it is also where the oversimplification begins.

Molecular weight determines penetration. Hyaluronic acid used in skincare exists at different molecular weights. High-molecular-weight HA stays on the skin surface — it forms a film that temporarily reduces moisture loss and leaves skin feeling smoother. Low-molecular-weight HA penetrates more deeply and has been studied for its interaction with deeper skin structures. Mid-weight and mixed-weight formulations are most common in practice.

It requires a sealing step. In low-humidity conditions, humectants can draw moisture from the deeper layers of the skin rather than from the air — potentially increasing transepidermal water loss in some users. A moisturiser or occlusive applied over a hyaluronic acid serum seals the moisture in. Applied alone in a dry climate, the benefit may be reduced.

What it will not do

Hyaluronic acid does not strengthen the skin barrier in the way ceramides or fatty acids do. It does not treat pigmentation, regulate oil production, or reduce the appearance of post-inflammatory marks. It is a hydration ingredient: it holds water at or near the skin surface, temporarily plumps the appearance of fine lines, and improves texture — reliably and quickly. These are real benefits. They are not dramatic ones.

A note on the L&G moisturiser

The Lux & Glo moisturiser uses squalane rather than hyaluronic acid as its primary moisturising agent. The reasoning is specific to the formula: squalane structurally resembles the skin's own sebum and reinforces the lipid matrix of the barrier directly. It does not depend on humidity. Paired with shea butter and avocado oil, it achieves both rapid absorption and sustained moisture retention without the environmental variability that humectants introduce.

This is not a position against hyaluronic acid — it is a well-studied, broadly tolerated ingredient with clear uses. It is a choice about what best serves a ritual designed to support the barrier rather than supplement it with external hydration.

Understanding the ingredients in your routine — what they actually do and do not do — is more useful than trusting the label.