Everything You Really Need to Know About Hyaluronic Acid

Curated by Claudia Shannon / Research Scientist / ishonest

Hyaluronic acid has earned a permanent place in many a skincare routine, and for seemingly good reason: this natural humectant is second to none when it comes to hydrating skin. But what exactly is hyaluronic acid, and how does it work? Here, the experts reveal everything you need to know, including the correct (and incorrect) ways to apply a hyaluronic acid product, and the formulas that do it best.

What is hyaluronic acid?

HA is a sugar molecule and a natural humectant. It's superior in terms of its ability to draw in water and hold it in the skin. 'Hyaluronic acid is a naturally occurring substance in our skin and joints that decreases as we age', explains aesthetic doctor Dr Barbara Sturm. This accounts for the skin's tendency towards dryness as we get older. Although hyaluronic acid (HA) has 'acid' in its name, it has none of the exfoliating properties associated with other cosmetic acids.

How does it work?

HA works to retain moisture in the skin thanks to its capacity to hold water (one gram of hyaluronic acid can hold six litres of H2O). That said, there has been some controversy around the actual merit HA has on skin hydration; sceptics wager that the HA molecules in skincare products are too large to penetrate the dermis, and that it needs to be delivered into the skin (via a treatment such as microneedling or mesotherapy) if it is to be truly beneficial. A-list facialist Dr Frances Prenna Jones is an advocate of the mesotherapy option. 'Some facials use ultrasound waves to help HA absorb, but optimum penetration is achieved by directly injecting it into the dermis', she says. However, innovation has allowed product formulators to side-step this absorption issue, dissecting the original molecule into shorter-chain derivatives that can penetrate the outermost layer of the skin.

What are the benefits?

Regardless of how deeply your HA product can penetrate, 'it is an important part of a daily beauty routine because even binding water to the surface of the skin keeps it moist and fresh', says Sturm. Improving the water content in the skin strengthens its barrier, calms irritation and (temporarily) plumps out fine lines. 'It also helps to repair inflammation, damage and environmental stress', she adds. 'The immediate cosmetic effect is amazing too it's wonderful under make-up.' HA in its original state and molecular weight carries no risks of irritation (although you will, of course, need to consider how your product was formulated, and the other ingredients inside it).

Are all hyaluronic acids equal?

In its original state, a HA molecule is too large to penetrate the stratum corneum (the skin's outermost layer), which is why products now use broken-down forms of the molecule. In simple terms, low-weight (short-chain) HA is smaller, and therefore penetrates the skin to a deeper level, while the larger (long- chain) high-weight HA molecules are good for hydrating the surface of the skin. A product with multiple weights will work on multiple layers.

How to use hyaluronic acid correctly

Hyaluronic acid may sound like a catch-all skincare hero, but harnessing it correctly is a little more complex than many brands would have you believe. Think of HA molecule as a sponge. Able to hold over 1000 times its weight in water, it'll soak up moisture from anywhere possible. In a very humid environment, HA will pull moisture from the air but when your environment lacks humidity, it'll seek that moisture from the deeper layers of the skin, pulling it into the upper layers (where your skincare sits). If you haven't sealed in' that skincare, the moisture pulled up by your HA will then evaporate, leaving your skin more thirsty than it was before.

The solution? Apply your HA to damp skin (cue the face mist) as this will ensure there's enough water present for it to soak up. Next: always seal in your serum. By using a moisturising cream or oil on top of a hydrating HA product, you're putting on the metaphorical lid, ensuring all that hydration stays within the skin, rather than escaping into the air.

The best hyaluronic acid skincare to try now

New innovations in skincare mean that today, there are many options when it comes to using HA topically. Serums remain a classic option applied before your day cream and SPF, a hyaluronic acid serum will soak into the skin, delivering day-long hydration benefits. However, hyaluronic acid is no longer solely reserved for serums and day creams. Face masks, targeted treatments and potent boosters are ideal for delivering an advanced hydration boost to thirsty skin there's even a self-tanner that uses plumping HA to bolster your bronze. Here, see our verdict on the very best hyaluronic acid products to try now...

The cult serum Hyaluronic Serum

Yes, it's an investment, but Dr. Barbara Sturm's cult Hyaluronic Serum is a facialist favourite for good reason. With a texture only slightly thicker than water, the formula absorbs instantly, delivering visible results as well as longer-term hydration benefits. To get the most out of it, apply to still- damp skin after cleansing, then seal in the moisture-boosting benefits with an occlusive cream or face oil.

The gentle serum B-Hydra Intensive Hydration Serum

Drunk Elephant's silky serum sees hyaluronic acid combined with pineapple- derived ceramides and provitamin B5, so it strengthens the skin barrier while hydrating beneath. A brilliant choice for skin that's easily thrown out of whack, it lends instant moisture while improving resilience and calming redness. Either apply it to damp skin before layering an oil (like this one), or mix the two products in your hand before massaging in as one.

The brightening cream Tidal Brightening Enzyme Water Cream

Proving that hydrating moisturisers don't have to be heavy, Sunday Riley's cult formulation feels as light as water on the skin. The gel-textured cream contains two different weights of hyaluronic acid, alongside resurfacing enzymes (sourced from papaya) to gradually brighten and clarify. With gentle emollients, it's the ideal one-step treatment for congestion-prone skin.

The hydrating tanner Super Glow Hyaluronic Self-Tan Serum

Tan-Luxe's custom tanning serum has been boosted with a skincare-savvy dose of hyaluronic acid. Massage a few drops directly onto your skin before your night cream to wake up with a deeper glow and plumper cheeks. There's now an SPF 30 iteration for daytime too.

The eye treatment Sarah Chapman Eye Recovery

This impressively complex eye cream combines collagen-boosting peptides with hyaluronic acid to visibly plump the under-eye area. It's deeply hydrating, yet doesn't feel heavy.

The lightweight serum Multi-Molecular Hyaluronic Complex MMHC2 [15ml]

First things first: this one does not smell good. However, if fair pricing and high performance rank higher than pampering appeal on your list of priorities, it's a no-brainer. As the overly complicated name implies, it contains multiple weights of hyaluronic acid (12 to be precise) for an all-round boost of hydration. Surprisingly, it feels as light as water on skin and works to calm inflammation, too.

The skin-strengthening serum Essential Serum

Formulated by one of London's most in-demand facial clinics, this all-in-one serum combines deep-penetrating hyaluronic acid with organic silicon (which restructures collagen fibres to make skin feel stronger) and sodium DNA to reduce inflammation. It feels incredibly gentle (as all good serums should), but packs a serious skin-boosting punch.

The booster Hyaluronic Acid Booster

Fans of fuss-free skincare will love Paula Begoun's clever booster serums. Designed for dehydrated skin, this one contains hyaluronic acid alongside barrier-rebuilding ceramides: simply blend a drop into your moisturiser of choice whenever skin feels parched.

The natural serum Hyaluron Serum

Susanne Kaufmann's natural serum has a refreshingly short ingredient list: plant-derived hyaluronic acid, a touch of water, and all-natural preservatives and fragrances. To call it a potent hydrator would be an understatement.

The multi-benefit serum Triple Hyaluronic Antioxidant Hydration Serum

Allies of Skin is loved for its precisely formulated products, designed to deliver multiple benefits in one. This complex serum combines dual-weight hyaluronic acid with a collagen-boosting peptide complex, inflammation-reducing resveratrol, clarifying niacinamide and protective antioxidants. Layer it beneath a simple moisturiser each morning.

The vegan-friendly serum The Most: Hyaluronic Super Nutrient Hydration Serum

New brand PSA is the little sister to Allies of Skin, offering more affordable treatments with no compromise on integrity. This hyaluronic serum doesn't contain the complex antioxidants and peptides as the one above, but it will hydrate and soothe just as well. Liquorice brings brightening properties, while glycerin and bisabolol will calm and moisturise. A reliable option for dehydrated skin.

The make-up prep mask Hyaluronic Marine Hydrating Modeling Mask x 4

This two-step mask is the same one used by Dr. Dennis Gross in his own professional treatments. Blend the powder and gel together, and apply to the skin to seal in a potent blend of hyaluronic acid and moisture-grabbing algae. Once dry, peel the rubbery mask away to reveal incredibly plump, juicy skin. It's the perfect pre-party treat.

The make-up primer Hyaluronic Hydra Primer

This fluffy, mousse-like primer provides the perfect canvas for any liquid foundation. Rather than mattifying the skin, which can look harsh and unflattering, it skims over fine lines and enlarged pores, creating an even and hydrated base that glows.

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