Hyaluronic acid has become one of the most popular skincare ingredients in the world — and for good reason. But as every brand rushes to put it in a serum, the quality and effectiveness of HA products varies enormously. Here’s an honest guide to what hyaluronic acid actually does, and how to choose a formula that genuinely delivers for Irish skin.
What Does Hyaluronic Acid Actually Do?
Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan found in the skin, connective tissue, and eyes. It’s what gives young skin that characteristic plumpness and bounce — but our bodies produce less of it as we age, and environmental stressors like UV exposure and pollution accelerate this decline. Topically applied HA works as a humectant: it attracts and holds water molecules, pulling moisture into the skin and temporarily plumping fine lines and improving skin texture.
Research published in the Journal of Clinical and Aesthetic Dermatology confirms that topical hyaluronic acid significantly improves skin hydration, elasticity, and the appearance of wrinkles within eight weeks of consistent use. One gram of hyaluronic acid can theoretically hold up to six litres of water — making it one of the most effective hydrating actives available at any price point.
Why Molecular Weight Matters — A Lot
Not all hyaluronic acid is the same. The molecule comes in different sizes, known as molecular weights, and this determines how deeply it can penetrate the skin:
- High molecular weight HA — larger molecules that sit on the surface of the skin. They create an immediate plumping and smoothing effect and help prevent moisture loss. Great for that instant “glass skin” look.
- Low molecular weight HA — smaller molecules that can penetrate more deeply into the epidermis, delivering longer-lasting hydration at a deeper level.
- Hydrolysed HA — a further broken-down form of the molecule with even smaller particles for deeper penetration.
The best hyaluronic acid serums include multiple molecular weights — often listed as “sodium hyaluronate” (a salt form of HA with smaller molecules) alongside standard hyaluronic acid. A single molecular weight gives you surface-level results; multiple weights work across different skin depths for more comprehensive hydration. A systematic review in Dermatology and Therapy found that low-molecular-weight HA provides measurably superior skin hydration and anti-wrinkle effects compared to high-molecular-weight forms alone.
Using HA in Irish Conditions: The Humidity Factor
One aspect of HA that’s especially relevant to Irish skincare is how it behaves in low-humidity environments. HA attracts water from its surroundings — ideally from ambient air moisture. In humid coastal Irish summers, this works extremely well. However, in a centrally heated Dublin flat in January, when indoor air humidity can drop to 20–30%, HA applied to dry skin can actually draw water from the deeper layers of the dermis rather than from the air, temporarily worsening tightness.
The solution is simple and effective: apply your HA serum to slightly damp skin, or use it after a hydrating toner or facial mist. A spritz before application ensures the HA has surface moisture to bind and hold, rather than mining from below. Always follow with a moisturiser to occlude the hydration in. See our guide to Toners for Irish Skin for complementary layering options.
What to Look For in a Good HA Serum
When evaluating a hyaluronic acid serum, here’s what separates a genuinely effective formula from a product that’s simply riding the ingredient’s popularity:
- HA appears near the top of the ingredient list — concentration matters. If hyaluronic acid or sodium hyaluronate is listed 15th on the INCI list, it’s present in negligible amounts.
- Multiple molecular weights — look for both “hyaluronic acid” and “sodium hyaluronate” in the ingredient list for a multi-depth effect.
- Supporting humectants — glycerin and panthenol alongside HA improve and sustain the hydrating effect. Nordic botanical sources like birch sap xylitol add additional humectant benefit with antioxidant properties.
- Clean, minimal formula — unnecessary synthetic fillers, alcohol (ethanol), and synthetic fragrance can undermine the skin barrier and negate the benefits of the HA.
What to Avoid
Some HA serums are poorly formulated despite strong marketing claims. Watch out for:
- High concentrations of drying alcohol (ethanol, alcohol denat) — these may help the serum absorb quickly but they strip the skin barrier over time, working against the HA’s hydrating purpose.
- Heavy synthetic fragrance — particularly if you have sensitive or reactive skin. The American Academy of Dermatology identifies fragrance as the most common cause of skincare-related contact dermatitis. A serum marketed as “calming” or “hydrating” that contains fragrance high in the INCI list is a formulation contradiction.
- HA as a marketing claim only — if HA appears very low in the ingredient list, it’s present in amounts too small to make a meaningful difference.
How to Use a Hyaluronic Acid Serum: Step by Step
For best results, incorporate your HA serum as the first active step after cleansing and toning. Apply 2–3 drops to slightly damp skin and press — don’t rub — gently into the skin. Follow immediately with your moisturiser to seal the hydration in. In the morning, your HA serum goes under your moisturiser, which goes under your SPF. At night, use it before your treatment actives (retinol, bakuchiol, or peptide serums).
For a complete guide to the role of HA in the broader skincare routine, see our article on Hyaluronic Acid Serum: What It Is and How to Use It. And for guidance on which moisturiser to follow with, see our Face Cream vs Face Moisturiser guide.
Our Serum Picks
Our Nordic serum range features clean, botanical formulations that support skin hydration without synthetic shortcuts:
- RECALM Soothing & Repairing Face Oil Serum by Nörre Nordic — a deeply hydrating Finnish botanical oil serum for dry and sensitive skin, crafted from natural and organic ingredients.
- Face It Organic Serum by True Organic of Sweden — an award-winning certified organic serum with hydrating and antioxidant actives.
Explore the full serums collection for more options.
Frequently Asked Questions
Can hyaluronic acid cause breakouts?
Pure hyaluronic acid is non-comedogenic and unlikely to cause breakouts. If a serum is causing breakouts, other ingredients in the formula — such as oils or silicones — are more likely to blame. Check the ingredient list for pore-clogging components if you’re experiencing congestion after using an HA serum.
Should I use hyaluronic acid morning or night?
Both — HA is gentle enough for twice-daily use. In the morning, it provides an excellent hydrating base under SPF. At night, it works alongside your other treatment products to support skin repair and renewal.
Is hyaluronic acid serum suitable for oily skin?
Yes. Hyaluronic acid adds water, not oil, making it ideal for oily and acne-prone skin types that still need hydration. Look for lightweight, oil-free HA serums. Properly hydrated oily skin often produces less excess sebum over time, not more.
How long does hyaluronic acid take to work?
The surface hydration effect is visible within minutes of application. For more sustained improvements in skin plumpness, fine line appearance, and texture, allow 8–12 weeks of consistent use. Consistency matters far more than concentration for long-term results.
Can I use hyaluronic acid with retinol?
Yes — and it’s actually recommended. Retinol and bakuchiol can be drying or slightly irritating, particularly during the first few weeks of use. Applying a hydrating HA serum before your retinol step helps buffer the skin, maintaining hydration and reducing the risk of irritation. See our full guide to Anti-Ageing Serums for how to layer effectively.