Hyaluronic acid: two things, one name
Hyaluronic acid in a moisturiser sits on the skin's surface and holds water there for a few hours, while hyaluronic acid used as a dermal filler is chemically cross-linked and injected under the skin, where it takes about 3 to 12 months to break down. Both start from the same molecule, the one your body already makes in its connective tissue, but cross-linking, injection depth and two different sets of EU rules turn them into separate products. A cream never reaches deep enough to lift a wrinkle; only the injected form does that.
What the molecule does inside the body
Hyaluronic acid is a sugar chain the body makes itself, mostly in connective tissue, and its defining trick is holding water: a single molecule can carry up to 1,000 times its own weight. Skin keeps a large share of the total supply, roughly half of it by some estimates, and within skin the dermis holds far more than the epidermis, with the upper, papillary layer of the dermis richer in it than the deeper reticular layer underneath.
That distribution changes with age. Research on ageing skin describes the epidermal store as the part that thins fastest and most visibly, while the dermis keeps more of its supply for longer; the hyaluronic acid that does remain also breaks down into shorter chains over time. That decline, not a marketing claim, is the biological reason a whole industry sells products promising to top the molecule back up.
Most cosmetic products use the salt form, sodium hyaluronate, because it dissolves more easily in water; it behaves the same way once it is on the skin. Swallowed forms take a different route: an oral supplement sold at a typical 120 to 240 milligrams a day has to survive digestion first, and most large polysaccharides are broken into small fragments before any of it reaches the bloodstream, so whatever benefit a capsule has does not depend on delivering an intact molecule to the dermis.
| Point | In a cream | As a filler |
|---|---|---|
| Form | not cross-linked | chemically cross-linked |
| Where it acts | skin surface and outer stratum corneum | dermis or deeper, depending on depth |
| Molecular weight used | about 50,000 to over 1,000,000 daltons | similar starting weight, then stabilised |
| Visible result | within minutes, fades within hours | immediate, fades over 3 to 12 months |
| EU classification | cosmetic product under Regulation 1223/2009 | medical device under Regulation 2017/745, Annex XVI |
| Reversible | washes off with cleansing | yes, with the enzyme hyaluronidase |
| Typical amount | a pea-sized dab per area | 1 to 4 millilitres per session |
Why a cream stops at the surface
Size decides how far any ingredient travels. The outer skin barrier lets almost nothing through once a molecule weighs more than about 500 daltons, and hyaluronic acid used in skincare typically runs from around 50,000 daltons up to well over 1,000,000. Formulas marketed as low molecular weight, often under 50,000 daltons, reach a little further into the dead surface layer, the stratum corneum, than the larger versions do. None of them reach the dermis, which is where the natural supply sits and where a wrinkle would need to be filled from below.
In practice this means a cream plumps the surface for a matter of hours, then needs reapplying, and it fills no wrinkle. Finished formulas commonly list sodium hyaluronate at 0.1 to 2 per cent of total weight, and some combine two or three molecular weights in one bottle so the water-binding effect works at more than one depth of the dead surface layer at once.
Checking where an ingredient sits on the label still matters: Article 19 of Regulation (EC) No 1223/2009 requires every ingredient to be listed in descending order of weight down to 1 per cent, so a headline ingredient printed after the preservatives is present only in a trace. The Ingredient Decoder reads a list like that for you.
The filler is built as a different product
For injection, hyaluronic acid is cross-linked, meaning it is chemically stabilised so the body cannot clear it within days the way it clears the natural molecule. It is placed at different depths depending on the goal: closer to the surface for a fine line, deeper for volume. Since the EU brought products without a medical purpose that carry medical-device risks under full oversight, hyaluronic acid fillers fall under Annex XVI, Group 3 of Regulation (EU) 2017/745 on medical devices, with common specifications under Regulation (EU) 2022/2346 that have applied since 22 June 2023.
Results are reabsorbed over roughly 3 to 12 months depending on the product and the site, after which the material is gone and another session is needed to keep the same look. A typical syringe holds 1 millilitre, and a session commonly uses 1 to 4 millilitres depending on the area treated. One advantage hyaluronic acid has over most other filler substances is that it can be dissolved early, within hours, if the injector uses the enzyme hyaluronidase.
Cross-linked hyaluronic acid has been used this way commercially since the early 2000s, which is why it has largely displaced older, non-reversible filler materials for most facial work. Clinics commonly book a review appointment at around 2 weeks, once any swelling has settled, to check symmetry and decide whether a small top-up is needed; that review, not the injection day itself, is when the final result is judged.
Questions worth asking before either one
Before buying a cream: where hyaluronic acid sits on the ingredient list, and whether the packaging is an airtight pump rather than an open jar that lets the formula dry out on contact with air. Before an injection: which product is being used, how many millilitres, who is doing the injecting, and what the plan is if a blood vessel gets blocked by accident. That last question separates a prepared injector from one who is not, and it is worth a direct answer before you agree to anything.
Injections are normally postponed for an active infection at the treatment site, a known allergy to the product, and pregnancy. Afterwards, some swelling and small bruises at the injection points are normal for a few days, and strenuous exercise, sauna and sun exposure are usually best left for about 48 hours.
For a cream, the equivalent caution is simpler: patch-test a new product on the inner forearm for 24 to 48 hours before applying it to the face, since fragrance and preservatives in a hyaluronic acid formula, not the hyaluronic acid itself, cause most reactions. Neither product replaces the other, and a routine that pairs a daily cream with an occasional injection is treating two different problems, not one.
Before you book an injection
- Which product and how many millilitres will be used for the area you want treated?
- Who is doing the injecting, and what is their plan for a blocked blood vessel?
- Do you have an active infection at the site, a known allergy, or are you pregnant?
- How long should you avoid exercise, sauna and sun afterwards?
- How long is this specific product expected to last, in months?
Frequently asked
Does hyaluronic acid in a cream fill wrinkles?
No. The skin barrier lets almost nothing through above about 500 daltons, and cosmetic hyaluronic acid weighs far more than that, so it stays on the surface or reaches a little into the stratum corneum at most. A wrinkle needs the injected, cross-linked form instead.
How long does a hyaluronic acid filler last?
Typically about 3 to 12 months, depending on the product, how heavily it is cross-linked and where it sits, after which the body has broken it down completely. Many people book a follow-up session before that point to keep the same result.
Can a hyaluronic acid filler be reversed?
Yes. Unlike most other filler materials, it can be dissolved within hours using the enzyme hyaluronidase, which is one reason it remains the most used filler substance.
Is a dermal filler a medicine or a cosmetic?
Neither in the strict sense. Under EU rules it is classed as a medical device, specifically an Annex XVI product without an intended medical purpose, and it must meet common specifications that have applied since 22 June 2023.
What is normal to notice after an injection?
Some swelling and small bruises at the injection points for a few days are typical and usually settle on their own. Most clinics advise against strenuous exercise, sauna and sun exposure for around 48 hours afterwards.
Who should not get filler injections?
Anyone with an active infection at the treatment site, a known allergy to the product, or who is pregnant should wait. Mention any bleeding disorder or history of cold sores to the injector beforehand.
Sources
- Regulation (EC) No 1223/2009 on cosmetic products, Article 19 (labelling) · ingredients listed in descending order of weight down to 1 per cent
- Regulation (EU) 2017/745 on medical devices, Annex XVI (products without an intended medical purpose) · Group 3 covers substances for facial and dermal filling by injection, regulated as medical devices; common specifications under Regulation (EU) 2022/2346 apply from 22 June 2023
- DermNet, Dermal fillers and augmentation procedures · hyaluronic acid fillers reabsorbed over about 3 to 12 months, reversal with hyaluronidase
- Papakonstantinou E et al., Hyaluronic acid: a key molecule in skin aging, Dermato-Endocrinology 2012 · skin holds about half the body's hyaluronic acid, epidermal loss and shorter polymer chains with age
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This guide is for general information. It does not replace medical or professional cosmetic advice or an examination.