Free hyaluronic acid: what it is in the filler gel
Quick facts
- Definition
- Hyaluronic acid chains present in the gel without being bound to the cross-linked network.
- Contrast
- The cross-linked fraction forms the gel that gives volume and lasts longer.
- Role
- Helps with flow and injection, and is absorbed more quickly.
- Where it comes up
- In discussions about early swelling, texture and longevity.
- Caution
- The exact proportion varies by product and should not be inferred without information from the manufacturer.
Free hyaluronic acid is the part of the product that sits in the gel without having been bound to the cross-linking network. A hyaluronic acid dermal filler is not only a cross-linked network: it usually also contains loose chains, which are part of the formula.
How do the two fractions differ?
| Fraction | How it behaves |
|---|---|
| Cross-linked | Forms the gel, supports the volume and is broken down more slowly |
| Free | Gives the mixture flow and is metabolized faster |
The free part helps lubricate the gel and makes it easier to pass through the needle or cannula. Tissue support comes from the cross-linked network, measured with parameters such as G prime.
Why does the topic come up in the clinic?
When a patient has swelling in the first days, the conversation often touches on the product's hydrophilicity. Hyaluronic acid attracts water, and that effect is part of the explanation for early swelling. The free fraction, being absorbed quickly, may contribute to how things look in the first days, but it is not the only explanation: swelling also depends on technique, area and patient.
What cannot be claimed?
There is no simple rule like "more free fraction means more swelling" or "it lasts more or less." The breakdown of the implant depends on several factors. Avoid promising the patient a timeline or an appearance based on this single piece of data.
The choice of product, volume and area is the decision of the qualified professional, according to the rules of their professional council in Brazil, and hyaluronidase should be available whenever hyaluronic acid is used.
Also known as: free HA, non-cross-linked fraction.
Frequently asked questions
Does free hyaluronic acid make filler last less?
The free fraction plays a short-lived role. How long the effect lasts depends mostly on the cross-linked part, as well as on the area, the volume and the patient.