Swelling factor: what it is in hyaluronic acid fillers
Quick facts
- Definition
- A hyaluronic acid gel's ability to absorb water and increase in volume after injection.
- Cause
- The hydrophilic nature of hyaluronic acid.
- Varies with
- Concentration, crosslinking and product characteristics.
- Implication
- The final volume may differ from the injected volume.
- Caution
- Product-specific information is in the package insert and from the manufacturer.
The swelling factor is the ability of a hyaluronic acid gel to absorb water and increase in volume after it is injected. It comes from the nature of hyaluronic acid, which attracts and holds water, known as hydrophilicity. That is why the product that leaves the syringe may occupy a slightly different space in the following days.
What does the swelling factor depend on?
It is not the same in every product. Factors that tend to influence it include the concentration, the degree of crosslinking and the manufacturing process. Firmer products, used for structure, tend to behave differently from softer ones, used in thin areas. Product-specific information is in the package insert and the manufacturer's materials.
Why does it matter in practice?
Whoever plans the volume takes into account that the gel may absorb water after injection. In thin, visible areas, such as the lips and the under-eye area, a product with strong absorption capacity can give more volume than expected, which supports the logic of conservative volumes and touch-ups in stages.
Difference between swelling factor and edema
Swelling (edema) is the body's response to the trauma of the needle and to the product itself, and it usually subsides over a few days. The swelling factor is a property of the material, which acts continuously while the gel is in the tissue. The two can add up in the first days, which is why the result should only be assessed later.
What should you explain to the patient?
Agreeing on this point in the informed consent avoids surprises and anxiety.
In Harmy
The app's projection shows the estimated aesthetic effect of a volume in ml on the frontal photo. It does not simulate product properties or the settling of the gel.
Also known as: swelling factor, water absorption capacity.
Frequently asked questions
Does the swelling factor change the volume that stays in the face?
It can. Gels with a greater capacity to absorb water tend to increase a little after injection, and this is part of the professional's calculation when choosing product and volume.
Are swelling factor and swelling (edema) the same thing?
No. Edema is an inflammatory reaction of the tissue to the procedure. The swelling factor is a property of the gel itself, which absorbs water because it is hydrophilic.