A major advantage of hyaluronic acid fillers over permanent filling materials is that they are reversible. The enzyme hyaluronidase breaks down the hyaluronic acid, and the body clears the fragments. A review by the Italian Society of Aesthetic Medicine (Agorà), published in the Journal of Clinical Medicine in December 2025, summarises the current state of knowledge.
When is a filler dissolved?
- Nodules or palpable lumps
- Overcorrection, asymmetry or an unwanted Tyndall effect (bluish tinge when filler has been placed too superficially)
- Filler migration
- Vascular complications – here as an emergency with considerably higher doses (see our article on vascular occlusion)
Which products are available?
Most hyaluronidases used worldwide are derived from cattle or sheep. They are readily available but carry a higher risk of allergy. Recombinant human hyaluronidase is purer and is considered more favourable in terms of allergy but is available in only a few countries. The products also differ significantly in their enzyme content (e.g. 150, 200 or 1,500 units per ampoule) – an important point for dosing.
How is it dosed?
For aesthetic corrections, 5 to 150 units are usually used, depending on the region and the filler. Examples from expert recommendations:
- nose and perioral region: 15–30 units
- under the eye: 10–15 units
- eyelids: considerably less (1.5–4.5 units)
As a rule of thumb, the paper gives 50–150 units per millilitre of filler; highly cross-linked products may require considerably more. Some fillers dissolve within minutes to hours, others only after up to 24 hours. Ultrasound guidance helps to locate the filler precisely and reduce the dose.
How high is the risk of allergy?
Allergic reactions are rare; the review gives estimates of 0.05 to 0.7 %. Most are immediate reactions; delayed reactions are rare. There is an increased risk in people with wasp venom allergy, as insect venom also contains hyaluronidase. Anyone who has previously had a severe reaction to hyaluronidase or insect stings should undergo allergy testing before treatment. Whether a skin test should be carried out before every treatment is disputed among experts; there is no validated test.
The legal situation
Hyaluronidase is not approved for aesthetic use by the European Medicines Agency. It is used “off-label” – i.e. outside its approval – and requires particularly careful patient information. In Germany, one product is approved for anaesthesia. In other countries, such as Italy, preparations compounded in pharmacies are used.
Conclusion
Dissolving hyaluronic acid fillers is an established and usually well-tolerated procedure – provided it is carried out by a doctor, with appropriate dosing and after information about the risk of allergy. The authors call for standardised protocols based on controlled trials.
Note: This article is for general information only and does not replace medical advice.
